Both ATSHA204 and ATECC108 are authentication devices. Authentication is the process of guaranteeing the identity of communicating parties and ensuring data integrity. Each chip uses a different approach to authentication. The ATECC108 device uses elliptical curve cryptography to provide the Elliptical Curve Digital Signature Algorithm (ECDSA). The ATSHA024 device uses a hash algorithm, SHA-256, to provide Hash Based Message Authentication Codes (HMAC).