| 摘要 |
1526652 Ciphering INTERNATIONAL BUSINESS MACHINES CORP 20 April 1977 [26 April 1976] 16347/77 Heading H4P A block-cipher system uses a user supplied key {represented by function f k below} to control the cryptographic operation, an input block of data x i being modified prior to the operation by compounding it according to disclosed rules of composition, (+), preferably modulo-2 addition, with a prior encrypted segment, preferably the previously enciphered block y j . The alogorithm takes the form y j =f k {x i (+)g(y j )} g being the identity, or a function which interchanges the two halves of y j . Means for handling short blocks of data is also disclosed, operating in essentially the same manner. The compounding, which may alternatively be simple addition, or controlled circular shift, may be confined to blocks within a record of blocks, or many involve crossing record boundaries. Hardware and microprogram are discussed in detail, the former being usable for either enciphering or deciphering. The first block of a record is compounded with a preselected set of bits.
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