| 摘要 |
A block cipher supporting a selectable block size of bit granularity includes a recursive Feistal network structure having a plurality of substitution boxes (S-boxes), each S-box being generated by a message digest function used as a pseudo-random number generator and one of a plurality of keys. Rather than use message digest functions as dynamic S-boxes (as in the well-known Luby-Rackoff cipher), in the present invention S-boxes may be constructed from a key at cipher build time. For larger S-boxes, a subordinate Feistal network composed of S-boxes half the size of the desired S-box may be used. Once the S-box size, N, is sufficiently small (e.g., less than 16 input bits), a permutation of integers 0 . . . 2<N>-1 may be computed using the message digest as a cryptographic strength pseudo-random number generator (RNG) and the key. The generated integers may be used within the S-box as part of a look-up table for shuffling the input data to the S-box into encrypted output data.
|
