Encrypting device having session memory bus

An encryption device equipped with a session memory bus is provided to reduce the access delay time to a session memory of an encryption processor corresponding to the use of a shared data bus. An external session memory(270) divides and stores encryption information for all sessions. An encryption processor(200) encrypts or decrypts input data by using the encryption information, and includes an internal session memory(230) and an internal session memory bus. The internal session memory stores the encryption information for the sessions. The internal session memory bus is connected to the internal session memory. An external session memory bus is connected to an external session memory and the encryption processor. A CPU(280) transmits and receives data to and from the external session memory through the encryption processor.