Method and apparatus for generating encryption stream ciphers
First Claim
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1. A method for generating a stream cipher comprising:
- selecting a finite field having an order greater than one;
selecting a recurrence relation over said finite field;
selecting an output equation;
computing said stream cipher in accordance with said recurrence relation and said output equation; and
wherein said recurrence relation and said output equation have distinct pair distances.
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Abstract
A method and apparatus for generating encryption stream ciphers. The recurrence relation is designed to operate over finite fields larger than GF(2) and is maximal length. An output equation generates the output based on a plurality of elements in the shift register used to implement the recurrence relation. The recurrence relation and the output equation are selected to have distinct pair distances such that, as the shift register shifts, no particular pair of elements of the shift register are used twice in either the recurrence relation or the output equation.
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Citations
32 Claims
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1. A method for generating a stream cipher comprising:
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selecting a finite field having an order greater than one;
selecting a recurrence relation over said finite field;
selecting an output equation;
computing said stream cipher in accordance with said recurrence relation and said output equation; and
wherein said recurrence relation and said output equation have distinct pair distances. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
initializing said generator with a secret key.
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19. The method of claim 18 wherein said initializing step comprises the steps of:
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adding a least significant byte of said secret key to said recurrence relation;
shifting said secret key by one byte; and
repeating said adding step and said shifting steps until all bytes in said secret key are added to said recurrence relation.
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20. The method of claim 18 wherein a length of said secret key is less than an order of said recurrence relation.
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21. The method of claim 18 further comprising the step of:
initializing said generator with a per frame key.
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22. The method of claim 21 wherein a length of said per frame key is four octets long.
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23. The method of claim 21 wherein said initializing said generator with a per frame key step is performed for each data frame.
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24. The method of claim 21 wherein said initializing said generator with a per frame key step comprises the steps of:
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adding a least significant byte of said per frame key to said recurrence relation;
shifting said per frame key by three bits;
repeating said adding step and said shifting steps until all bytes in said per frame key are added to said recurrence relation.
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25. The method of claim 24 wherein said initializing said generator with a per frame key step further comprises the step of:
adding said least significant byte of said per frame key to a most significant byte of said per frame key.
- 26. An apparatus for generating a stream cipher, comprising a processor for receiving instructions for performing a recurrence relation and an output equation, said processor performing manipulations on elements in accordance with said instructions, wherein said recurrence relation and said output equation have distinct pair distances, and wherein said recurrence relation is defined over a finite field having an order of greater than one.
Specification