A transmitting/receiving system includes a transmitting apparatus that transmits, to another apparatus, first encrypted data obtained by encrypting stream data including consecutive unit data items in accordance with a first encryption technique prescribing that, when the stream data is encrypted for each item, keys used for encrypting the items are updated, and a receiving apparatus that receives and decrypts the first data from the transmitting apparatus in accordance with a first decryption technique. The transmitting apparatus includes an encryptor that outputs second encrypted data obtained by generating data including a predetermined number of keys, and encrypting the data in accordance with a second encryption technique, a transmitter that transmits the second data from the encryptor to the receiving apparatus. The receiving apparatus includes a key receiver that receives the second data from the transmitter, and a key decryptor that decrypts the second data in accordance with a second decryption technique.