Key distribution system for mail systems using ID-related information directory

A key distribution system suitable for mail systems is presented. It realizes a secure cryptosystem that is convenient for users and, moreover, can be easily implemented in present computer networks. The system uses a public directory, which contains each user's ID-related information, but is strong against forgery. A sender generates a key and key information which depends on the receiver, and sends the key information along with the encrypted message. Only the intended receiver can obtain the common key from the key information and decrypt the message. He can also convince himself that the sender is authentic. Since a random number is used in generation of a key and its information, keys are different in every mail item. The paper further discusses the implementation of the proposed system on an existing personal computer network. For faster execution, a digital signal processor is adopted. A modular algorithm suitable for the processor is presented.