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Cryptosystem for cellular telephony

  • US 5,159,634 A
  • Filed: 09/13/1991
  • Issued: 10/27/1992
  • Est. Priority Date: 09/13/1991
  • Status: Expired due to Term
First Claim
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1. In a communications system, a method of transforming a set of message signals representing a message, the method which includes the steps ofencrypting said set of message signals with an encryption process and a set of key signals to form a set of first intermediate signals,altering said set of first intermediate signals in accordance with an involutory transformation to form a set of second intermediate signals, and decrypting said set of second intermediate signals with a decryption process which is the inverse of said encryption process to form a set of output signals,Characterized in that:

  • said step of altering comprises the step of modifying a first subset of said set of first intermediate signals with an unkeyed transformation based on a second subset of said set of first intermediate signals.

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