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Method and arrangement for ciphering information transfer

  • US 6,813,355 B1
  • Filed: 02/12/1999
  • Issued: 11/02/2004
  • Est. Priority Date: 02/13/1998
  • Status: Expired due to Term
First Claim
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1. A method for ciphering a mobile communications connection between at least two devices wherein information to be transferred is modulated into at least one burst of a certain fixed length and the information to be transferred is ciphered according to a predetermined algorithm and ciphering key, whereininformation transferred in one burst is divided into at least two blocks, the first block is ciphered using a first ciphering key (Kcn1), the second block is ciphered using a second ciphering key (Kcn2), said first and second ciphering keys are different from each other, at least one of said first and second ciphering keys (Kcns) is generated on the basis of a parameter (COUNT) transferred on a radio frequency information transfer channel of the mobile communications connection, and the number of information blocks transferred in a burst is changed during the connection between said two devices.

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