Anti-spoof without error extension (ANSWER)
First Claim
1. Encryption apparatus for generating a deterministic psuedorandom keystream of data derived from a secret key and a prearranged initial state, and modulo-N add said random data to plain text data to form a cipher text data stream for transmission, in combination therewith apparatus for reducing "spoofing" which is the ability to alter received plain text by altering the transmitted cipher text, where N is a positive integer greater than one comprising:
- means responsive to said plain text data for altering a portion of said plain text data relative to a corresponding cipher text data according to a permutation function which varies according to a selected keystream, whereby one who does not possess said secret key cannot decrypt said cipher text, wherein "spoofing" is prevented from effecting said data stream.
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Accused Products
Abstract
There is disclosed encryption apparatus for generating a deterministic psuedorandom keystream of data derived from a secret key and a prearranged initial state and modulo-N adding the random data to plain text data to form a cipher text data stream to be transmitted. In order to reduce spoofing, which is the ability to alter received plain text by altering the transmitted cipher text there is means responsive to the plain text for altering a portion of the plain text data relative to corresponding cipher text data according to a permutation function which varies according to a selected keystream whereby one who does not possess said secret key cannot decrypt said cipher text and while preventing spoofing.
27 Citations
17 Claims
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1. Encryption apparatus for generating a deterministic psuedorandom keystream of data derived from a secret key and a prearranged initial state, and modulo-N add said random data to plain text data to form a cipher text data stream for transmission, in combination therewith apparatus for reducing "spoofing" which is the ability to alter received plain text by altering the transmitted cipher text, where N is a positive integer greater than one comprising:
means responsive to said plain text data for altering a portion of said plain text data relative to a corresponding cipher text data according to a permutation function which varies according to a selected keystream, whereby one who does not possess said secret key cannot decrypt said cipher text, wherein "spoofing" is prevented from effecting said data stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of encrypting plain text data for generating a deterministic pseudorandom keystream of data which are derived from a secret key and prearranged initial bits, and where plain text data is added to said random data to form a cipher text data stream for transmission to an encryption receiver, comprising the steps of:
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shifting N bits of plain text data for storage in a register, modulo N adding said shifted bits with N key stream bits, swapping a given number of added bits according to said keystream bits, performing said step of swapping a given number of times to provide an encrypted bit stream according to a bit permutation, wherein said bit permutation varies according to said keystream bits. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification