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Dynamic encryption key selection for encrypted radio transmissions

  • US 5,222,137 A
  • Filed: 04/03/1991
  • Issued: 06/22/1993
  • Est. Priority Date: 04/03/1991
  • Status: Expired due to Fees
First Claim
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1. A method for transmitting encrypted messages between first and second radios, each of the radios including a plurality of encryption keys each having a unique key identifier, each of the first and second radios also each having an encryption key selection program, the method comprising the steps of:

  • at the first radio;

    selecting a key identifier from among the plurality of key identifiers;

    encrypting a message that is to be transmitted to the second radio using the encryption key which corresponds to the selected key identifier;

    appending the key identifier to the encrypted message;

    transmitting the encrypted message and key identifier to the second radio;

    selecting from among the plurality of encryption keys a new encryption key using the encryption selection program found in the first radio;

    at the second radio;

    receiving the encrypted message from the first radio;

    decoding the key identifier sent with the encrypted message;

    decrypting the encrypted message using the encryption key which corresponds to the decoded key identifier; and

    selecting a new encryption key using the encryption selection program found in the second radio which matches the new encryption key selected by the first radio.

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