Remotely keyed encryption with Java cards: a secure and efficient method to encrypt multimedia streams

Multimedia data streams often require encryption; examples include digital pay-TV and workstation video conferencing. The secret key should be carried in a personal device such as a smart card or an i-button. However, the processor on such a device is too slow to encrypt/decrypt the multimedia stream in real time. We show that remotely keyed encryption can be used to solve the problem: for each block of multimedia data, the host sends a data-dependent challenge to the card, the card computes a session key based on the challenge and the secret key and sends it back to the host. Encryption/decryption of the main data stream is then entirely done on the (fast) host. The secret key never leaves the card. We also present experimental performance results for our scheme using an i-button programmed in Java and a PC as the host