| 摘要 |
A decryption apparatus (109) comprises a key stream generator (111) generating a local decryption key stream. It furthermore comprises a synchronization value receiver (201) receiving key stream synchronization values. A synchronization processor (203) implements a state machine which may operate in a synchronized state (303) wherein the communication is decrypted using the local key stream, a non-synchronized state (301) wherein the local key stream is not synchronized, or in an uncertain synchronization state (305) wherein the communication is decrypted using the local key stream and wherein the local key stream is synchronized to each new received synchronization value. The synchronization processor (203) furthermore comprises a transition controller (213) operable to transition from the synchronized state to the non-synchronized state in response to a first criterion and to the uncertain synchronization state in response to a second criterion.
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