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Nearly all modern hash functions are constructed by iterating a compression function. At FSE'04, Rogaway and Shrimpton [RS04] formalized seven security notions for hash functions: collision resistance (Coll) and three variants of second-preimage resistance (Sec, aSec, eSec) and preimage resistance (Pre, aPre, ePre). The main contribution of this paper is in… (More)

We develop a new generic long-message second preimage attack , based on combining the techniques in the second preimage attacks of Dean [8] and Kelsey and Schneier [16] with the herding attack of Kelsey and Kohno [15]. We show that these generic attacks apply to hash functions using the Merkle-Damgård construction with only slightly more work than the… (More)

Online ciphers encrypt an arbitrary number of plaintext blocks and output ciphertext blocks which only depend on the preceding plaintext blocks. All online ciphers proposed so far are essentially serial, which significantly limits their performance on parallel architectures such as modern general-purpose CPUs or dedicated hardware. We propose the first… (More)

In this paper we present new attack techniques to analyze the structure of hash functions that are not based on the classical Merkle Damgård construction. We extend the herding attack to concatenated hashes, and to certain hash functions that process each message block several times. Using this technique, we show a second preimage attack on the folklore "… (More)

CAESAR has caused a heated discussion regarding the merits of one-pass encryption and online ciphers. The latter is a keyed, length preserving function which outputs ciphertext blocks as soon as the respective plaintext block is received. The immediacy of an online cipher gives a clear performance advantage, yet it comes at a price. Since ciphertext blocks… (More)

In 2007, the US National Institute for Standards and Technology announced a call for the design of a new cryptographic hash algorithm in response to vulnerabilities identified in existing hash functions, such as MD5 and SHA-1. NIST received many submissions, 51 of which got accepted to the first round. At present, 14 candidates are left in the second round.… (More)

Given Nandi's attack on XLS, we intend to tweak COPA by removing XLS and extending the use of tag-splitting from short messages to arbitrary length messages. Formal specification to follow later.

The Advanced Encryption Standard (AES) is the most widely used block cipher. The high level structure of AES can be viewed as a (10-round) key-alternating cipher, where a t-round key-alternating cipher KAt consists of a small number t of fixed permutations Pi on n bits, separated by key addition: kt) are obtained from the master key K using some key… (More)

The notion of indifferentiability, introduced by Maurer et al., is an important criterion for the security of hash functions. Concretely, it ensures that a hash function has no structural design flaws and thus guarantees security against generic attacks up to the proven bounds. In this work we prove the indifferentiability of Grøstl, a second round SHA-3… (More)

The domain of lightweight cryptography focuses on cryptographic algorithms for extremely constrained devices. It is very costly to avoid nonce reuse in such environments, because this requires either a hardware source of randomness, or non-volatile memory to store a counter. At the same time, a lot of cryptographic schemes actually require the nonce… (More)