Patent ID: 8520839

Claim:
A data transmitter for transmitting successive blocks of user data, comprising: an encryption device operable to encrypt a first block of user data in order to obtain a first encryption result and encrypt a second block of user data, which follows the first block of user data, to obtain a second encryption result, the encryption device being further operable to use the first encryption result for encrypting the second block of user data; an extractor operable to extract a first portion of the first encryption result which is smaller than the first encryption result, and a second portion of the second encryption result which is smaller than the second encryption result; and a message formatter operable to combine the first block of user data and the first portion as a signature for the first block of user data to produce a first transmission packet, and combine the second block of user data and the second portion as a signature for the second block of user data to produce a second transmission packet.