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| Features * One of a Family of Devices with User Memories from 1 Kbit to 8-Kbit * EEPROM User Memory - Four or Eight Zones - Self-timed Write Cycles - Single-Byte or Multiple-Byte Page-Write Modes - Programmable Access Rights for Each Zone 2-Kbit Configuration Zone - 37-byte OTP Area for User-defined Codes - 160-byte Area for User-defined Keys and Passwords High Security Features - 64-bit Mutual Authentication Protocol (under license of ELVA) - Cryptographic Message Authentication Codes (MAC) - Stream Encryption - Four Key Sets for Authentication and Encryption - Eight Sets of Two 24-bit Passwords - Anti-tearing Function - Voltage and Frequency Monitor Embedded Application Features - Low Voltage Operation: 2.7V to 3.6V - Secure Nonvolatile Storage for Sensitive System or User Information - 2-wire Serial Interface - 1.0 MHz Compatibility for Fast Operation - Standard 8-lead Plastic Packages - Same Pinout as 2-wire Serial EEPROM's Smart Card Features - ISO 7816 Class B (3V) Operation - ISO 7816-3 Asynchronous T = 0 Protocol (Gemplus(R) Patent) - Multiple Zones, Key Sets and Passwords for Multi-application Use - Synchronous 2-wire Serial Interface for Faster Device Initialization - Programmable 8-byte Answer-To-Reset Register - ISO 7816-2 Compliant Modules High Reliability - Endurance: 100,000 Cycles - Data Retention: 10 years - ESD Protection: 2,000V * * CryptoMemory Specification for Standard Mode of Operation AT88SC0104CA AT88SC0204CA AT88SC0404CA AT88SC0808CA * * * 5221A-CRYPT-10/08 AT88SCXXXXCA Table of Contents 1 Pin Configuration and Package Information ......................................... 4 1.1 Pin Configuration .....................................................................................................4 1.2 Package Information ...............................................................................................4 2 Description ............................................................................................... 5 2.1 Differences from AT88SCxxxxC family of Products ................................................5 2.2 Embedded Applications ..........................................................................................5 2.3 Smart Card Applications ..........................................................................................5 2.4 Purpose and Scope of This Document ....................................................................5 3 4 Block Diagram .......................................................................................... 6 Pin Description ......................................................................................... 7 4.1 Supply Voltage (VCC) .............................................................................................7 4.2 Clock (SCL/CLK) .....................................................................................................7 4.3 Serial Data (SDA/IO) ...............................................................................................7 4.4 Reset (RST) ............................................................................................................7 4.5 Detailed Description ................................................................................................7 4.6 User Memory ...........................................................................................................7 4.7 Control Logic .........................................................................................................11 4.8 Configuration Memory ...........................................................................................11 5 Communication Security Modes .......................................................... 14 5.1 Security Operations ...............................................................................................14 5.2 Configuration Memory Values ...............................................................................18 5.3 SME - Supervisor Mode Enable ...........................................................................19 5.4 UCR - Unlimited Checksum Reads ......................................................................19 5.5 UAT - Unlimited Authentication Trials ...................................................................19 5.6 ETA - Eight Trials Allowed ....................................................................................19 5.7 CS0 - CS3: Programmable Chip Select (only relevant in synchronous protocol) .20 5.8 Security Fuses ......................................................................................................23 6 7 Protocol Selection ................................................................................. 25 Synchronous Protocol .......................................................................... 26 7.1 Start-up Sequence ................................................................................................26 7.2 Command Set .......................................................................................................27 7.3 Command Format .................................................................................................27 2 5221A-CRYPT-10/08 7.4 Acknowledge Polling ............................................................................................29 7.5 Device Addressing ................................................................................................30 7.6 Command Descriptions .........................................................................................30 7.7 Write User Zone: $B0 ............................................................................................31 7.8 Random read: $B1 ................................................................................................32 7.9 Read User Zone: $B2 ............................................................................................33 7.10 System Write: $B4 ...............................................................................................34 7.11 System Read: $B6 ..............................................................................................36 7.12 Verify Password: $BA ..........................................................................................37 8 Initialization Example ............................................................................ 38 8.1 Write Data to User Zones ......................................................................................38 8.2 Unlock Configuration Zone ....................................................................................38 8.3 Write Data to Configuration Zone ..........................................................................38 8.4 Set Security Fuses ................................................................................................38 9 Asynchronous T=0 Protocol ................................................................. 41 9.1 Character format ...................................................................................................41 9.2 Command format ...................................................................................................41 9.3 Command Set .......................................................................................................42 9.4 Command Descriptions .........................................................................................44 9.5 System READ: $B6 ...............................................................................................48 10 Initialization Example ............................................................................ 50 10.1 Write Data to User Zones ....................................................................................50 10.2 Unlock Configuration Zone ..................................................................................50 10.3 Write Data to Configuration Zone ........................................................................50 10.4 Set Security Fuses ..............................................................................................50 11 Absolute Maximum Ratings .................................................................. 53 11.1 DC and AC Characteristics .................................................................................54 11.2 Timing Diagrams for Synchronous Communications ..........................................55 12 Electrical Characteristics ...................................................................... 57 12.1 Tamper Detection ................................................................................................57 3 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 1. Pin Configuration and Package Information 1.1 Pin Configuration Pin Configuration Description Supply Voltage Ground Serial Clock Input Serial Data Input/Output Reset Input ISO Module Contact C1 C5 C3 C7 C2 Standard Package Pin 8 4 6 5 NC TSSOP 8 1 6 3 NC Table 1-1. Pad VCC GND SCL\CLK SDA\IO RST 1.2 Package Information CryptoMemory Packages Figure 1-1. Smart Card Module VCC=C1 RST=C2 SCL/CLK=C3 NC=C4 C5=GND C6=NC C7=SDA/IO C8=NC 8-lead SOIC, PDIP NC NC NC GND 8-lead TSSOP VCC NC SCL 1 2 3 4 8 7 6 5 NC NC SDA 1 2 3 4 8-Lead TSSOP 8 7 6 5 VCC NC SCL NC SDA GND 4 5221A-CRYPT-10/08 2. Description The AT88SCxxxxCA is a family of 4 high-performance secure memory devices providing 1K to 8K bits of user memory with advanced built-in security and cryptographic features. The memory is divided into 4 or 8 user zones each of which may be individually set with different security access rights or used together to provide space for one or multiple data files. A configuration zone contains registers to define the security rights for each user zone and space for passwords and secret keys used by the security logic of CryptoMemory. Through dynamic, symmetric-mutual authentication, data encryption, and the use of encrypted checksums, CryptoMemory provides a secure place for storage of sensitive information within a system. With its tamper protection circuits, this information remains safe even under attack. CryptoMemory also provides high security, low cost and ease of implementation of host-client type systems without the need for a microprocessor operating system. The embedded cryptographic engine provides for a dynamic, symmetric-mutual authentication between the device and host, as well as performs stream encryption for all data and passwords exchanged between the device and host. Up to four unique key sets may be used for these operations. 2.1 Differences from AT88SCxxxxC family of Products The key differentiating feature of the AT88SCxxxxCA family of memory devices from AT88SCxxxxC family is support for hardware implementation of the TWI READ command. Support for this TWI hardware command allows for faster application development and also permits greater device versatility. In addition, AT88SCxxxxCA offers a RANDOM READ command whereby given a starting address, the user can clock unlimited number of bytes from the device up to the memory capacity. Last but not least, the AT88SCxxxxCA family of devices specifically targets low voltage and low power applications. 2.2 Embedded Applications A 2-wire serial interface running at 1.0 MHz is used for fast and efficient communications with up to 15 devices that may be individually addressed. CryptoMemory is available in industry standard 8-lead packages with the same familiar pin layout as 2-wire serial EEPROM's supporting only the synchronous communications protocol. Note: TSSOP Pinout not the same. 2.3 Smart Card Applications CryptoMemory offers the ability to communicate with virtually any smart card reader using the asynchronous T=0 protocol defined in ISO 7816-3. All CryptoMemory devices in smart card module form will also communicate using a synchronous 2-wire serial interface. 2.4 Purpose and Scope of This Document This document covers only the Standard Mode of operation of CryptoMemory. The other modes of operation are the Authentication and Encryption Modes. This document provides all the information needed to utilize CryptoMemory in the Standard Mode. The scoping of this document allows for free distribution without formal requirements of any user agreements and serves the purpose of developing applications using only the Standard Mode of operation. Documents containing detailed description of the cryptographic technology, operation and function of the Authentication and Encryption Modes of CryptoMemory are secure and so only available under Non-Disclosure and Limited Licensing Agreements (NDA and LLA). Contact your local Atmel sales office to obtain these secure documents. 5 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 3. Block Diagram Authentication, Encryption and Certification Unit VCC GND Power Management Synchronous Interface SCL SDA RST Asynchronous ISO Interface Reset Block Data Transfer EEPROM Password Verification Answer to Reset 6 5221A-CRYPT-10/08 4. Pin Description 4.1 Supply Voltage (VCC) The VCC input is a 2.7V to 3.6V positive voltage supplied by the host. 4.2 Clock (SCL/CLK) In the asynchronous T=0 protocol, the SCL/CLK input is used to provide the device with a carrier frequency f. The nominal length of one bit emitted on I/O is defined as an "elementary time unit" (etu) and is equal to 372/f. When the synchronous protocol is used, the SCL/CLK input is used to clock data in on the positive clock edge and clock data out on the negative clock edge. 4.3 Serial Data (SDA/IO) The SDA pin is bi-directional for serial data transfer. This pin is open-drain driven and may be wired with any number of other open drain or open collector devices. An external pull up resistor should be connected between SDA and VCC, a nominal value of 4.7K ohm may be used. The value of this resistor and the system capacitance loading the SDA bus will determine the rise time of SDA. This rise time will determine the maximum frequency during Read operations. Low value pull up resistors will allow higher frequency operations while drawing higher average power supply current. 4.4 Reset (RST) CryptoMemory provides an ISO 7816-3 compliant asynchronous Answer-To-Reset (ATR) sequence. When the reset sequence is activated, the device will output the data programmed into the 64-bit answer to reset register. When RST is low, all internal logic, access rights and write cycles are in reset, except the asynchronous mode activation flag. A weak internal pull-up on the RST input pad allows the device to be used in synchronous mode without bonding RST. For synchronous only smart card applications an external pull-up on RST is recommended to ensure synchronous operation under any system timings or conditions. CryptoMemory does not support a synchronous answer to reset sequence. The RST input is not available in the plastic package options for CryptoMemory. 4.5 Detailed Description To enable the security features of CryptoMemory, personalize the device by setting up registers and loading appropriate passwords and keys. This is accomplished though programming the configuration zone of CryptoMemory using simple write and read commands. To gain access to the configuration zone, the secure code (write 7 password) must be successfully presented. After writing and verifying data in the configuration zone, the security fuses must be blown to lock this information in the device. For additional information on personalizing CryptoMemory, please see the examples in the protocol sections of this specification. 4.6 User Memory The EEPROM user memory is divided into 4 or 8 user zones. Multiple zones allow for the storage of different data types or files in different zones. Access to user zones is possible only after meeting security requirements. The customer defines these security requirements in the configuration zone during device personalization. When the same security requirements define access to multiple zones, the zones effectively serve as one large storage area albeit with the requirement to select each zone prior to access. 7 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Table 4-1. Zone AT88SC0104CA User Memory $0 $00 $1 $2 $3 $4 $5 $6 $7 User 0 $18 $00 32 Bytes User 1 $18 $00 32 Bytes User 2 $18 $00 32 Bytes User 3 $18 32 Bytes Note: Page size = 16 bytes. 8 5221A-CRYPT-10/08 Table 4-2. Zone AT88SC0204CA User Memory $0 $00 $1 $2 $3 $4 $5 $6 $7 User 0 $38 $00 64 Bytes User 1 $38 $00 64 Bytes User 2 $38 $00 64 Bytes User 3 $38 64 Bytes Note: Page size = 16 bytes. 9 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Table 4-3. Zone AT88SC0404CA User Memory $0 $00 $1 $2 $3 $4 $5 $6 $7 User 0 $78 $00 128 Bytes User 1 $78 $00 128 Bytes User 2 $78 $00 128 Bytes User 3 $78 128 Bytes Note: Page size = 16 bytes. 10 5221A-CRYPT-10/08 Table 4-4. Zone AT88SC0404CA User Memory $0 $00 $1 $2 $3 $4 $5 $6 $7 User 0 $78 128 Bytes User 1 User 6 $00 $78 $00 128 Bytes User 7 $78 128 Bytes Note: Page size = 16 bytes. 4.7 Control Logic Access to the user zones occurs only through the control logic built into the device. This logic is configurable through access registers, key registers and keys programmed into the configuration memory during device personalization. Also implemented in the control logic is a cryptographic engine for performing the various higher-level security functions of the device. 4.8 Configuration Memory The configuration memory consists of 2048 bits of EEPROM memory used for storing passwords, keys, codes and defining security levels to be used for each User Zone. The control logic defines access rights to the configuration memory and the user may not alter these rights. The access rights include the ability to program certain portions of the configuration memory and then lock the data written through use of Security Fuses. The configuration memory for each CryptoMemory device is identical with the exception of the number of Access Registers and Password/Key Registers available. Devices with 4 user zones have four sets of registers, and those with 8 user zones 8 sets of registers. Unused memory space in the register region becomes reserved to ensure other components of the configuration memory remain at the same address location regardless of the number of user zones in a device. 11 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Table 4-5. AT88SC0104CA, 0204CA, 0404CA Configuration Memory $0 $1 $2 $3 $4 $5 $6 $7 Information Card Manufacturer Code Read Only Lot History Code DCR AR0 PR0 AR1 Identification Number Nc PR1 AR2 PR2 AR3 PR3 Access Control $00 $08 $10 $18 $20 $28 $30 $38 $40 Fab Code MTZ Answer To Reset Reserved Issuer Code $48 $50 $58 $60 $68 Reserved for Authentication and Encryption $70 $78 $80 $88 $90 $98 Reserved for Authentication and Encryption $A0 $A8 $B0 $B8 $C0 $C8 Password $D0 $D8 $E0 $E8 $F0 Reserved $F8 Forbidden PAC Write 7 PAC Read 7 PAC PAC PAC Write 0 Write 1 Write 2 PAC PAC PAC Read 0 Read 1 Read 2 Secret Cryptography 12 5221A-CRYPT-10/08 Table 4-6. AT88SC0808CA Configuration Memory $0 $1 $2 $3 $4 $5 $6 $7 Information Card Manufacturer Code Read Only Lot History Code DCR AR0 AR4 PR0 PR4 AR1 AR5 Identification Number Nc PR1 PR5 AR2 AR6 PR2 PR6 AR3 AR7 PR3 PR7 Access Control $00 $08 $10 $18 $20 $28 $30 Fab Code MTZ Answer To Reset Reserved $38 $40 Issuer Code $48 $50 $58 $60 $68 Reserved for Authentication and Encryption $70 $78 $80 $88 $90 $98 Reserved for Authentication and Encryption $A0 $A8 $B0 $B8 $C0 $C8 $D0 $D8 $E0 $E8 $F0 Reserved $F8 PAC PAC PAC PAC PAC PAC PAC PAC Write 0 Write 1 Write 2 Write 3 Write 4 Write 5 Write 6 Write 7 PAC PAC PAC PAC PAC PAC PAC PAC Read 0 Read 1 Read 2 Read 3 Cryptography Secret Password Read 4 Read 5 Read 6 Read 7 Forbidden 13 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 5. Communication Security Modes Communication between the device and host operates in three basic modes. Standard mode is the default mode for the device after power-up. Authentication mode is activated by a successful authentication sequence. Encryption mode is activated by a successful encryption activation following a successful authentication. Data transferred to and from the device is handled per the following table. Table 5-1. Mode Standard Authentication Encryption Notes: Communication Security Modes Configuration Data clear clear clear User Data clear clear encrypted Passwords clear encrypted encrypted Data Integrity Check MDC MAC MAC 1. Configuration data includes the entire configuration memory except the passwords 2. MDC: Modification Detection Code 3. MAC: Message Authentication Code 5.1 5.1.1 Security Operations Password Verification The use of passwords protects read and write accesses to the user zones. Any one of 8 password sets is available for assignment to any user zone through configuration of access registers. CryptoMemory provides separate 24-bit passwords for read and write operations. Read passwords grant only read accesses to zones under password protection, while write passwords grant both read and write accesses. Successful presentation of any password renders the verify password command active until the presentation of another password or device reset. Only one password may be active at a time. Presenting incorrect passwords decrements the value of the corresponding password attempts counter (PAC). Decrementing the PAC to $00 permanently disables the corresponding password and permanently renders the corresponding user zone(s) under protection inaccessible. Operation in authentication or encryption modes requires encryption of passwords for all password transactions. Password Verification Figure 5-1. CryptoMemory Device Verify Password Allow access Command/Communications Verify Password Host Logic Send Password encrypted if performed after Mutual Authentication 14 5221A-CRYPT-10/08 5.1.2 Authentication Protocol The use of a mutual authentication protocol further protects access to user zones. Any one of 4 key sets is available for assignment to any user zone through configuration of access registers. Each key set consists of a secret seed, a cryptogram, and a session encryption key. A Verify Crypto command exists to allow the use of any one of the key sets to enter authentication mode. Each successful entry into authentication mode renders the mode active for the current key set until the next call to the Verify Crypto command or device reset. Only one key set may be active at anytime. Unsuccessful calls of the Verify Crypto command exits authentication mode and decrements the value of the authentication attempts counter (AAC) register. Decrementing AAC to $00 permanently disables the corresponding key set and permanently renders the corresponding user zone(s) under protection inaccessible. Entry into authentication mode is a process through which the host and CryptoMemory device mutually authenticate one another. First, the host generates a 64-bit random number, reads a current cryptogram and identification information from the device, and uses this information in conjunction with the corresponding secret seed to generate a 64-bit challenge for the device. The host also generates a new cryptogram and session encryption key in the process. The host then sends the challenge and random number to the device by calling the Verify Crypto command. The device utilizes the random number from the host to generate its own challenge, new cryptogram and session encryption key. It then compares the challenge to the one from the host. If the challenges match, then the device declares the host authentic, overwrites its corresponding current cryptogram and session encryption key with the new ones. To complete the mutual authentication, the host reads the new cryptogram from the device and compares it with its new cryptogram. The new cryptogram from the device serves as a challenge to the host. If the cryptograms match then the device is authentic. Only an authentic pair of host and device can generate the same challenges and cryptograms. Activating mutual authentication requires the use of the Verify Authentication variant of the Verify Crypto command (see 9: CryptoMemory Command Set). Figure 5-2. The Mutual Authentication Process CryptoMemory Device Device Info, Cryptogram [Secret Seed] Command/Communications Read Config Zone Host Logic Read Device Info, Cryptogram Compute Secret Seed Generate Random Number Compute Challenge A Verify Challenge A Compute Challenge B Verify Authentication Compute Challenge A Compute Challenge B Compute Session Key Read Config Zone Compute Session Key Allow Access Read Chellenge B Verify Chellenge B Allow Access 15 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 5.1.3 Data Encryption CryptoMemory allows the use of encryption between a host system and the CryptoMemory device to protect the confidentiality of data during read-write accesses and verify password operations. To enable encryption, the host must generate a challenge using the session encryption key generated from the authentication activation step. The host then needs to call the Verify Crypto command again with the device still in active authentication mode. The session encryption key must belong to the active authentication key set. The host may enable encryption at anytime after which data content of communication between host and device user zones becomes encrypted. If a user zone configuration in the Access Register requires encryption, however, then the host must enter encryption mode and must encrypt all data content to and from the zone in the remainder of the active encryption session in order to communicate with the zone. CryptoMemory does not encrypt system zone data except for password and password attempt counters. Passwords and password attempt counters require encryption during active authentication or encryption modes. Each successful entry into encryption mode renders the mode active for the current key set until the next call to the Verify Crypto command or device reset. Only one key set may be active at anytime. Unsuccessful calls of the Verify Crypto command exits both encryption and authentication modes and decrements the value of the authentication attempts counter (AAC) register. Decrementing AAC to $00 permanently disables the corresponding key set and permanently renders the corresponding user zone(s) under protection inaccessible. Activating encryption is similar in process to activating authentication with the exception that the session encryption key replaces the secret seed. The process uses the Verify Encryption variant of the Verify Crypto command (see 9: CryptoMemory Command Set). Figure 5-3. Encryption Activation Process from Active Authentication Mode CryptoMemory Device Command/Communications Host Logic Session Key, Cryptogram Generate Random Number Session Key, Cryptogram Compute Challenge A Verify Challenge A Compute Challenge B Enable Encryption Read Config Zone Verify Encryption Compute Challenge A Compute Challenge B Read Challenge B Verify Challenge B 16 5221A-CRYPT-10/08 5.1.4 Encrypted Checksum (Message Authentication Code, MAC) CryptoMemory implements a data validity check function in the form of an encrypted checksum. This checksum provides a bi-directional data integrity check and data origin authentication capability in the form of a Message Authentication Code (MAC): only the host/device that carried out a valid authentication is capable of computing a valid MAC. When writing data to the CryptoMemory device in authentication or encryption communication modes, the host must send a valid checksum immediately following the write command. If the checksum is invalid, the device rejects the write command and resets the device security privileges. The host must reinitiate entry into authentication and, if applicable, encryption modes to continue. The use of checksum is optional when reading data. Calls to the read checksum command resets device security so its use is recommended only at the completion of all data read operations from the device. Data Protection Features Security operations control access to data stored in CryptoMemory. After gaining access, additional options exist to protect data in the user memory. Modify Forbidden The Modify Forbidden option renders the user zone read-only by restricting all write operations to it. It is recommended to program all required data in the user zone prior to enabling this option. Modify Forbidden is available for any user zone and is selectable by configuring appropriate Access Registers. Program Only The Program Only option constrains data bit modification to programming from logic "1" to logic "0" only. Data bits may never change from logic "0" to logic "1". Program Only is available for any user zone and is selectable by configuring appropriate Access Registers. 5.1.5 5.1.6 5.1.7 5.1.8 Write Lock The Write Lock option provides ability to render individual bytes within a user zone read-only by restricting all write operations to it. It operates on 8-byte page level whereby the lowest addressed byte of the page serves as the write access control byte for that page. Figure 5 shows the use of write lock for data at addresses $080 - $087. The byte at $080 controls writeaccess to bytes from $080 to $087. Figure 5-4. Address $080 Write Lock Example $0 1101 1001 $1 xxxx xxxx locked $2 xxxx xxxx locked $3 xxxx xxxx $4 xxxx xxxx $5 xxxx xxxx locked $6 xxxx xxxx $7 xxxx xxxx The Write Lock option also applies to the access control byte for each page by writing its least significant (rightmost) bit to logic "0". Moreover, only logic modifications from logic "1" to logic "0" of the access control byte are permissible. Write Lock is available for any user zone and is selectable by configuring appropriate access registers. Furthermore, configuring a user zone with the Write Lock option restricts writing to that zone to a byte at a time. Attempts to write several bytes within a command results in writing only the first byte. 17 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 5.1.9 Anti-tearing (Power Loss Protection) In the event of a power loss during a write cycle, the integrity of the device's stored data may be recovered. This function is optional and the host may choose to activate the anti-tearing function for any write to a user zone or configuration zone by use of the appropriate B4 system write command. When anti-tearing is active, write commands will take longer to execute since more write cycles are required. Additionally, the data written is limited to 8 bytes. Data is written first to a buffer zone in EEPROM instead of the intended destination address in the user zone or configuration zone, but with the same access conditions. If this write cycle is interrupted the original data remains in tact in the user zone or configuration zone. The data is then written in the required memory location. If this second write cycle is interrupted the device will automatically recover the data from the system buffer zone at the next power-up and write it to the intended destination address. In two-wire mode, the host is required to perform ack polling for 36ms after write commands when anti-tearing is active. At power-up five clock cycles are required to check the anti-tearing flags. In the event that the device needs to carry out the data recovery process the host is required to perform ack polling for 18ms. 5.2 Configuration Memory Values This section describes each individual field in the configuration memory. 5.2.1 Default Values Atmel programs certain fields of the system zone at the factory. The customer may elect to change the content of all of these fields except for the Lot History Code field, which is permanently locked. Atmel programs the remainder of the fields, including all of the configuration memory and user zones to ones prior to releasing the device from the factory. Table 2: Factory Programmed Fields2 summarizes device fields Atmel programs at the factory. A brief description of each field follows. Table 5-2. Device AT88SC0104CA AT88SC0204CA AT88SC0404CA AT88SC0808CA Factory Programmed Fields ATR 3B B2 11 00 10 80 00 01 3B B2 11 00 10 80 00 02 3B B2 11 00 10 80 00 04 3B B2 11 00 10 80 00 08 Fab Code 10 10 20 20 40 40 80 80 Lot History Code Variable, Locked Variable, Locked Variable, Locked Variable, Locked Write 7 Password (Secure Code) DD 42 97 E5 47 47 60 57 34 22 E8 3F 5.2.2 Answer To Reset (ATR) This is an 8 byte wide register with content that Atmel defines. This register is read/write accessible prior to blowing the FAB fuse, but becomes read-only after blowing the fuse. Fab Code This field is a 16-bit wide register with content that Atmel defines. This field is read/write accessible prior to blowing the FAB fuse, but becomes read-only after blowing the fuse. 5.2.3 5.2.4 Memory Test Zone (MTZ) This field is a 16-bit wide register with open read/write access privileges at all times for testing basic communication to the device. This field is free of all security constraints at all times. 18 5221A-CRYPT-10/08 5.2.5 Card Manufacturer Code This field is a 32-bit wide register with read/write access privileges for the customer to define its content. The content of this field becomes read-only after blowing the PER fuse. Figure 8: Device Fuses 5.2.6 Lot History Code This field is a 64-bit wide register with content that Atmel defines. This field is read-only. Issuer Code This field is a 128-bit wide register with read/write access privileges for customer to define its content. The content of this field becomes read-only after blowing the PER fuse. 5.2.7 5.2.8 Device Configuration Register (DCR) This 8-bit register allows selection of the following device configuration options (active low). The values programmed have an immediate affect on the logic of the device. The default value is "1" for each bit. Figure 5-5. BIT 7 SME DCR Register Bit Map BIT 6 UCR BIT 5 UAT BIT 4 ETA BIT 3 CS3 BIT 2 CS2 BIT 1 CS1 BIT 0 CS0 5.3 SME - Supervisor Mode Enable Asserting this bit (SME = "0") enables supervisor mode for Write Password 7 such that verifying password 7 grants read and write access to all passwords sets and PACs. Verifying Write Password 7 does not grant access to other passwords when this bit is not asserted (SME = "1"). 5.4 UCR - Unlimited Checksum Reads Asserting this bit (UCR = "0") allows unlimited number of checksum reads without requiring a new authentication. Not asserting this bit (UCR = "1") limits the read of checksum to one attempt after which the devices resets the crypto algorithm after executing the Read Checksum command. 5.5 UAT - Unlimited Authentication Trials Asserting this bit (UAT = "0") disables the Authentication Attempts Counter (AAC) thus allowing unlimited authentication attempts. The AAC decrements after each unsuccessful attempt but the internal logic ignores it value. Asserting this bit also prevents reset of the crypto algorithm after reading the MAC in encryption mode. The UAT bit does not affect the Password Attempts Counter. 5.6 ETA - Eight Trials Allowed Asserting this bit (ETA = "0") extends the trials limit to 8 incorrect attempts to authenticate or verify a password. The counter (AAC or PAC) will decrement ($FF, $FE, $FC, $F8, $F0, $E0, $C0, $80, $00) with each incorrect attempt. Disabling this bit (ETA = "1") limits authentication and password verification trials to only four incorrect attempts ($FF, $EE, $CC, $88, $00). 19 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 5.7 CS0 - CS3: Programmable Chip Select (only relevant in synchronous protocol) The four most significant bits (b4 - b7) of every command comprise the Chip Select Address. All CryptoMemory devices will respond to the default Chip Select Address of $B (1011). Each device also responds to a second Chip Select Address programmed into CS0-CS3 of the Device Configuration Register. By programming each device to a unique Chip Select Address, it is possible to connect up to 15 devices on the same Serial Data bus and communicate individually to each. Global communications to all devices sharing the bus is accomplished using the default Chip Select Address $B. 5.7.1 Access Registers Figure 4: Access Register Bit Map Four, eight, or sixteen 8-bit access registers allow personalization of the device. Each access register works in conjunction with a Password/Key register to define the security settings for each individual zone of the user memory. Values in the access registers take immediate effect after programming. The default value for each bit is "1". Figure 5-6. BIT 7 PM1 Access Register Bit Map BIT 6 PM0 BIT 5 AM1 BIT 4 AM0 BIT 3 ER BIT 2 WLM BIT 1 MDF BIT 0 PGO 5.7.1.1 PM(1:0) Password Mode Table 5-3. PM1 1 1 0 Password Mode PM0 1 0 * Access No Password Required Write Password Required Read and Write Passwords Required When PM = "11", the user zone under protection requires no password. When PM = "10", the zone requires Write Password verification for writing and reading is free. When PM = "01" or "00", reading requires the read password verification and writing requires write password verification. However, proper verification of the Write Password also grants read access. The password set required is specified by PW(3:0) in the corresponding Passwords/Keys Register (see following section). Verification of the write password also allows modification of the read and the write passwords. 5.7.1.2 AM(1:0) - Authentication mode Table 5-4. PM1 1 1 0 0 Authentication Mode PM0 1 0 1 0 Access No Authentication Required Authentication for Write Normal Authentication Mode Dual Access Mode 20 5221A-CRYPT-10/08 When AM = "11", the user zone under protection requires no authentication. When AM = "10", the zone requires authentication only for write accesses and read accesses are free. When AM = "01", the zone requires authentication for both write and read accesses. In both of these configurations, the Authentication Key (AK) in the corresponding Passwords/Keys Register specifies the required Secret Seed (see following section). Finally, when AM = "00", the dual access mode is active in which authentication using the Program Only Key (POK) gives a right to read and program the zone (i.e. write '0's only), while authentication using the Authentication Key (AK) gives full read and write access to the zone. In this way, a token application may be implemented, whereby regular hosts with knowledge of POK may decrement the stored value, and only master hosts with knowledge of AK may reset the token to its full value. Please see the following section on the Passwords/Keys Register for further definition of POK and AK. Notes: 1. When AM "00", the POK bits in the corresponding Password/Key Register are ignored. 2. When AM = `00' and PGO = `0' bits in the zone may not be written to `1' even when using the AK. 3. Requiring authentication automatically requires the use of secure checksums for write operations (See Encrypted Checksum (Message Authentication Code, MAC) on page 17). 5.7.1.3 ER - Encryption Required When ER = "0", the host is required to activate the encryption mode in order to read/write the corresponding user zone. No data read from or written to the zone may be transmitted in the clear. If ER = "1", the host may activate the encryption mode, but isn't specifically required to do so by the device. WLM - Write Lock Mode Asserting this bit (WLM = "0") divides the user zone into 8-byte pages. The first byte of each page becomes the Write Lock Byte and defines the locked/unlocked status for each byte in the page. Write access is forbidden to a byte if its associated bit in the Write Lock Byte is set to "0". Bit 7 controls byte 7; bit 6 controls byte 6, etc. By setting bit 0 to "0" locks the Write Lock Byte itself. Enabling Write Lock Mode limits write operations to one byte at a time. MDF - Modify Forbidden Asserting this bit (MDF = "0") renders the user zone read-only at all times. The user zone must, therefore, be programmed before setting this bit to "0". PGO - Program Only Asserting this bit (PGO = "0") allows changing of data within the user zone under protection from "1" to "0" and never from "0" to "1". Password/Key Registers Four, eight or sixteen 8-bit Password/Key registers receive definition during device personalization. Each Password/Key register works in conjunction with a corresponding Access register to define the security settings of each zone. The values programmed have an immediate affect on the logic of the device. The default value is "1" for each bit. Bit 3 is reserved and should be left as value "1." 5.7.1.4 5.7.1.5 5.7.1.6 5.7.2 21 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Figure 5-7. Bit 7 AK1 Password/Key Register Bit Map Bit 6 AK0 Bit 5 POK1 Bit 4 POK1 Bit 3 Res Bit 2 PW2 Bit 2 PW1 Bit 1 PW0 5.7.2.1 AK(1:0) - Authentication Key These bits define which of the four secret seeds G0-G3 must be used in an authentication to allow access to the user zone if authentication is selected in the corresponding access register. Each access register may point to a unique authentication secret. Or access registers for multiple zones may point to the same authentication secret. In this case authentication with a single secret seed will open several zones. POK(1:0) - Program Only Key When the user zone has the dual access mode selected (AM = "00"), these bits define which of the four secret seeds G0-G3 must be used in an authentication to allow read and program (i.e. write '0's only) access to the user zone. PW(2:0) - Password Set These bits define which of the eight password sets must be presented to allow access to the user zone when the password mode is selected. Identification Number A 56-bit number the customer defines during personalization. It is recommended that a unique identification number be assigned to each device. Cryptograms (C0 - C3) Each of these fields contains a 56-bit cryptogram for use during authentication. The internal logic modifies the cryptogram each time it successfully verifies the authentication. The customer may program an initial value for the cryptogram during personalization. It is recommended that the initial values be random numbers. Session Keys (S0 - S3) Each of these fields contains a 64-bit session key for use during encryption. The internal logic modifies the session key each time it successfully processes authentication or encryption verification. The session keys do not require initial values and does programming initial values are not necessary. Secret Seeds (G0-G3) Each of these fields contains a 64-bit secret seed that is used in conjunction with the corresponding cryptogram and session key during the authentication and encryption sequences. The customer programs the secret seeds during device personalization. Password Sets The password fields contain eight sets of two 24-bit passwords for read and write operations. The customer defines the values of these passwords during personalization. Successfully verifying the write password allows modification of the read and the write passwords of the same set. 5.7.2.2 5.7.2.3 5.7.2.4 5.7.3 5.7.4 5.7.5 5.7.6 22 5221A-CRYPT-10/08 5.7.7 Secure Code The secure code is the WRITE 7 password. Properly presenting this password grants write access to the configuration memory during personalization. Atmel defines the initial value of the secure code but the customer may change these values after successful presentation during a verify password operation for WRITE 7 password. Table 2: Factory Programmed Fields2 on page 1 shows the secure codes for various devices when they leave the Atmel factory. After blowing the PER fuse, verifying WRITE 7 password no longer grants write access to the configuration memory, and the configuration memory becomes read-only thereafter. 5.7.8 Password Attempts Counters (PAC) Each of the sixteen PAC fields contains an 8-bit attempts counter for the verify password process. Each PAC corresponds to a password. The attempts counter limits the number of incorrect consecutive presentations of the corresponding password to four, after which it locks the password from future use. The PAC will decrement ($FF, $EE, $CC, $88, $00) with each incorrect attempt to present the password. The PAC permanently locks the corresponding password once its value reaches $00. Prior to reaching $00, any correct presentation of the password resets the PAC value to $FF. Authentication Attempts Counters (AAC) Each of the four AAC fields contains an 8-bit attempt counter for the authentication process. Each AAC field corresponds to each authentication key set. The attempts counter limits the number of incorrect consecutive attempts to authenticate to for, after which it locks the authentication key set from future use. The AAC will decrement ($FF, $EE, $CC, $88, $00) with each incorrect attempt to authenticate. The AAC permanently locks the corresponding key set once its value reaches $00. Prior to reaching $00, any correct attempt to authenticate resets the AAC value to $FF. 5.7.9 5.8 Security Fuses CyptoMemory uses four fuses. The status of these fuses is given in a `fuse byte.' A value of `0' indicates that the fuse has been blown. Bits 4 to 7 of this byte are not used as Security Fuses and are reserved for Atmel use. Figure 5-8. F7 resv Device Fuses F6 resv F5 resv F4 resv F3 SEC F2 PER F1 CMA F0 FAB SEC, PER, CMA and FAB are non-volatile fuses blown at the end of various steps in the manufacturing and personalization process. Once blown, these fuses can never be reset. Atmel blows the SEC fuse to lock the lot history code before the device leaves the factory. Blowing the remainder of the fuses must follow the sequence: FAB - To lock the Answer To Reset and the Fab Code portions of the Configuration Memory. CMA - To lock the Card Manufacturer Code of the Configuration Memory. PER - To lock the remainder of the Configuration Memory. Any attempt to blow a fuse out of sequence will be unsuccessful. 8 provides a summary of access rights for all portions of the memory for each fuse condition. 23 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Table 5-5. Fuse Access Rights Summary Zone Operation SEC = 0 Read Write Read Free Write Read Write Read Write Read Write Free Secure Code Free Forbidden Free Secure Code Free Secure Code Secure Code Write Read Secure Code Write Passwords Read Secure Code Write Read Write Read Forbidden Write Read AR AR AR AR Forbidden Forbidden Forbidden Free Secure Code Secure Code Free Secure Code Secure Code Free Secure Code Write PW Free Write PW Secure Code Secure Code Forbidden Free Secure Code Free Forbidden Free Secure Code Free Secure Code Secure Code Free Forbidden Free Forbidden Free Secure Code Free Secure Code Secure Code Free Forbidden Free Forbidden Free Secure Code Free Forbidden Forbidden Free Free Free Free Secure Code FAB = 0 Free Forbidden Fuse CMA = 0 Free Forbidden PER = 0 Free Forbidden Information (Except MTZ and CMC) Memory Test Zone (MTZ) Card Manufacturer Code (CMC) Read Only (Lot History Code) Access Control Cryptography (Except Encryption Keys S) Encryption Keys (S) Secret Read Write Read Password Attempts Counters (PAC) Forbidden User Zones Notes: Write 1. AR: Access rights as defined by the Access Registers 2. PW: Password 24 5221A-CRYPT-10/08 6. Protocol Selection CryptoMemory supports two application areas with different communication protocols: a 2-wire serial communication for embedded applications and an ISO 7816 asynchronous T=0 smart card interface. The power-up sequence of CryptoMemory determines what mode it shall operate in. A brief description of each of these modes follows. 6.0.1 Synchronous Mode for Embedded Applications The 2-wire serial interface is used for fast and efficient communication with logic and controllers. The synchronous mode is the default after powering up VCC due to the internal and/or external pull-up on RST. For embedded applications using CryptoMemory in standard plastic packages RST is not bonded out and this is the only communication protocol. Power-up VCC, RST goes high also. After stable VCC, apply 5 pulses CLK-SCL CLK-SCL and I/O-SDA may then be driven. Figure 6-1. Power Up Sequence for 2-Wire Mode Vcc I/O-SDA RST CLK-SCL 1 2 3 4 5 The asynchronous mode is selected when RST is low on a rising edge of CLK. Once the asynchronous mode has been selected, it is not possible to return to the synchronous mode other than by powering the device off and on again. 6.0.2 Asynchronous Mode for Smart Card Applications The asynchronous T=0 protocol defined by ISO 7816-3 is used for compatibility with the industry's standard smart card readers. Selecting this mode requires the following power-up sequence which complies with ISO 7816-3 for a cold reset in smart card applications. Power up VCC; RST, IO-SDA and CLK-SCL are low Set I/O-SDA in receive mode Provide a clock signal to CLK-SCL RST goes high after 400 clock cycles. The device will respond with a 64-bit ATR code, including historical bytes to indicate the memory density within the CryptoMemory family. Once the asynchronous mode has been selected, it is not possible to switch to the synchronous mode without powering off the device. 25 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Figure 6-2. Power Up Sequence for Smart Card Mode Vcc I/O-SDA RST CLK-SCL Smart card applications that support the 2-Wire protocol can also use CryptoMemory in the synchronous mode. ATR 7. Synchronous Protocol Communication with the CryptoMemory using the synchronous protocol is very similar to communication with AT24Cxxx Serial EEPROM devices using a two-wire protocol (TWI). Basic command structure and timing are the same however a significant difference exists when reading the CryptoMemory device that will be described below. 7.1 Start-up Sequence When first powering up the device, 5 pulses are required on CLK-SCL for reading of internal registers. This may be accomplished by sending one full command byte to the device. The device will not respond but will then be ready to respond to the next correct command sequence. * Power-up VCC. * External pull-up resistor pulls I/O-SDA high with VCC. * After stable VCC, 5 pulses are applied to CLK-SCL. * CLK-SCL and I/O-SDA may be driven. Figure 7-1. Start-up Sequence Vcc I/O-SDA CLK-SCL 1 2 3 4 5 26 5221A-CRYPT-10/08 7.2 Command Set The command set of CryptoMemory is expanded compared to a Serial EEPROM as the functionality of CryptoMemory exceeds that of a simple memory device. Each instruction sent to the CryptoMemory must have 4 bytes: Command, Address 1, Address 2 and N. The last byte, N, defines the number of any additional data bytes to be sent or received from the CryptoMemory device. In addition, the Random Read command is available. It is the only one byte command but must be preceded by an aborted write command in order to set up the read address. Table 7-1. CryptoMemory Command Set Command Description Command $B0 $B0 $B1 $B2 $B4 $B4 $B4 $B4 $B4 $B6 $B6 $BA addr $00 $01 $03 $08 $0B $00 $01 $0X Address 1 addr addr Address 2 addr addr N N $10 N $08 Data(N) N bytes N bytes Write User Zone Normal (AT88SC0104A-AT88SC0808CA) with Anti-Tearing (all devices) Random Read Read User Zone System Write Random Read Normal Read Write Config Zone (AT88SC0104CA-AT88SC0808CA) Write Fuses Set User Zone Write Config Zone with Anti-Tearing Set User Zone with Anti-Tearing Details on command usage below addr addr fuse ID zone addr zone addr $00 $00 N N 10 $00 $00 N 08 $00 N $01 $03 3 byte password X = password set (0-7) 3 byte password X = password set (0-7) N bytes N bytes N bytes System Read Verify Password Read Config Zone Read Fuse Byte Write Password Read Password $BA $0X $00 $03 7.3 Command Format Most CryptoMemory commands have the same format as a two wire interface (TWI) write command characterized by a zero in the LSB of the first byte (device address). The only exception is the Random Read command that has a one in the LSB of the device address byte. 7.3.1 Write Command Format The host generates all command and data bytes within a write transaction and sends these to the device. The device acknowledges each byte. 27 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Figure 7-2. CryptoMemory WRITE Command S T A R WRITE T Command xxxx xxx0 Address 1 0000 0000 Address 2 0a6-- ---a0 N n7--- ---n0 Data d7--- ---d0 Data x N d7--- ---d0 S T O P A C K A C K A C K A C K A C K A C K The number of bytes CryptoMemory can write within each call of a write command is constrained by the physical page size of the EEPROM memory. The maximum number of bytes to write for each call to the WRITE command is $10. All CryptoMemory WRITE commands comply with the format for the TWI write command. 7.3.2 Read Command Format The CryptoMemory READ commands (Read User Zone, System Read and Random Read) do not comply with the format of the TWI READ command. The CryptoMemory Read User Zone and System Read commands closely resemble the TWI WRITE command format by having a zero in the LSB in the device address byte. The Random Read command closely resembles the format for the TWI READ command but requires additional steps to specify the read address. Normal Read: $B2 or $B6 (Read User Zone or System Read) The CryptoMemory Normal Read command looks like a TWI write command (LSB of the fist byte = 0) but after the 4th byte of the command the CryptoMemory device will begin to send data back on the bus. The number of bytes sent by CryptoMemory will be equal to the value of N. CryptoMemory Normal Read Command 7.3.2.1 Figure 7-3. S T A READ R T Command xxxx xxx0 Address 1 0000 0000 Address 2 0a6-- ---a0 N n7--- ---n0 d7--- ---d0 A C K d7--- ---d0 NS AT CO KP Data x N A C K A C K A C K A C K Data The response of CryptoMemory will cause contention with the host on a standard TWI bus. Typically CryptoMemory cannot be used on a standard TWI bus but requires a modified TWI protocol to account for the unique read command format. 7.3.2.2 Random Read: $B1 The Random Read command provides the host ability to sequentially clock data from the device starting from a specified address. The host needs to issue a "dummy" WRITE operation in order to specify the start address for the Random Read. The host does this by clocking in the four bytes of the WRITE command and then follows them with a START condition instead of a data byte. At this point, the device's internal logic is pointing to the address from the aborted WRITE operation. The host may then issue the Random Read command byte ($B1) to which the device will respond with the EEPROM byte at the current address location and then increment the internal address by one. The device will continue to sequentially send out bytes as long as the host 28 5221A-CRYPT-10/08 keeps acknowledging each byte with an ACK. Address "roll over" is from the last byte of the current zone to the first byte of that zone. The host terminates Random Read by issuing a NACK signal instead of an ACK. Figure 7-4. S T A R T Random Read Command N A C K WRITE Command xxxx xxx0 Address 1 0000 0000 Address 2 0a6-- ---a0 N n7--- ---n0 S T A R Random Read Command T xxxx 0001 A C K A C K d7--- ---d0 Data d7--- ---d0 Data x N N A C K S T O P A C K A C K A C K A C K CryptoMemory will NACK the N parameter of the dummy write operation if the write were issued to an illegal write location. The NACK response, however, does not affect the loading of the read address. The Random Read command works for both Configuration and User Memory. It is important to implement the CryptoMemory read commands as specified; otherwise CryptoMemory responses will cause contention on the bus with a host using standard TWI protocol. 7.4 Acknowledge Polling A STOP condition ends each command. Certain commands require an acknowledge polling sequence. Acknowledge polling consists of sending a START condition followed by the command byte and determining if the device responds with an ACK. If the device is not ready for the command it will not acknowledge and the sequence must be repeated (start condition, command byte, check for ACK). The ACK indicates the operation has completed but gives no indication of the success or failure of the command. In general, READ commands do not require ACK polling. WRITE commands require ACK polling except for encrypted write commands that must be followed by a Send Checksum command. SET commands do not require ACK polling. VERIFY commands require ACK polling with $B2 or $B6 commands. The following table lists the specific requirements for ACK polling and the maximum expected delay before the device will ACK indicating readiness for the next command. 29 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA Table 7-2. Acknowledge Polling Requirement Summary Command $B0 $B0 $B0 $B0 $B1 $B2 Write Config Zone Write Fuses Set User Zone Write Config Zone with Anti-Tearing Set User Zone with Anti-Tearing $B4 $B4 $B4 $B4 $B4 $B6 $B6 $BA $BA Addr 1 addr addr addr addr n/a addr $00 $01 $03 $08 $0B $00 $01 $0X $1X Addr 2 addr addr addr addr n/a addr addr fuse ID zone addr zone addr $00 $00 $00 N N N N N n/a N N $00 $00 N $00 N $01 $03 $03 ACK Polling CMD Required, any CMD Required, any CMD No, Send Checksum No, Send Checksum Not Required Not Required Required, any CMD Required, any CMD Not Required Required, any CMD Not Required Not Required Not Required Required; $B2 or $B6 Required; $B2 or $B6 Delay 5ms 20ms 0 0 0 0 5ms 5ms 0 20ms 0 0 0 10ms 10ms Command Description Write User Zone Normal Normal - with AntiTearing Encrypted Encrypted with Anti-Tearing Random Read Read User Zone System Write System Read Read Config Zone Read Fuse Byte Verify Password Write Password Read Password Note: Delays are based on operation at 250C 7.5 Device Addressing The first nibble of the command byte corresponds to the device address. All CryptoMemory devices will respond to the device address $B. A specific device may be set to respond to another value ($0 to $F) in addition to $B by setting this value in the second nibble of the Device Configuration Register (DCR) in the configuration memory. The DCR is set to $FF at the Atmel factory and thus will respond to device address $B and $F unless the DCR is modified. For a device to respond only to $B the DCR should be set to $B also. 7.6 Command Descriptions In the following section operations are described in two parts: the instruction is described first from a functional point of view (parameters and data exchanged), after which they are detailed for the synchronous two-wire protocol. In these diagrams, values are shown in binary format with bits to the left transmitted first, i.e. bytes are transmitted most significant bit first. 30 5221A-CRYPT-10/08 7.7 7.7.1 Write User Zone: $B0 Functional Write User Zone Command Functional Description Figure 7-5. Host Command Address 1 Address 2 Number of bytes N Data ... Data Device N data bytes The Write User Zone command $B0 allows writing of data in the device's currently selected user zone (the procedure for selecting a user zone is described below, see "System Write: $B4" ). The data byte address to be written is defined by Address 1 and Address 2 in the command. The value N defines how many bytes are to be written. The maximum number of bytes that may be written is $10 corresponding to the EEPROM page size. In anti-tearing mode the maximum value for N is $08 for all devices. A write in anti-tearing mode is activated with the Set User Zone with anti-tearing command; all subsequent write operations to the user zone will be in anti-tearing mode. A write may be started in the middle of an EEPROM page but should not extend past the end of the page. If the host is not allowed to write in the zone, the device will not acknowledge the N byte. After this command the host must perform ACK polling. Figure 7-6. Write User Zone Command Structure S T A R T Command 1011 0000 Address 1 xxxx xxxx Address 2 xxxx xxxx N xxxx xxxx Data d7--- ---d0 Data x N d7--- ---d0 S T O P A C K A C K A C K A C K A C K A C K 31 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 7.8 7.8.1 Random read: $B1 Functional Random Read Command Functional Description Figure 7-7. Host WRITE Command Address A1 Address A2 Number of bytes N RANDOM READ Device Data ... Data N data bytes The Random Read command $B1 allows reading of data from the devices configuration memory or currently selected user zone (The "System Write: $B4" section describes how to select a user zone). The Random Read command provides the host ability to sequentially clock data from the device starting from a specified address. The host needs to issue a "dummy" WRITE operation in order to specify the start address for the Random Read. The host does this by clocking in the four bytes of the WRITE command and then follows them with a START condition instead of a data byte. At this point, the device's internal logic is pointing to the address from the aborted WRITE operation. The host may then issue the Random Read command byte ($B1) to which the device will respond with the EEPROM byte at the current address location and then increment the internal address by one. The device will continue to sequentially send out bytes as long as the host keeps acknowledging each byte with an ACK. Address "roll over" is from the last byte of the current zone to the first byte of that zone. The host terminates Random Read by issuing a NACK signal instead of an ACK. Figure 7-8. S T A R T Random Read Command Structure N A C K WRITE Command xxxx xxx0 Address 1 0000 0000 Address 2 0a6-- ---a0 N n7--- ---n0 S T A R Random Read Command T xxxx 0001 A C K A C K d7--- ---d0 Data d7--- ---d0 Data x N N A C K S T O P A C K A C K A C K A C K 32 5221A-CRYPT-10/08 7.9 7.9.1 Read User Zone: $B2 Functional Figure 7-9. Read User Zone Command Functional Description Host Read Command Address 1 Address 2 Number of bytes N Device Data ... Data N data bytes The Read User Zone command $B2 allows reading of data from the device's currently selected user zone (the procedure for selecting a user zone is described below under ""). The data byte address to be read is defined by Address 1 and Address 2 in the command and is internally incremented following the transmission of each data byte. The value N defines how many bytes CryptoMemory will read, a value of zero will result in 256 bytes read. The host however may cease clocking the device and end the transmission with a NACK and STOP at anytime prior to receiving all N bytes. During a read operation the address will "roll over" from the last byte of the current zone, to the first byte of the same zone. If the host is not allowed to read the zone, the device will not acknowledge the N byte. Figure 7-10. Read User Zone Command Structure S T A R T Command 1011 0010 Address 1 xxxx xxxx Address 2 xxxx xxxx N xxxx xxxx d7--- ---d0 A C K d7--- ---d0 NS AT CO KP Data x N A C K A C K A C K A C K Data 33 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 7.10 7.10.1 System Write: $B4 Functional Figure 7-11. System Write Command Functional Description Host Command Address 1 Address 2 Number of bytes N Data ... Data Device N data bytes The System Write command allows writing of configuration data to the device. Depending on the value of the Address 1 parameter, the host may write data in the configuration zone, program the fuses, or set the user zone. Table 7-3. System Write Command Detail Command $B4 $B4 $B4 $B4 Addr 1 $00 $01 $02 $03 Addr 2 addr fuse ID $00 zone N N $10 $00 $02 $00 2 bytes Data(N) N bytes Command Description Write Config Zone Write Fuses Send Checksum Set User Zone 7.10.1.1 Write Config Zone The maximum number of bytes that may be written is $10 and this corresponds to the EEPROM page size. In anti-tearing mode the maximum value for N is $08 for all devices. A write may be started in the middle of an EEPROM page but should not extend past the end of the page. If the address provided is an unauthorized address, the device will not write the requested data. Since access rights vary throughout the configuration zone, the host may provide an authorized starting address, but a number of bytes that causes the device to reach unauthorized data. In this case, the device will prevent the internal write cycle and no bytes will be written in the EEPROM. After this command the host must perform ACK polling. Write Fuses The fuses may only be "programmed", that is written from '1' to '0'. The write fuses operation is allowed only after successfully presenting the secure code (WRITE 7 password). The fuses must be blown sequentially: FAB must be blown first, CMA may be blown only if FAB is `0', and PER only if CMA is `0'. After this command the host must perform ACK polling. The SEC fuse is blown at the Atmel factory to protect lot history information. 7.10.1.2 34 5221A-CRYPT-10/08 Table 7-4. Fuse SEC FAB CMA PER Fuse Identification Fuse ID (Addr 2) $07 $06 $04 $00 7.10.1.3 Set User Zone Before reading and writing data in the user zones, the host must select a zone with this command. At this time the host chooses whether anti-tearing should be active for this zone. Anti-Tearing Command $B4 $B4 Addr 1 $08 $0B Addr 2 addr zone N N $08 $00 Data (N) N bytes Table 7-5. Command Description Write Config Zone with Anti-Tearing Set User Zone with Anti-Tearing Data written to the configuration zone may be done with anti-tearing enabled by setting address 1 to $08 of the write configuration zone command. To enable anti-tearing for writes to a user zone a set user zone command is executed with address 1 set to $0B. All subsequent write user zone commands will be executed with anti-tearing enabled until the next set user zone command. Anti-tearing should be turned off if not required, as it would otherwise cause more write cycles than necessary. Figure 7-12. System Write Command Detail S T A R T Command 1011 0100 Address 1 0000 xxxx Address 2 xxxx xxxx N xxxx xxxx Data d7--- ---d0 Data x N d7--- ---d0 S T O P A C K A C K A C K A C K A C K A C K 35 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 7.11 7.11.1 System Read: $B6 Functional Figure 7-13. System Read Command Functional Description Host Read Command Address 1 Address 2 Number of bytes N Device Data ... Data N data bytes The System Read command allows reading of system data from the device. Depending on the value of address 1, the host may read the data in the configuration zone, or the fuses. Table 7-6. Zone Configuration Example Command $B6 $B6 Addr 1 $00 $01 Addr 2 addr $00 N N $01 Command Description Read Config Zone Read Fuse Byte 7.11.2 Read Config Zone The data byte address to be read is defined by address 2 in the command and is internally incremented following the transmission of each data byte. The value N defines how many bytes CryptoMemory will read, a value of zero will result in 256 bytes read. If the address provided is an unauthorized address, the device will not ACK the N byte and will not return any data. Since access rights vary throughout the configuration zone, the host may provide an authorized starting address and a number of bytes N that causes the device to reach unauthorized data. In this case the device will transmit the fuse byte (see below) in place of unauthorized bytes. 7.11.3 Read Fuse Byte Fuse data is returned in the form of a single byte. Bits 0 to 3 represent the fuse states, a value of `0' indicates the fuse has been blown. Bits 4 to 7 are not used as security fuses and are reserved by Atmel. Fuse Byte Bit-Map F6 resv F5 resv F4 resv F3 SEC F2 PER F1 CMA F0 FAB Table 7-7. F7 resv 36 5221A-CRYPT-10/08 7.12 7.12.1 Verify Password: $BA Functional Figure 7-14. Verify Password Command Functional Description Host Command Password Index PW1 PW2 PW3 Device 3 password bytes READ password indices: $10 to $17 for passwords 0,1,2 & 7. WRITE password indices: $00 to $07 for passwords 0,1,2 & 7. Secure code index: $07 (equivalent to WRITE Password 7). Four password index bits "r" and "ppp" indicate the password to compare: r = 0 : WRITE password, r = 1 : READ password, p2p1p0: Password set number. Figure 7-15. Verify Password Command Structure S T A R T Command 1011 1010 PW Index 000r 0p2p1p0 Parameter 2 **** **** N=3 0000 0011 Data x 3 d7--- ---d0 S T O P A C K A C K A C K A C K A C K Once the sequence has been carried out, the device requires the host to perform an ACK polling sequence with the system read command $B6. In order to know whether the inserted password was correct, the host can read the corresponding attempts counter and verify the value is zero. 37 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 8. Initialization Example The first step in initializing CryptoMemory is to determine what data is to be stored in the device and what the security settings need to be to protect this data. Once defined, determine the proper settings for CryptoMemory registers and select values for passwords. To initialize the CryptoMemory device, the following sequence is recommended to take place in a secure location to protect sensitive data and passwords that may be loaded into the device. 8.1 Write Data to User Zones In the default configuration from Atmel, all user zones have free access rights. Writing initial data into the user zones should be done before setting security configurations. Use the Set User Zone command and Write User Zone command to write initial data into the user zones. The Read User Zone command may be used to verify the data written. 8.2 Unlock Configuration Zone Before any data can be written to the configuration zone, it must be unlocked by presenting the correct security code (WRITE 7 Password). Use the Verify Password command with the proper secure code supplied by Atmel to unlock the configuration zone. Use the Read Config Zone command to read back the security code at address $E9 for verification that the configuration zone has been unlocked. 8.3 Write Data to Configuration Zone Writing this data is accomplished by performing the Write Config Zone command at the appropriate address location. The Read Config Zone command may be used to verify the data written. As soon as values are written to the registers, keys, and passwords, they become effective in determining the security of the user zones. 8.4 Set Security Fuses Once all data is written and verified into user zones and the configuration zone the security fuses should be set before the device is released from the secure location used for device initialization. There are three fuses, FAB, CMA and PER that must be set. These three fuses must be set in the order listed (FAB, then CMA, then PER). The Write Fuse command is used to set each of the three fuses individually. The Read Fuse command may be used to check the status of all three fuses. Once all fuses have been set the Read Fuse command should return a value of zero for the second nibble of the fuse byte. The AT88SC0104CA is used for this example. A small pattern is written into the first two user zones. Security for each of these two user zones and the associated register values are shown in the table below. Simple values for passwords are used. Table 8-1. User Zone 0 1 CryptoMemory Asynchronous Command Set Data Zone 0 Data Zone 1 Data Security Requirements None Read/Write Password (Set 1) Access Register $FF $7F Password/Key Register $FF $F9 38 5221A-CRYPT-10/08 The following shows the two-wire commands sent to the CryptoMemory device for the purpose of initializing the device. The flow is consistent with the steps described above; comments have been added as indicated with an asterisk (*). *AT88SC0104CA Initialization Example *WRITE DATA TO USER ZONES *Set User Zone 0 B4 03 00 00 *Write data = Zone 0 Data B0 00 00 0B 5A 6F 6E 65 20 30 20 44 61 74 61 *Set User Zone 1 B4 03 01 00 *Write data = Zone 1 Data B0 00 00 0B 5A 6F 6E 65 20 31 20 44 61 74 61 *UNLOCK CONFIGURATION ZONE BA 07 00 03 DD 42 97 *WRITE CODES IN CONFIGURATION ZONE *Write Card Mfg Code = P001 B4 00 0B 04 50 30 30 31 *Write Identification Number = 00000000012345 B4 00 19 07 00 00 00 00 01 23 45 *Write Issuer Code = STATION 035 B4 00 40 10 53 54 41 54 49 4F 4E 20 30 33 35 00 00 00 00 00 *WRITE REGISTERS IN CONFIGURATION ZONE *Write Registers AR1/PR1 = 7F F9 B4 00 22 02 7F F9 DF BF 57 B9 *WRITE PASSWORDS IN CONFIGURATION ZONE *Write Passwords, read 7 = 10 00 01, write 7 = 11 00 11 B4 00 B9 07 11 00 11 FF 10 00 01 *READ ENTIRE CONFIGURATION ZONE TO VERIFY B6 00 00 F0 *Device Response: 3B B2 11 00 10 80 00 01 10 10 FF 50 30 30 31 FF 8C AD A8 10 0A AB FF FF FB 00 00 00 00 01 23 45 39 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA FF FF 7F F9 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 53 54 41 54 49 4F 4E 20 30 33 35 00 00 00 00 00 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 11 00 11 FF 10 00 01 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF *SET SECURITY FUSES *Set FAB Fuse B4 01 06 00 *Set CMA Fuse B4 01 04 00 *Set PER Fuse B4 01 00 00 *Read Fuse Byte = X0 B6 01 00 01 *Device Response: 00 40 5221A-CRYPT-10/08 9. Asynchronous T=0 Protocol 9.1 Character format The CryptoMemory complies with the asynchronous T=0 protocol defined in ISO 7816-3. The character format is shown in the following figure: note that the byte is transmitted with the least significant bit first. 8 data bits Z I/O A 0 t1 (n 0,2) etu Even parity is used: the parity bit is such that the overall sum of bits in the data byte and the parity bit is an even number. If a transmission error is detected, the receiving device indicates this by applying a low level on the I/O channel during the guard time. This tells the transmitting device to retransmit the byte. Start bit d0 d1 d2 d3 d4 d5 d6 d7 Parity bit p Next Start bit Guard Time tn t 10 9.2 Command format The command sequence is as follows: 1. In compliance with ISO 7816-3, the host must send the header consisting of 5 characters: CLA, INS, P1, P2, P3. a. CLA refers to a class of instructions. This byte isn't tested by the device. b. c. INS is the instruction byte. P1 and P2 are reference bytes, such as a data byte address or password index. d. P3 is the number of data bytes transferred during the command. For outgoing transfers (e.g. read commands), P3 = 0 means that 256 data bytes will be emitted by the card. For incoming commands, P3 = 0 means that no data bytes will be transferred. 2. The device replies with a "procedure byte", normally equal to the INS code received. If a problem occurred, then the device will respond with a status word pair SW1-SW2, indicating the end of the command. 3. Data transfer (P3 bytes). 4. A final SW1-SW2 sequence gives the status of the device after completion of the command. A normal completion is indicated by SW1-SW2 = $90-$00. Note: for all bytes transmitted by the device or by the host, including header, procedure, status and data bytes, if a parity error is detected, the receiver requests that byte to be sent again (see character format). 41 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 9.2.1 PPS Support All CryptoMemory devices with user memory sizes 32Kbits and larger support the Protocol and Parameter Selection (PPS) protocol, section 7 of ISO 7816-3. The AT88SCxxxxCA family of devices only has up to 8Kbits of user memory. Please consult the respective specification for any of our higher density devices in the AT88SCxxxxC family for information on PPS support. 9.3 Command Set CryptoMemory Asynchronous Command Set Command Descriptions CLA $00 $00 $00 $00 $00 $00 $00 $00 $00 $00 $00 $00 $00 $00 INS $B0 $B0 $B2 $B4 $B4 $B4 $B4 $B4 $B4 $B6 $B6 $B6 $BA $BA P1 addr addr addr $00 $01 $02 $03 $08 $0B $00 $01 $02 $0X $1X P2 addr addr addr addr fuse ID $00 zone addr zone addr $00 $00 $00 $00 P3 N $10 N $08 N N $10 $00 $02 $00 N $08 $00 N $01 $02 $03 $03 3 byte password X = password set (0, 1,2 or 7) 3 byte password X = password set (0, 1,2 or 7) N bytes N bytes 2 bytes Data (N) N bytes N bytes Table 9-1. B0 Write User Zone Normal with Anti-Tearing B2 B4 Read User Zone System Write Read User Zone Write Config Zone Write Fuses Send Checksum Set User Zone Write Config Zone w/a-t Set User Zone w/a-t B6 System Read Read Config Zone Read Fuse Byte Read Checksum BA Verify Password Write Password Read Password 9.3.1 Status Words Table 9-2. SW1 SW2 $62 $00 $67 $00 $69 $00 $6B $00 $6D $00 $90 $00 Asynchronous Mode Return Status Words Definitions Meaning The memory is unchanged, waiting for checksum The length is incorrect The command is unauthorized The address is incorrect The instruction code is invalid The command was successfully executed 42 5221A-CRYPT-10/08 These status words indicate the state of the device at the end of the command. In normal conditions, the device sends the INS byte as the procedure byte, and $90 $00 as the final status word. In certain conditions described below, the device may interrupt the command by returning a status word in place of INS as the procedure byte. $67 $00 is returned as a procedure byte when the number of data bytes to be transferred is incorrect. $69 $00 is returned after read/write commands as procedure bytes if the host is not allowed to read/write at the address provided. It is also returned after Password commands if the maximum number of attempts has been exceeded. The device will return $69 $00 as a final status word in place of $90 $00, if the password presentation failed. $6B $00 is returned as procedure bytes if the address is incorrect. $6D $00 is returned as procedure bytes if the INS code received is not supported. 9.3.2 Example: Write EEPROM command The following illustrates the data exchanges that occur during a write operation of 4 bytes: $04, $09, $19, $97 to addresses $02, $03, $04, $05 in the current user zone. Host Start CLA INS P1 P2 P3 Device Val ** $B0 ** $02 $04 Note Class (ignored by CryptoMemory) Write instruction Address byte A1 (ignored by 0104CA - 0808CA) Address byte A2 = $02 4 data bytes Device responds with INS code Byte to be written at start address $02. Byte to be written at address $03 Byte to be written at address $04 Byte to be written at address $05 ~ 5 ms Write operation successful INS Data Data Data Data Write Cycle SW1 Finish SW2 $B0 $04 $09 $19 $97 $90 $00 43 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 9.4 9.4.1 9.4.1.1 Command Descriptions Write User Zone: $B0 Functional Figure 9-1. Write User Zone Functional Command Description Host Command Address A1 Address A2 Number of bytes N Data ... Data Device N data bytes The Write User Zone command $B0 allows writing of data into the device's currently selected user zone (the procedure for selecting a user zone is described below, (see ""). The maximum number of bytes that may be written in a single WRITE operation is $10 and corresponds to the EEPROM page size. Each data byte within a page must only be loaded once. In anti-tearing mode the maximum value for N is $08 for all devices. A write in anti-tearing mode is activated with the Set User Zone command with the anti-tearing option (00 B4 0B zz 00), all subsequent writes to the user zone will be in anti-tearing mode. If the host is not allowed to write in the zone, the device will return the "Command Unauthorized" code ($69 $00) after it has received the P3 byte. Figure 9-2. Write User Zone Command Structure Command Header CLA ** INS : Command P1 : Address 1 P2 : Address 2 P3 : N 0a6-- ---a0 000n4 ---n0 $B0 0000 0000 Data(1) d7--- ---d0 Data Sent ... ... Data(N) d7--- ---d0 44 5221A-CRYPT-10/08 9.4.2 9.4.2.1 Read User Zone: $B2 Functional Figure 9-3. Read User Zone Command Functional Description Host Read Command Address 1 Address 2 Number of bytes N Device Data ... Data N data bytes The Read User Zone command $B2 allows reading of data from the device's currently selected user zone (the procedure for selecting a user zone is described below under ""). The byte address is internally incremented following the transmission of each data byte. During a read operation the address will "roll over" from the last byte of the current zone, to the first byte of the same zone. If the host is not allowed to read the zone, the device will return the "Command Unauthorized" code ($69 $00) after it has received the header. Figure 9-4. Read User Zone Command Structure Command Header CLA ** INS : Command P1 : Address 1 P2 : Address 2 0a6-- ---a0 $B2 0000 0000 P3 : N n7--- ---n0 Data Returned Data(1) d7--- ---d0 ... ... Data(N) d7--- ---d0 45 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 9.4.3 9.4.3.1 System WRITE: $B4 Functional Figure 9-5. System Write Command Functional Description Host Command Parameter P1 Parameter P2 Number of bytes N Data ... Data Device N data bytes The System Write command allows writing of system data to the device. Depending on the value of the P1 parameter, the host may write data in the configuration zone program the fuses or set the user zone. Table 9-3. Command Write Config Zone Write Fuses Send Checksum Set User Zone System Write Command Detail CLA $00 $00 $00 $00 INS $B4 $B4 $B4 $B4 P1 $00 $01 $02 $03 P2 addr fuse ID $00 zone P3 N $10 $00 $02 $00 2 bytes Data (N) N bytes The anti-tearing function is controlled by P1: the host may choose to write in the configuration zone with anti-tearing enabled by setting P1 = $08 instead of $00. Similarly, the host may choose to activate anti-tearing for a user zone by carrying out the Set User Zone command with P1 = $0B instead of $03. All subsequent Write User Zone commands are then carried out with anti-tearing enabled until the next Set User Zone command. Anti-tearing should be turned off if not required, as it would otherwise cause more write cycles than necessary. 46 5221A-CRYPT-10/08 Table 9-4. Command System Write with Anti-Tearing CLA $00 $00 INS $B4 $B4 P1 $08 $0B P2 addr zone P3 N $08 $00 Data (N) N bytes Write Config Zone w/a-t Set User Zone w/a-t 9.4.4 Write Config Zone The maximum number of bytes to write for each call of the WRITE command is $16 and corresponds to the EEPROM page size. Each data byte within a page must only be loaded once. In anti-tearing mode the maximum value for N is $08 for all devices. If the address provided at P2 is an unauthorized address, the device will return the "Command Unauthorized" code ($69 $00) after it has received the header. Since access rights vary throughout the configuration zone, the host may provide an authorized starting address, but a number of bytes that causes the device to reach unauthorized data. In this case, the device will prevent the internal write cycle and no bytes will be written in the EEPROM. At the end of the command the "Command Unauthorized" code ($69 $00) will be returned instead of $90 $00 to indicate that no write cycle occurred. 9.4.5 Write Fuses Table 9-5. Fuse SEC FAB CMA PER Fuse Bytes Fuse ID (P2) $07 $06 $04 $00 The fuses may only be "programmed", that is written from '1' to '0'. The write fuses operation is only allowed after successfully presenting the secure code (WRITE 7 password). The fuses must be blown sequentially: FAB must be blown first, CMA may be blown only if FAB is `0', and PER only if CMA is `0'. The SEC fuse is blown at the Atmel factory to protect lot history information. 9.4.6 Set User Zone Before reading and writing data in the user zones, the host should select a zone with this command. At this time the host may choose whether anti-tearing should be active for this zone. Figure 9-6. System Write Command Structure Command Header CLA ** INS : Command $B4 P1 p7--- ---p0 P2 p7--- ---p0 P3 n7--- ---n0 Data(1) d7--- ---d0 Data Sent ... ... Data(N) d7--- ---d0 47 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 9.5 9.5.1 System READ: $B6 Functional System Read Command Functional Description Host Read Command Address 1 Address 2 Number of bytes N Device Data ... Data N data bytes The System Read command allows reading of system data from the device. Depending on the value of the P1 parameter, the host may read the data in the configuration zone, or the fuses. Table 9-6. Command Read Config Zone Read Fuse Byte System Read Command Detail CLA $00 $00 INS $B6 $B6 P1 $00 $01 P2 addr $00 P3 N $01 Data (N) 9.5.2 Read Config Zone To read 256 bytes, the host should set N = $00. This is true for any outgoing command, and is defined by ISO 7816-3. If the address provided at P2 is an unauthorized address, the device will return the "Command Unauthorized" code ($69 $00) after it has received the header. Since access rights vary throughout the configuration zone, the host may provide an authorized starting address, but a number of bytes N that causes the device to reach unauthorized data. In this case, the device will transmit the authorized bytes, but unauthorized bytes will be replaced by the "fuse byte" (see below). At the end of this command the "Command Unauthorized" code ($69 $00) will be returned instead of $90 $00 to indicate that some of the bytes returned are not valid. Read Fuse Byte Fuse data is returned in the form of a single byte. Bits 0 to 3 represent the fuse states; a value of `0' indicates the fuse has been blown. Bits 4 to 7 are not used as Security Fuses and are reserved by Atmel. Figure 9-7. F7 resv 9.5.3 Fuse Byte Bit-Map F6 resv F5 resv F4 resv F3 SEC F2 PER F1 CMA F0 FAB Figure 9-8. System Read Command Structure Command Header CLA ** INS : Command $B6 P1 p7--- ---p0 P2 p7--- ---p0 P3 n7--- ---n0 Data Returned Data(1) d7--- ---d0 ... ... Data(N) d7--- ---d0 48 5221A-CRYPT-10/08 9.5.4 9.5.4.1 Verify Password: $BA Functional Figure 9-9. Verify Password Command Functional Description Host Command Password Index PW1 PW2 PW3 Device 3 password bytes Read password indices : $10 to $17 for passwords 0,1,2 & 7. Write password indices : $00 to $07 for passwords 0,1,2 & 7. Secure code index : $07 (equivalent to WRITE Password 7). Four password index bits "r" and "ppp" indicate the password to compare: r = 0: WRITE password, r = 1: READ password, p2p1p0: Password set number. Figure 9-10. Verify Password Command Structure Command Header CLA ** INS : Command P1 : PW Index $BA 000r 0p 2p1p0 P2 ** P3 $03 Data Sent PW1 PW2 PW3 d7--- ---d0 d15 -- ---d8 d23-- --d16 If the maximum number of trials has been exceeded, the device will return $69 $00 instead of the INS code, after receiving the header, to indicate the command is unauthorized. The device increments the associated attempts count before verifying the password, to prevent attacks. If the password is correct, the device memorizes this success, clears the attempts count and returns $90 $00. If the password is wrong, the device simply returns $69 $00 after incrementing the attempts count. The WRITE 7 password is also known as the Secure Code and must be properly presented before access to the configuration zone is granted when personalizing the device. 49 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 10. Initialization Example The first step in initializing CryptoMemory is to determine what data is to be stored in the device and what the security settings need to be to protect this data. Once defined, determine the proper settings for CryptoMemory registers and select values for passwords. To initialize the CryptoMemory device, the following sequence is recommended to take place in a secure location to protect sensitive data and passwords that may be loaded into the device. 10.1 Write Data to User Zones In the default configuration from Atmel, all user zones have free access rights. Writing initial data into the user zones should be done before setting security configurations. Use the Set User Zone command and Write User Zone command to write initial data into the user zones. The Read User Zone command may be used to verify the data written. 10.2 Unlock Configuration Zone Before any data can be written to the configuration zone, it must be unlocked by presenting the correct security code (Write 7 Password). Use the Verify Password command with the proper secure code supplied by Atmel to unlock the configuration zone. Use the Read Config Zone command to read back the security code at address $E9 for verification that the configuration zone has been unlocked. 10.3 Write Data to Configuration Zone Writing this data is accomplished by performing the Write Config Zone command at the appropriate address location. The Read Config Zone command may be used to verify the data written. As soon as values are written to the registers, keys, and passwords, they become effective in determining the security of the user zones. 10.4 Set Security Fuses Once all data is written and verified into user zones and the configuration zone the security fuses should be set before the device is released from the secure location used for device initialization. There are three fuses, FAB, CMA and PER that must be set. These three fuses must be set in the order listed (FAB, then CMA, then PER). The Write Fuse command is used to set each of the three fuses individually. The Read Fuse command may be used to check the status of all three fuses. Once all fuses have been set the Read Fuse command should return a value of zero for the second nibble of the fuse byte. The AT88SC0104CA is used for this example. A small pattern is written into the first two user zones. Security for each of these two user zones and the associated register values are shown in the table below. Simple values for passwords are used. 50 5221A-CRYPT-10/08 Table 10-1. User Zone 0 1 2 Zone Configuration Example Data Zone 0 Data Zone 1 Data Zone 2 Data Security Requirements None Read/Write Password (Set 1) Read/Write Authentication (Set 2) Read/Write Password (Set 1), Read/Write Authentication (Set 1) with Encryption Required Access Register $FF $7F $DF Password/Key Register $FF $F9 $BF 3 Zone 3 Data $57 $B9 The following shows the two-wire commands sent to the CryptoMemory device for the purpose of initializing the device. The flow is consistent with the steps described above; comments have been added as indicated with an asterisk (*). *AT88SC0104CA Initialization Example *WRITE DATA TO USER ZONES *Set User Zone 0 00 B4 03 00 00 *Write data = Zone 0 Data 00 B0 00 00 0B 5A 6F 6E 65 20 30 20 44 61 74 61 *Set User Zone 1 00 B4 03 01 00 *Write data = Zone 1 Data 00 B0 00 00 0B 5A 6F 6E 65 20 31 20 44 61 74 61 *UNLOCK CONFIGURATION ZONE 00 BA 07 00 03 DD 42 97 *WRITE CODES IN CONFIGURATION ZONE *Write Card Mfg Code = P001 00 B4 00 0B 04 50 30 30 31 *Write Identification Number = 00000000012345 00 B4 00 19 07 00 00 00 00 01 23 45 *Write Issuer Code = STATION 035 00 B4 00 40 10 53 54 41 54 49 4F 4E 20 30 33 35 00 00 00 00 00 *WRITE REGISTERS IN CONFIGURATION ZONE *Write Registers AR1/PR1 = 7F F9 51 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 00 B4 00 22 02 7F F9 DF BF 57 B9 *WRITE PASSWORDS IN CONFIGURATION ZONE *Write Passwords, read 7 = 10 00 01, write 7 = 11 00 11 00 B4 00 B9 07 11 00 11 FF 10 00 01 *READ ENTIRE CONFIGURATION ZONE TO VERIFY 00 B6 00 00 F0 *Device Response: 3B B2 11 00 10 80 00 01 10 10 FF 50 30 30 31 FF 8C AD A8 10 0A AB FF FF FB 00 00 00 00 01 23 45 FF FF 7F F9 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 53 54 41 54 49 4F 4E 20 30 33 35 00 00 00 00 00 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 11 00 11 FF 10 00 01 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF *SET SECURITY FUSES *Set FAB Fuse 00 B4 01 06 00 *Set CMA Fuse 00 B4 01 04 00 *Set PER Fuse 00 B4 01 00 00 *Read Fuse Byte = X0 00 B6 01 00 01 *Device Response: 00 52 5221A-CRYPT-10/08 11. Absolute Maximum Ratings Stresses beyond those listed under `Absolute Maximum Ratings' may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this specification are not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect device reliability. Absolute Maximum Ratings Operating Temperature Storage Temperature Voltage on Any Pin with Respect to Ground Maximum Operating Voltage DC Output Current -40 C to +85 C -65 C to + 150 C -0.7 to VCC + 0.7V 6.0V 5.0mA 53 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 11.1 DC and AC Characteristics DC Characteristics Parameter Supply Voltage Supply Current (VCC = 3.3V) Supply Current (VCC = 3.3V) Supply Current (VCC = 3.3V) Supply Current (VCC = 3.3V) Standby Current (VCC = 3.3V) SDA/IO Input Low Voltage CLK Input Low Voltage RST Input Low Voltage SDA/IO Input High Voltage SCL/CLK Input High Voltage RST Input High Voltage SDA/IO Input Low Current SCL/CLK Input Low Current RST Input Low Current SDA/IO Input High Current SCL/CLK Input High Current RST Input High Current SDA/IO Output High Voltage SDA/IO Output Low Voltage SDA/IO Output High Current SDA/IO Output Low Current 0< VIL < VCC x 0.15 0< VIL < VCC x 0.15 0< VIL < VCC x 0.15 VCC x 0.7 < VIH < VCC VCC x 0.7 < VIH < VCC VCC x 0.7 < VIH < VCC 20K external pull-up IOL = 1mA VOH VOL VCC x 0.7 0 Async READ at 3.57MHZ Async WRITE at 3.57MHZ Sync READ at 1MHZ Sync WRITE at 1MHZ VIN = VCC or GND 0 0 0 VCC x 0.7 VCC x 0.7 VCC x 0.7 Test Condition Min 2.7 Typ Max 3.6 5 5 5 5 100 VCC x 0.2 VCC x 0.2 VCC x 0.2 VCC VCC VCC 15 15 50 20 100 150 VCC VCC x 0.15 20 10 Units V mA mA mA mA A V V V V V V A A A A A A V V A mA Table 11-1. Symbol VCC ICC ICC ICC ICC ISB VIL VIL VIL VIH VIH VIH IIL IIL IIL IIH IIH IIH VOH VOL IOH IOL Notes: 1. Applicable over recommended operating voltage range from VCC = 2.7V to 3.6V 2. TAC = -400C to +850C (unless otherwise noted) 54 5221A-CRYPT-10/08 Table 11-2. Symbol FCLK FCLK AC Characteristics Parameter Async Clock Frequency Sync Clock Frequency Clock Duty Cycle Min 1 0 40 Max 4 1 60 1 1 9% x period 9% x period 250 200 200 10 100 200 20 5 Units MHZ MHZ % S S S S nS nS nS nS nS nS nS mS TR TF TR TF TAA THD.STA TSU.STA THD.DAT TSU.DAT TSU.STO TDH TWR Notes: Rise Time - SDA/IO, RST Fall Time - SDA/IO, RST Rise Time - SCL/CLK Fall Time - SCL/CLK Clock Low to Data Out Valid Start Hold Time Start Set-up Time Data In Hold Time Data In Set-up Time Stop Set-up Time Data Out Hold Time Write Cycle Time 1. Applicable over recommended operating range from VCC = 2.7V to 3.6V 2. TAC = -400C to +850C, CL = 30pF (unless otherwise noted) 11.2 11.2.1 Timing Diagrams for Synchronous Communications Bus Timing: Figure 11-1. SCL: Serial Clock, SDA: Serial Data I/O tF tLOW tHIGH tR tLOW SCL tSU.STA tHD.STA tHD.DAT tSU.DAT tSU.STO SDA IN tAA tDH SDA OUT 55 AT88SCXXXXCA 5221A-CRYPT-10/08 AT88SCXXXXCA 11.2.2 Write Cycle Timing: Figure 11-2. SCL: Serial Clock, SDA: Serial Data I/O SCL SDA 8th BIT WORDn ACK twr STOP CONDITION Note: (1) START CONDITION The write cycle time tWR is the time from a valid stop condition of a write sequence to the end of the internal clear/write cycle. Figure 11-3. Data Validity DATA CHANGE ALLOWED Figure 11-4. Start and Stop Definition 56 5221A-CRYPT-10/08 Figure 11-5. Output Acknowledge 12. Tamper Detection CryptoMemory contains tamper detection sensors to detect operation outside of specified limits. These sensors monitor the internal supply voltage and clock frequency. An additional sensor detects high intensity light attacks. The die is disabled and will not function when tampering is detected. 57 AT88SCXXXXCA 5221A-CRYPT-10/08 Headquarters Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131 USA Tel: 1(408) 441-0311 Fax: 1(408) 487-2600 International Atmel Asia Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimshatsui East Kowloon Hong Kong Tel: (852) 2721-9778 Fax: (852) 2722-1369 Atmel Europe Le Krebs 8, Rue Jean-Pierre Timbaud BP 309 78054 Saint-Quentin-enYvelines Cedex France Tel: (33) 1-30-60-70-00 Fax: (33) 1-30-60-71-11 Atmel Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan Tel: (81) 3-3523-3551 Fax: (81) 3-3523-7581 Product Contact Web Site www.atmel.com Technical Support cryptomemory@atmel.com Sales Contact www.atmel.com/contacts Literature Requests www.atmel.com/literature Disclaimer: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN ATMEL'S TERMS AND CONDITIONS OF SALE LOCATED ON ATMEL'S WEB SITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF PROFITS, BUSINESS INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. Atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and product descriptions at any time without notice. Atmel does not make any commitment to update the information contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel's products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life. (c) 2008 Atmel Corporation. All rights reserved. Atmel(R), Atmel logo, CryptoMemory (R), and combinations thereof, and others are registered trademarks or trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be trademarks of others. 5221A-CRYPT-10/08 |
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