Method and device for enciphering data to be transferred and for deciphering the enciphered data, and a computer system comprising such a device
First Claim
1. A method of enciphering data comprising the steps of:
- logically combining consecutive ones of a plurality of n-bit data words to be enciphered with an n-bit coding word so as to yield consecutive ones of resulting n-bit words;
varying a value of the n-bit coding word prior to logically combining the n-bit coding word with a next successive one of said n-bit data words to be enciphered in order to yield a corresponding one of the resulting n-bit words;
supplying consecutive n-bit words to a product cipher circuit;
modifying, in said product cipher circuit and under the control of an m-bit key, each one of said n-bit words a plurality of times in a corresponding plurality of consecutive modification stages of said product cipher circuit to yield a corresponding enciphered data word, wherein each of said modification stages and n and m are both pre-defined integers;
said modifying step comprising the step of;
successively and alternately permuting and substituting said each n-bit word a plurality of times under the control of said key.
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Abstract
Method and device for enciphering data words of a word width of n bits, in particular data words to be written in a computer storage, wherein a product cipher circuit comprises alternately one from a plurality of permutation boxes with n inputs and n outputs and one from a plurality of substitution boxes with n inputs and n outputs, each of these boxes being under the control of a specific part of an m-bits key. In the product cipher circuit the data words are consecutively enciphered in whole and the enciphering device can be regarded as a delay line. The data words to be enciphered can be combined with coding words which depend on the specific sector of the computer storage, in particular a hard storage disk unit, where the data words are stored. The sector-specific coding words and/or the m-bits key can be combined with a key to be entered by a user.
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Citations
31 Claims
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1. A method of enciphering data comprising the steps of:
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logically combining consecutive ones of a plurality of n-bit data words to be enciphered with an n-bit coding word so as to yield consecutive ones of resulting n-bit words; varying a value of the n-bit coding word prior to logically combining the n-bit coding word with a next successive one of said n-bit data words to be enciphered in order to yield a corresponding one of the resulting n-bit words; supplying consecutive n-bit words to a product cipher circuit; modifying, in said product cipher circuit and under the control of an m-bit key, each one of said n-bit words a plurality of times in a corresponding plurality of consecutive modification stages of said product cipher circuit to yield a corresponding enciphered data word, wherein each of said modification stages and n and m are both pre-defined integers;
said modifying step comprising the step of;successively and alternately permuting and substituting said each n-bit word a plurality of times under the control of said key. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of deciphering enciphered data comprising the steps of:
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supplying consecutive n-bit enciphered words to a product cipher circuit; modifying, in said product cipher circuit and under the control of an m-bit key, each one of said n-bit enciphered words a plurality of times in a corresponding plurality of consecutive modification stages of said product cipher circuit to yield a corresponding one of a plurality of deciphered data words, wherein each of said n-bit enciphered words is modified only once by each one of said modification stages and n and m are both pre-defined integers;
said modifying step comprising the step of;successively and alternately permuting and substituting said each n-bit enciphered word a plurality of times under the control of said key; and said method further comprises the steps of; logically combining consecutive ones of the deciphered words with an n-bit coding word so as to yield consecutive ones of n-bit deciphered data words; and varying a value of the n-bit coding word prior to logically combining the n-bit coding word with a next successive one of said n-bit deciphered words in order to yield a current corresponding one of the n-bit deciphered data words. - View Dependent Claims (8, 9, 10, 11, 12)
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13. Apparatus for enciphering n-bit data words comprising:
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a product cipher circuit, having as input signals consecutive n-bit words and an m-bit key, producing a sequence of corresponding enciphered n-bit data words and having alternately one from a plurality of permutation boxes with n inputs and n outputs and one from a plurality of substitution boxes with n inputs and n outputs, each of said permutation and substitution boxes being under the control of a specific part of the m-bit key, wherein each consecutive one of the n-bit words is permuted or substituted only once by each respective one of said permutation and substitution boxes and n and m are pre-defined integers; and a modulo 2 adder wherein a first input to said adder receives n-bit data words to be enciphered, a second input to the adder is linked to the output of the product cipher circuit and receives the n-bit enciphered data words and the output of the adder is linked to and provides said n-bit words to an input of the product cipher circuit, wherein the adder logically combines each one of the n-bit enciphered data words produced by said product cipher circuit with a next successive one of said n-bit data words to be enciphered in order to yield a corresponding one of the n-bit words. - View Dependent Claims (14, 15, 16)
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17. Apparatus for deciphering n-bit enciphered data words comprising:
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a product cipher circuit, having as input signals consecutive n-bit enciphered words and an m-bit key, for producing a sequence of corresponding deciphered n-bit data words and having alternately one from a plurality of permutation boxes with n inputs and n outputs and one from a plurality of substitution boxes with n inputs and n outputs, each of said permutation and substitution boxes being under the control of a specific part of the m-bit key, wherein each consecutive one of the n-bit enciphered words is permuted or substituted only once by each respective one of said permutation and substitution boxes and n and m are pre-defined integers; and a modulo 2 adder wherein a first input to said adder is linked to the output of the product cipher circuit and receives the deciphered n-bit data words, a second input to the adder is linked to an input to the product cipher circuit and receives the enciphered n-bit data words to be deciphered and an output of the adder provides the deciphered n-bit enciphered data words, wherein the adder logically combines each one of the deciphered n-bit words produced by said product cipher circuit with a next successive one of said enciphered n-bit data words to be deciphered in order to yield a current corresponding one of the deciphered n-bit words. - View Dependent Claims (18, 19, 20)
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21. A computer system comprising:
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a central processor; a hard disk storage unit; a bus linking the central processor and the disk storage unit; and means, connected to said bus, for enciphering n-bit data words as said data words are transferred, along the bus, between said central processor and said hard disk storage unit, said enciphering means comprising; a product cipher circuit, having as input signals consecutive n-bit words and an m-bit key, producing a sequence of corresponding enciphered n-bit data words and having alternately one from a plurality of permutation boxes with n inputs and n outputs and one from a plurality of substitution boxes with n inputs and n output, each of said permutation and substitution boxes being under the control of a specific part of the m-bit key, wherein each consecutive one of the n-bit words is permuted or substituted only once by each respective one of said permutation and substitution boxes and n and m are pre-defined integers; a modulo 2 adder wherein a first input to said adder receives n-bit data words to be enciphered, a second input to the adder is linked to the output of the product cipher circuit and receives the n-bit enciphered data words and the output of the adder is linked to and provides said n-bit words to an input of the product cipher circuit, wherein the adder logically combines each one of the n-bit enciphered data words produced by said product cipher circuit with a next successive one of said n-bit data words to be enciphered in order to yield a corresponding one of the n-bit words; and switching means for linking at predetermined points in time the second input of the modulo 2 adder to a circuit which generates an n-bit initial coding word. - View Dependent Claims (22, 23)
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24. A computer system comprising:
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a central processor; a hard disk storage unit; a bus linking the central processor and the disk storage unit; and means, connected to said bus, for enciphering n-bit enciphered data words as said enciphered data words are transferred, along the bus, between said central processor and said hard disk storage unit, said deciphering means comprising; a product cipher circuit, having as input signals consecutive n-bit enciphered words and an m-bit key, producing a sequence of corresponding deciphered n-bit data words and having alternately one from a plurality of permutation boxes with n inputs and n outputs and one from a plurality of substitution boxes with n inputs and n output, each of said permutation and substitution boxes being under the control of a specific part of the m-bit key, wherein each consecutive one of the n-bit enciphered words is permuted or substituted only once by each respective one of said permutation and substitution boxes and n and m are pre-defined integers; a modulo 2 adder wherein a first input to said adder is linked to the output of the product cipher circuit and receives the deciphered n-bit data words, a second input to the adder is linked to an input to the product cipher circuit and receives the enciphered n-bit data words to be deciphered and an output of the adder provides the deciphered n-bit enciphered data words, wherein the adder logically combines each one of the deciphered n-bit words produced by said product cipher circuit with a next successive one of said enciphered n-bit data words to be deciphered in order to yield a current corresponding one of the deciphered n-bit words; and switching means for linking at predetermined points in time the second input of the modulo 2 adder to a circuit which generates an n-bit initial coding word. - View Dependent Claims (25, 26)
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27. A method of enciphering data comprising the steps of:
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logically combining consecutive ones of a plurality of n-bit data words to be enciphered with an n-bit coding word so as to yield consecutive ones of resulting n-bit words; varying a value of the n-bit coding word prior to logically combining the n-bit coding word with a next successive one of said n-bit data words to be enciphered in order to yield a corresponding one of the resulting n-bit words; supplying consecutive n-bit words to a product cipher circuit; modifying, in said product cipher circuit and under the control of an m-bit key, each one of said n-bit words a plurality of times in a corresponding plurality of consecutive modification stages of said product cipher circuit to yield a corresponding enciphered data word, wherein n and m are both pre-defined integers;
said modifying step comprising the step of;successively and alternately permuting and substituting said each resulting n-bit word a plurality of times under the control of said key. - View Dependent Claims (28, 29, 30, 31)
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Specification