Introduction
The following sections introduce the features and functions of the Atmel® ATSHA204 authentication device.

FEATUREs
• Secure authentication and validation device
• Integrated capability for both host and client operations
• Superior SHA-256 hash algorithm, HMAC option
• Best-in-class, 256-bit key length; storage for up to 16 keys
• Guaranteed unique 72-bit serial number
• Internal, high-quality Random Number Generator (RNG)
• 4.5-Kbit EEPROM for keys and data
• 512 OTP (One Time Programmable) bits for fixed information
• Multiple I/O options
   • High-speed, single-wire interface
   • 1MHz I2C interface
• 2.0V – 5.5V supply voltage range
• 1.8V – 5.5V communications
• <150nA sleep current
• Extended, multi-level hardware security
• 8-lead SOIC, 8-lead TSSOP, 3-lead SOT23, 8-pad UDFN, and
   3-lead Contact packages

APPLICATIONs
• Anti-clone protection for accessories, daughter cards, and consumables
• Secure boot validation, software anti-piracy
• Network and computer access control
• Key exchange for encrypted downloads
• Authenticated/encrypted communications for control networks