The invention discloses an identity authentication system based on an elliptic curve. A public key and private key pair, a DH cipher code exchange protocol and hashing functions preset in equipment are used for realizing fast identity authentication, thus preventing the identity authentication by using complicated arithmetic in a public key certificate system, such as a certificate chain and digital signature. The public and private key pair of equipment A are x and xG, and the public and private key pair of equipment B are y and yG; when carrying out the identity authentication, the equipment A and the equipment B exchange x and y (or xG and yG), then both calculate scalar multiplication xyG. The equipment A and the equipment B utilize hashing function H to operate each scalar multiplication result xyF so as to obtain hash value h1 and h1'; if h1=h1', both equipment are legal. The system can be used in software and hardware environments, such as digital content protection interface, e-business, banking system, smart card, and identity authentication, etc.