US Patent 7885405 Multi-gigabit per second concurrent encryption in block cipher modes

One embodiment is a system adapted to encrypt one or more packets of plaintext data in cipher-block chaining (CBC) mode. The system includes a plurality of digital logic components connected in series, where respective components are operative to process one or more rounds of a block cipher algorithm. A plurality of N bit registers are respectively coupled to the plurality of digital logic components. An XOR component receives blocks of plaintext data and blocks of ciphertext data, and XORs blocks of plaintext data for respective plaintext packets with previously encrypted blocks of ciphertext data for those plaintext packets. The XOR component iteratively feeds the XOR'd blocks of data into a first of the plurality of the digital logic components. In addition, a circuit component is operative to selectively pass blocks of ciphertext data fed back from an output of a final logic component to the XOR component.