OPTICAL SUBSCRIBER LINE TERMINATING DEVICE AND OPTICAL SUBSCRIBER END STATION DEVICE

摘要

PROBLEM TO BE SOLVED: To efficiently execute the receiving control and decoding processing of information. SOLUTION: A first storing means M11a stores ciphering setting information which is being used presently. A second storing means M11b stores newly updated ciphering setting information. A ciphering setting information storing means 11 includes the means M11a and the means M11b, executes storage control on the means M11a and the means M11b. A ciphered information deciphering processing means 12 receives an information stream having a frame constitution and then validates stored ciphering setting information from the next frame to execute deciphering processing to a ciphered information part shown by ciphering setting information from the next frame.