Patent ID: 8538021

Claim:
A sending apparatus for transmitting a frame including one or more data packets, the apparatus comprising: an encryption unit which encrypts each of the data packets on the basis of a cryptographic key and an initialization vector that is generated from a frame number of the frame to be transmitted, the initialization vector selectively including either a shrunken bit series obtained by replacing a specified number of high-order bits of the frame number with zeros, or an extended bit series obtained by adding to the frame number a specified number of counter bits indicating how many times the frame number has circulated, wherein the number of high-order bits to be replaced and the number of counter bits to be added are programmable with parameters, and wherein the cryptographic key is changed in each circulation cycle of the shrunken bit series or extended bit series that is selected; and a sending unit which transmits the frame including the data packets encrypted by the encryption unit.