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 with Message Authentication Code (MAC) and
   Hash-Based Message Authentication Code (HMAC) options
● 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)
● 4.5Kb 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 to 5.5V supply voltage range
● 1.8V to 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