Patent ID: 8108674

Claim:
A transmitting/receiving system comprising: a transmitting apparatus configured to transmit first encrypted data obtained by encrypting stream data including a plurality of consecutive unit data items in accordance with a first encryption technique, the first encryption technique prescribing that, when the stream data is sequentially encrypted for each unit data item, a plurality of keys to encrypt the unit data items are periodically updated according to predetermined rules, the transmitting apparatus including a key encryptor configured to output second encrypted data, the second encrypted data being obtained by generating M-bit data including at least one N-bit key from the plurality of keys used to generate the first encrypted data such that a total amount of N-bits of the at least one N-bit key is less than the generated M-bit data and any remaining bits of the M-bit data are padded, and encrypt the generated M-bit data in accordance with a second encryption technique, and a key transmitter configured to transmit the second encrypted data output from the key encryptor to the receiving apparatus; and a receiving apparatus configured to receive and decrypt the first encrypted data in accordance with a first decryption technique corresponding to the first encryption technique by using the plurality of keys used to generate the first encrypted data, the receiving apparatus including a key receiver configured to receive the second encrypted data transmitted from the key transmitter, and a key decryptor configured to decrypt the second encrypted data in accordance with a second decryption technique corresponding to the second encryption technique, wherein the key encryptor generates, as one information-data item, data including one Advanced-Encryption-Standard key and link-encryption-attribute data, and the key transmitter transmits the second encrypted data to the receiving apparatus by transmitting data obtained by superimposing the second encrypted data on the first encrypted data.