Mitigating Both Data Corruption and Content Replay Attacks with Implicit Data Integrity We study the security of the recently proposed implicit integrity methodology. Implicit integrity is a novel methodology that supports corruption detection without producing, storing or verifying mathematical summaries of the content such as MACs or ICVs, as typically done today. The main idea behind implicit integrity is that, whereas typical user data demonstrate patterns such as repeated bytes or words, decrypted data resulting from corrupted ciphertexts no longer demonstrate such patterns. Thus, by checking the entropy of decrypted ciphertexts, corruption can be possibly detected. Past contributions to the implicit integrity methodology have focused on observed patterns on client and server data that motivate the methodology, entropy definitions for arbitrarily small messages, and constructions that mitigate data corruption attacks. In this paper, we extend the known analytical results concerning implicit integrity addressing content replay attacks as well. We demonstrate that the class of cryptographic constructions known as xe2x80x98random oracles according to observer functionsxe2x80x99, which has been proposed for mitigating data corruption attacks, is actually simultaneously secure under two different adversary models: an input perturbing adversary performing content corruption attacks, and an oracle replacing adversary performing content replay attacks.

IVP: A Three Level ConfusionDiffusion Network Supporting Implicit Data Integrity We present a cryptographic construction called IVP and study its security properties. IVP is a three level confusiondiffusion network that supports confidentiality and data integrity without requiring any message expansion of the content, such as, for example, for the computation of a MAC. We demonstrate that IVP is in the recently proposed class of cryptographic constructions called xe2x80x98Random Oracles according to Observer functionsxe2x80x99 (RO2). These constructions support a new notion of data integrity called xe2x80x98implicitxe2x80x99 data integrity, which is based on the fact that user data usually demonstrate some patterns. If some ciphertext becomes corrupted, then the resulting plaintext no longer demonstrates such patterns. Thus, defense against data corruption attacks becomes possible by hardening the computation of ciphertext values, the plaintext of which demonstrates patterns. The encryption key is considered unknown.We show that IVP supports implicit data integrity and is secure in input perturbing and oracle replacing adversary models. The security of IVP is associated with a pattern which is frequently encountered among client and server data. This is the pattern of encountering 4 or more 16bit words being equal to each other in a set of 32 words. The cryptographic strength of IVP is 30.215 bits, which is sufficient for defending against online data corruption and content replay attacks. Computationally, IVP is much lighter than other authenticated encryption approaches requiring only two additional rounds of AES, beyond the AES standard encryption rounds in the critical path. These correspond to some minimal computation overhead.