Abstract. On-Line Authenticated Encryption (OAE) combines privacy with data integrity and is on-line computable. Most block cipher-based schemes for Authenticated Encryption can be run on-line and are provably secure against nonce-respecting adversaries. But they fail badly for more general adversaries. This is not a theoretical observation only -in practice, the reuse of nonces is a frequent issue 1 .In recent years, cryptographers developed misuse-resistant schemes for Authenticated Encryption. These guarantee excellent security even against general adversaries which are allowed to reuse nonces. Their disadvantage is that encryption can be performed in an off-line way, only.This paper considers OAE schemes dealing both with nonce-respecting and with general adversaries. It introduces McOE, an efficient design for OAE schemes. For this we present in detail one of the family members, McOE-X, which is a design solely based on a standard block cipher. As all the other member of the McOE family, it provably guarantees reasonable security against general adversaries as well as standard security against nonce-respecting adversaries.
Abstract. Correct authenticated decryption requires the receiver to buffer the decrypted message until the authenticity check has been performed. 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 message 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 different platforms. Moreover, this paper introduces POET, a provably secure on-line AE scheme, which inherits pipelineability and chosen-ciphertextsecurity from POE and provides additional resistance against noncemisuse attacks.
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