Encryption system for time division multiplexed networks

An encryption system is provided for interfacing a time division multiplexing (TDM) telecommunications arrangement with an encryption device for the scrambling of data received by the telecommunications arrangement. The telecommunications arrangement produces a TDM data stream formatted into TDM frames including a predetermined number of TDM framing bits and corresponding framing bit locations. At a local side of the system, a first TDM data stream is received and sampled, and the TDM framing bit information is detected and stored therefrom. The data stream is then sent to an encryptor for encryption, and thereafter the TDM framing bit information is reinserted into the corresponding bit locations of the encrypted data stream. As a result, the TDM framing bit information is passed around the encryptor. This encrypted data stream and framing bit information is transmitted to a remote station across a TDM (e.g., T1) communications network. At the remote station, the TDM framing bit information is again detected and stored, the encrypted data stream is decrypted, and the TDM framing bit information is reinserted to the corresponding locations.

Patent #: 5161191 Issue Date: November 3, 1992