Patent ID: 8351599

Claim:
A cryptographic device for fast session switching, comprising: a processor; a block cipher algorithm executer configured to perform encryption or decryption on input data using an initialization vector and a round key corresponding to a current session; an initialization vector manager configured to store an initialization vector input from outside of the cryptographic device and an initialization vector received from the block cipher algorithm executer, and providing the initialization vector corresponding to the current session to the block cipher algorithm executer; and a session round key generator configured to store a session key input from outside of the cryptographic device, generate a plurality of round keys needed to perform encryption or decryption for a first block of the input data, based on a session key corresponding to the current session and provide the round keys to the block cipher algorithm executer during rounds only in which the block cipher algorithm executer performs encryption or decryption on the first block of the input data, wherein the session round key generator is further configured to store the generated round keys for the first block of the input data and provide them to the block cipher algorithm executer while encryption or decryption is performed on remaining blocks of the input data by the block cipher algorithm executer, wherein the initialization vector received from the block cipher algorithm executer is an initialization vector changed while the encryption or decryption is performed.