In the field of information security, CPK is the abbreviation of "combined public key", which is called combined public key in Chinese. It is an encryption algorithm, which can generate large-scale keys with very few resources.

Combined public key's ID-based digital signature protocol and key exchange protocol satisfy the scale of proof and the directness of verification, truly realize Shamir's idea, and open up a new way to solve the scale by combination. In 2007, on the basis of combined public key, a two-factor compound combined public key TF-CPK was formed, which retained the advantages of combined public key, enhanced security, realized compound digital signature and key exchange mechanism respectively, and solved the difficulty of individual defining signature key under centralized management mode.

CPK principle

CPK key management system is a key generation and management system based on discrete logarithm problem. According to the mathematical principle of discrete logarithm problem, it constructs a public key and a private key matrix, and uses hash function and cryptographic transformation to map the entity's identity into the row coordinate and column coordinate sequence of the matrix, so as to select and combine the matrix elements, and generate a large number of public key and private key pairs composed of public key and private key, thus realizing identity-based super-large-scale key generation and distribution.

Key production and management in CPK key management system are centralized. It accepts applications from entities through registration departments, production departments and distribution departments, checks identities, generates private keys based on identities, and distributes them to entities statically. The private key of each entity is stored in a decentralized way, and the public key matrix can be stored in the most accessible way for any entity to call conveniently, so that any entity can generate its own public key according to the identification of the other party.

The above contents refer to Baidu Encyclopedia -CPK.