| 摘要 |
A cryptographic system is used for the secure transmission of digitized signals to a plurality of receivers. At the transmission end, a key consisting of two blocks, each including a plurality of key fragments, is generated. For each transmission session, different sets of key fragments may be periodically selected from one of the key blocks and used to encrypt the signals. Data indicative of the set selection is generated. The key is distributed to each receiver. The set selection data is transmitted to all receivers along with the encrypted signals and used to construct the key fragment set for decryption of the transmitted signals. During the transmission session, the other key block may be varied to form a replacement key which is distributed to each receiver. At the end of the session, the functions of the key blocks are interchanged in all receivers at one time by selecting a set in the varied key block for use in encryption and decryption. |
