| 摘要 |
<p>Data encipherment and decipherment is achieved by converting blocks of input bits into blocks of output bits. The input bits are subjected to the operation of an algorithm, such as in accordance with the DES standard, involving a plurality of bit-permutation and/or substitution operations selected under the control of a key of substantial length. In the invention the operations available for selection by the key are changed in response to operation-control data received from an external source such as one involving the use of teletext or videotext, or using card or bar code readers, or direct keyboard input.</p> |
