The Atmel ATSHA204 is an optimized authentication chip that includes a 4.5K-bit EEPROM. This array can be used for storage of keys, miscellaneous read/write, read-only, password or secret data, and consumption tracking. Access to the various sections of memory can be restricted in a variety of ways and then the configuration locked to prevent changes.

The chip features a wide array of defensive mechanisms specifically designed to prevent physical attacks on the chip itself or logical attacks on the data transmitted between the chip and the system.

Each ATSHA204 ships with a guaranteed unique 72-bit serial number. Using the cryptographic protocols supported by the chip, a host system or remote server can prove that the serial number is both authentic and not a copy. The ATSHA204 can generate high-quality random numbers and employ them for any purpose, including usage as part of the crypto protocols of this chip.

Access to the chip is through a standard I2C interface at speeds up to 1Mbit/sec. The chip also supports a single-wire interface that can reduce the number of GPIOs required on the system processor and/or reduce the number of pins on connectors. It is compatible with most UART or serial IO controllers. System integration is eased with a wide supply voltage range and an ultra-low sleep current of <100nA.