AbstractA key distribution system based on identification information is presented. The system is based on the Diffie‐Hellman public key distribution scheme (DH‐PKDS) and has an identity authentication function. It uses identification information on individual users instead of a public file employed in the DH‐PKDS. The system proposed here does not require any services of a center to distribute work keys, not does it require users to maintain directories of information for the generation of keys. This allows key management for cryptosystems to be simplified.In this paper, two kinds of identity‐based key distribution systems are proposed. One uses two‐way (interactive) communication to distribute work keys, and the other uses one‐way communication. They are applied to communication networks, on‐line talk networks and mail networks, for instance. Modular exponentiations of large numbers used in the networks are implemented with digital signal processors.