Pipelineable On-Line Encryption

Abstract. Correct authenticated decryption requires the receiver to buffer the decrypted message until the authenticity check has been per-formed. In high-speed networks, which must handle large message frames at low latency, this behavior becomes practically infeasible. This paper proposes CCA-secure on-line ciphers as a practical alternative to AE schemes since the former provide some defense against malicious mes-sage modifications. Unfortunately, all published on-line ciphers so far are either inherently sequential, or lack a CCA-security proof. This paper introduces POE, a family of on-line ciphers that combines provable security against chosen-ciphertext attacks with pipelineability to support efficient implementations. POE combines a block cipher and an ǫ-AXU family of hash functions. Different instantiations of POE are given, based on different universal hash functions and suitable for differ-ent platforms. Moreover, this paper introduces POET, a provably secure on-line AE scheme, which inherits pipelineability and chosen-ciphertext-security from POE and provides additional resistance against nonce-misuse attacks