In one embodiment, data communication apparatus includes packet processing circuitry to receive data from a memory responsively to a data transfer request, and cryptographically process the received data in units of data blocks using a block cipher so as to add corresponding cryptographically processed data blocks to a sequence of data packets, the sequence including respective ones of the cryptographically processed data blocks having block boundaries that are not aligned with payload boundaries of respective one of the packets, such that respective ones of the cryptographically processed data blocks are divided into two respective segments, which are contained in successive respective ones of the packets in the sequence, and a network interface which includes one or more ports for connection to a packet data network and is configured to send the sequence of data packets to a remote device over the packet data network via the one or more ports.