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1. WO1992017959 - SELECTION DYNAMIQUE DE CLEF DE CRYPTAGE DESTINEE AUX EMISSIONS RADIO CRYPTEES

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

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Claims

1. A receiver capable of receiving encrypted messages which have unencrypted key identifiers, comprising:
storage means for storing a plurality of encryption keys each having a unique stored key identifier;
selection means for automatically selecting the proper key identifier to use from among the plurality of key identifiers in order to decrypt the incoming message prior to the encrypted message being received; and
a decryption means for decrypting the encrypted message using the encryption key which corresponds to the selected key identifier.

2. The receiver of claim 1 , wherein the selection means comprises a predetermined selection routine stored in the storage means which automatically selects the proper key identifier from among the plurality of key identifiers prior to receiving an encrypted message.

3. The receiver of claim 1 , wherein the receiver is a radio receiver.

4. The receiver of claim 2, further comprising:
a decoding means for decoding the unencrypted key identifier from the encrypted message which is received.

5. A transmitter, comprising:
storage means for storing a plurality of encryption keys each having a unique stored key identifier;
selection means for automatically selecting from among the plurality of key identifiers one of the key identifiers;
an encryption means responsive to the selection means for encrypting a message to be transmitted using the encryption key corresponding to the key identifier selected; and
transmitter means for transmitting the selected key identifier in an unencrypted format with the message encrypted by the encryption means.

6. A transmitter as defined in claim 5, wherein the selection means uses a random selection process to select from among the plurality of key identifiers one of the key identifiers.

7. A transmitter as defined in claim 5, wherein the selection means uses a predetermined selection process to select from among the plurality of key identifiers one of the key identifiers.

8. A transmitter as defined in claim 7, wherein the predetermined selection process chooses a different key identifier from among the plurality of stored key identifiers for every subsequent transmission.

9. A radio, comprising:
storage means for storing a plurality of encryption keys each having an unique stored key identifier;
transmitter means for transmitting messages;
control means having a first selection means for automatically selecting a key identifier, and a second selection means for use in automatically selecting a key identifier when the radio is receiving a message;
encryption means responsive to the first selection means for encrypting messages to be transmitted using the encryption key corresponding to the key identifier selected by the first selection means;
receiver means capable of receiving encrypted messages having unencrypted key identifiers;
said second selection means automatically selecting from among the plurality of stored key identifiers the key identifier which is to be used to properly decrypt the received encrypted message; and
decryption means for decrypting the received encrypted message using the encryption key which corresponds to the key identifier selected by the second selection means.

10. The radio as defined in claim 9, wherein the selected key identifier is transmitted in an unencrypted format with the encrypted message that is to be transmitted.

11. A communication system, comprising:
a control resource; and
a plurality of radios, each radio further comprising:
storage means for storing a plurality of encryption keys each having a unique stored key identifier;
transmitter means for transmitting messages;
control means having a first selection means for automatically selecting a key identifier, and a second selection means for use in automatically selecting a key identifier when the radio is receiving a message;
encryption means responsive to the first selection means for encrypting messages to be transmitted using the encryption key corresponding to the key identifier selected by the first selection means;
receiver means capable of receiving encrypted messages having unencrypted key identifiers;
said second selection means automatically selecting from among the plurality of stored key identifiers the key identifier which is to be used to properly decrypt the received encrypted message; and
decryption means for decrypting the encrypted message using the encryption key which corresponds to the key identifier selected by the second selection means.

12. The communication system of claim 11 , wherein the system is a trunked system, and the control resource is a trunked system central controller.

13. The radio of claim 11 , wherein the first selection means randomly selects one of the key identifiers prior to each
transmission.

14. The radio of claim 11 , wherein the first selection means follows a predetermined pattern of selecting key identifiers.

15. The radio as defined in claim 11 , wherein the selected key identifier is transmitted in an unencrypted format with the encrypted message that is to be transmitted.