Atmel's Plug & Play Host-side Cryptographic Authentication IC

The AT88SA10HS host device off-loads key storage and the execution of authentication algorithms from the system MCU, making it ideal in applications with limited microprocessor and/or memory resources, or when reduced system cost and/or complexity is desired. Until now, the host-side of the authentication process has been implemented in code executed by the system microcontroller. This code could be vulnerable to modification or copying when stored in an external unprotected flash memory device. Atmel’s CryptoAuthentication host IC enables a cost effective system solution which includes secret key storage in a special purpose highly secure hardware device. The AT88SA10HS CryptoAuthentication host device is a single-chip authentication host with a 48-bit guaranteed unique serial number, SHA-256 engine, and a 256-bit host key that is inaccessible and unreadable. The AT88SA10HS host device executes all host-side operations including challenge/response (authentication) validation and firmware integrity verification.

Atmel’s AT88SA1xxS devices are the industry’s most secure authentication ICs, with an embedded SHA-256 engine and 256-bit cryptographic key. The 256-bit length of the CryptoAuthentication key allows more possible combinations than there are atoms in the sun, making it impossible to crack using brute force methods. In contrast, the nearest competing authentication IC has a key size of only half the bits.

The AT88SA10HS includes 63 one-time, user-programmable fuses that are used to store a secret personalization value and 23 fuses that can be used for status or model number information. Once burned, there is no way to reset the value of a fuse. Additional non-burnable fuses contain the manufacturing ID and a guaranteed unique 48-bit serial number, initialized by Atmel.

Authentication. Authentication is based on a “challenge/response” protocol which uses the microprocessor host to establish communication and provide a challenge to the CryptoAuthentication on the client. The response is used to determine if the client is authentic at which point the microcontroller can decide how to utilize the client or provide a failure indication to the user. The host could be a portable power tool, printer, medical test equipment, or any device with replaceable, consumable or updateable components. The corresponding client could be the battery used in the power tool, an ink cartridge, or a medical consumable,

Verifying software. Verifying that software or other documents (modules) have not been tampered with or modified is a very important function that can be done using the CryptoAuthentication Host device. The system’s AVR or ARM microcontroller executes a hash on the contents of the module using a software SHA engine and sends the resulting digest to the CryptoAuthentication host device along with the stored ‘signature’ (hash) of the module. The CryptoAuthentication host device then calculates the expected signature for the module based on the input hash digest and its securely stored key. The integrity of the module is assured if the computation result matches the signature stored along with the module.

Physical Protection of Keys. The AT88SA10HS host-side CryptoAuthentication IC incorporates a number of physical security features designed to protect the keys. These include an active shield over the entire surface of the part, internal memory encryption, internal clock generation, glitch protection, voltage tamper detection and other physical design features. Pre-programmed keys stored on the AT88SA10HS are encrypted in such a way as to make retrieval of their values via outside analysis virtually impossible. Both the clock and logic supply voltage are internally generated, preventing any direct attack via the pins on these two signals.

Ultra-low Power Consumption. Authentication ICs spend about 1/1000 of a percent of their time active, so sleep mode power consumption is the most important power consumption metric. With a sleep mode power consumption of less than 100 nanoamps (nA), Atmel’s AT88SA10HS CryptoAuthentication host IC has virtually no effect on system battery life. The normal leakage current of the battery is substantially greater. Supply voltage for the AT88SA is 2.5V to 5.5V.