APPARATUS FOR GENERATING ENCRYPTION/DECRYPTION LOOK-UP TABLES USING A SESSION KEY

摘要

An encryption/decryption apparatus enables encrypted communication between two stations each incorporating such an apparatus. The apparatus is arranged to generate a set of look-up tables in accordance with a session key and temporarily store these tables in memory (18), and to convert each successive element (e.g. character) of a message to a code through use of the look-up tables. The session key can be changed as often as desired but the fresh set of look-up are created quickly each time; then the conversion process for each element of the message is carried out quickly yet maintaining a high level of security.