An automatic resynchronization technique for secure communication with stream ciphers

Synchronous stream ciphers require perfect synchronization between the encryptor and the decryptor. However, in some applications, the risk of synchronization loss cannot be eliminated completely. To reduce the risk, fixed resynchronization, achieved by inserting a synchronization pattern (SP) and a session key (SK) in ciphertext at fixed timesteps, is used in some cases. But there are problems associated with fixed resynchronization. In the paper, we propose a new resynchronization by using the same key-stream after skipping some keystreams at fixed timesteps, without inserting an SP and an SK. The proposed method is adequate for asynchronous (start/stop) data terminal equipments which are used in low-speed sensor networks and is more effective than fixed resynchronization in a noisy channel, because it is less dependent on channel states than fixed resynchronization.