Abstract: An encoder for providing encrypted data for transmission via a transmission medium includes an encryption unit that is configured to encrypt data received at the encoder block by block and a processing unit. The processing unit is configured to randomly distribute an encrypted data block to a plurality of channels that are allocated to the transmission medium and to provide a sub-block, which includes part of the encrypted data block, to be transmitted via one of the channels, together with a channel identification allocated to the channel and a code value that is based on the encrypted data in the sub-block to be transmitted and the channel identification, for transmission via the allocated channel of the transmission medium.