Authenticated Streamwise On-line Encryption

In Blockwise On-line Encryption, encryption and decryption return an output block as soon as the next input block is received. In this paper, we introduce Authenticated Streamwise Online Encryption (ASOE), which operates on plaintexts and ciphertexts as streams of arbitrary length (as opposed to fixed-sized blocks), and thus significantly reduces message expansion and end-to-end latency. Also, ASOE provides data authenticity as an option. ASOE can therefore be used to efficiently secure resource-constrained communications with real-time requirements such as those in the electric power grid and wireless sensor networks. We investigate and formalize ASOE ’s strongest achievable notion of security, and present a construction that is secure under that notion. An instantiation of our construction incurs zero end-to-end latency due to buffering and only 48 bytes of message expansion, regardless of the plaintext-size.