Method and system for machine enciphering and deciphering
First Claim
1. Method for the enciphering and authorized deciphering of multi-digit data, comprisingsubjecting successive data segments, under control of corresponding segments of an enciphering key, to a substitution operation generating a modified version of the data segment;
- andin each substitution operation, selecting one of several given modification modes, as a predetermined function of a data segment and the corresponding key segment for changing the enciphering key before the next substitution operation upon the next corresponding segment.
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Abstract
Variable length data words are processed segment-by-segment together with corresponding segments of an enciphering key. As a function of the contents of a data segment, one of several modification modes is chosen. In accordance with the chosen modification mode, the enciphering key is changed following each enciphering operation of a segment. The described steps are preferably carried out three times for the full data word. The result of the third cycle represents the enciphered data word. Deciphering is effected in the same manner.
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Citations
25 Claims
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1. Method for the enciphering and authorized deciphering of multi-digit data, comprising
subjecting successive data segments, under control of corresponding segments of an enciphering key, to a substitution operation generating a modified version of the data segment; - and
in each substitution operation, selecting one of several given modification modes, as a predetermined function of a data segment and the corresponding key segment for changing the enciphering key before the next substitution operation upon the next corresponding segment. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Method for the enciphering and authorized deciphering of multi-digit data, comprising
subjecting to a substitution operation a data segment and a key segment of a first key word (first enciphering key half) to generate a modified version of the data segments, selecting one of several different modification operations by means of which the first key word is modified before the next substitution operation, and repeating the above steps with the remaining data segments of the data register and the corresponding segments of the repeatedly modified first key word, such that with the modified version of the data a permutation operation is carried out, the result of which again causes a data segment and a key segment of a second key word (second enciphering key half) to be both subjected to a substitution operation which again generates a modified version of the data segment, and to also select one of several different modification operations, by means of which the second key word is modified before the next substitution operation, said last steps being repeated with the remaining segments of the modified data and corresponding segments of the repeatedly modified second key word.
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14. System for the enciphering and authorized deciphering of multi-digit data, comprising:
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data register means for storing the data to be enciphered and deciphered; key register means for storing an enciphering key for operating on said data; substitution means, connected to said data register means and said key register means, for subjecting successive data segments, under control of corresponding segments of an enciphering key, to a substitution operation generating a modified version of the data segment; and modification means, connected to the outputs of said data register means and said key register means, for changing, as a function of the data segments and the corresponding key segments, the enciphering key before next substitution operation, said modification means including means for selecting, in each substitution operation, one of several given modification modes. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification