| 摘要 |
A method and apparatus for encryption of data between a first device (12) an d a second device (30), in which one or more precalculated key pairs (41) are stored in a memory of the first device (12), the or each key pair comprising a session key and an encrypted version of the session key. The encrypted versi on is passed to the second device (30), which decrypts (42) the session key, th is session key being thereafter used to encrypt data communicated from the seco nd device (30) to the first device (12) and/or vice versa. The invention is particularly applicable to a digital television system in which data, notabl y control word data, is to be communicated in encrypted form between a decoder and an associated portable security module. |
