Encrypted data transmission system employing means for randomly altering the encryption keys

CAFC
  • US 5,412,730 A
  • Filed: 04/23/1992
  • Issued: 05/02/1995
  • Est. Priority Date: 10/06/1989
  • Status: Expired due to Term
First Claim
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1. A method for transmitting data comprising a sequence of blocks in encrypted form over a communication link from a transmitter to a receiver comprising, in combination, the steps of:

  • providing a seed value to both said transmitter and receiver,generating a first sequence of pseudo-random key values based on said seed value at said transmitter, each new key value in said sequence being produced at a time dependent upon a predetermined characteristic of the data being transmitted over said link,encrypting the data sent over said link at said transmitter in accordance with said first sequence,generating a second sequence of pseudo-random key values based on said seed value at said receiver, each new key value in said sequence being produced at a time dependent upon said predetermined characteristic of said data transmitted over said link such that said first and second sequences are identical to one another a new one of said key values in said first and said second sequences being produced each time a predetermined number of said blocks are transmitted over said link, anddecrypting the data sent over said link at said receiver in accordance with said second sequence.

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