105 research outputs found
Collision-resistant hash function based on composition of functions
cryptographic hash function is a deterministic procedure that compresses an
arbitrary block of numerical data and returns a fixed-size bit string. There
exist many hash functions: MD5, HAVAL, SHA, ... It was reported that these hash
functions are not longer secure. Our work is focused in the construction of a
new hash function based on composition of functions. The construction used the
NP-completeness of Three-dimensional contingency tables and the relaxation of
the constraint that a hash function should also be a compression function.Comment: 18 pages, 1 figure. The preliminary version of this paper was
published in the Conference CARI'10, pages 141-148, Yamoussoukro, Ivory
Coast. The preliminary version was also published in the arXiv August 6, 2011
under number arXiv:1108.1478v1. This version was submittted to the journal
ARIMA (January 2011
Cryptanalysis of 4-Pass HAVAL
HAVAL is a cryptographic hash function proposed by Zheng et al. Rompay et al and Wang et al found collisions of full 3-Pass HAVAL. In this paper, we study the security of 4-Pass HAVAL. We find collisions of full versions of 4-Pass HAVAL. The attack is similar to the two-block attack of MD5 proposed by Wang et al. The computational complexity of the attack is about 2^30-2^32 for the first block and 2^27-2^29 for the second block. We use this attack to find 256bit collisions of 4-Pass HAVAL in 3-4 hour on a common PC
Preimage Attacks on 3-Pass HAVAL and Step-Reduced MD5
This paper presents preimage attacks for the hash functions 3-pass
HAVAL and step-reduced MD5. Introduced in 1992 and 1991
respectively, these functions underwent severe collision attacks,
but no preimage attack. We describe two preimage attacks on the
compression function of 3-pass HAVAL. The attacks have a complexity
of about compression function evaluations instead of
. Furthermore, we present several preimage attacks on the
MD5 compression function that invert up to 47 (out of 64) steps
within trials instead of . Though our attacks are
not practical, they show that the security margin of 3-pass HAVAL
and step-reduced MD5 with respect to preimage attacks is not as high
as expected
Preimages for Step-Reduced SHA-2
In this paper, we present a preimage attack for 42 step-reduced SHA-256 with time complexity and memory requirements of order . The same attack also applies to 42 step-reduced SHA-512 with time complexity and memory requirements of order . Our attack is meet-in-the-middle preimage attack
Generic Related-key Attacks for HMAC
In this article we describe new generic distinguishing and forgery attacks in the related-key scenario (using only a single related-key) for the HMAC construction. When HMAC uses a k-bit key, outputs an n-bit MAC, and is instantiated with an l-bit inner iterative hash function processing m-bit message blocks where m=k, our distinguishing-R attack requires about 2^{n/2} queries which improves over the currently best known generic attack complexity 2^{l/2} as soon as l>n. This means that contrary to the general belief, using wide-pipe hash functions as internal primitive will not increase the overall security of HMAC in the related-key model when the key size is equal to the message block size.
We also present generic related-key distinguishing-H, internal state recovery and forgery attacks. Our method is new and elegant, and uses a simple cycle-size detection criterion. The issue in the HMAC construction (not present in the NMAC construction) comes from the non-independence of the two inner hash layers and we provide a simple patch in order to avoid this generic attack. Our work finally shows that the choice of the opad and ipad constants value in HMAC is important
Generic Universal Forgery Attack on Iterative Hash-based MACs
In this article, we study the security of iterative hash-based MACs, such as HMAC or NMAC, with regards to universal forgery attacks. Leveraging recent advances in the analysis of functional graphs built from the iteration of HMAC or NMAC, we exhibit the very first generic universal forgery attack against hash-based MACs. In particular, our work implies that the universal forgery resistance of an n-bit output HMAC construction is not 2^n queries as long believed by the community. The techniques we introduce extend the previous functional graphs-based attacks that only took in account the cycle structure or the collision probability: we show that one can extract much more meaningful secret information by also analyzing the distance of a node from the cycle of its component in the functional graph
NESHA-256, NEw 256-bit Secure Hash Algorithm (Extended Abstract)
In this paper, we introduce a new dedicated 256-bit hash function:
NESHA-256. The recently contest for hash functions held by NIST, motivates us to design the new hash function which has a parallel structure. Advantages of parallel structures and also using some ideas from the designing procedure of block-cipher-based hash functions strengthen our proposed hash function both in security and in efficiency. NESHA-256 is designed not only to have higher security but also to be faster than SHA-256: the performance of NESHA-256 is at least 38% better than that of SHA-256 in software. We give security proofs supporting our design, against existing known cryptographic attacks on hash functions
Cube attacks on cryptographic hash functions
Cryptographic hash functions are a vital part of our current computer sys- tems. They are a core component of digital signatures, message authentica- tion codes, file checksums, and many other protocols and security schemes. Recent attacks against well-established hash functions have led NIST to start an international competition to develop a new hashing standard to be named SHA-3. In this thesis, we provide cryptanalysis of some of the SHA-3 candidates. We do this using a new cryptanalytical technique introduced a few months ago called cube attacks. In addition to summarizing the technique, we build on it by providing a framework for estimating its potential effectiveness for cases too computationally expensive to test. We then show that cube at- tacks can not only be applied to keyed cryptosystems but also to hash func- tions by way of a partial preimage attack. We successfully apply this attack to reduced-round variants of the ESSENCE and Keccak SHA-3 candidates and provide a detailed analysis of how and why the cube attacks succeeded. We also discuss the limits of theoretically extending these attacks to higher rounds. Finally, we provide some preliminary results of applying cube attacks to other SHA-3 candidates
Md5 collisions and the impact on computer forensics
Abstract In August 2004 at the annual cryptography conference in Santa Barbara, California a group of cryptographers, Xianyan Wang, Dengguo Feng, Xuejia Lai, Hongbo Yu, made the announcement that they had successfully generated two files with different contents that had the same MD5 hash. This paper reviews the announcement and discusses the impact this discovery may have on the use of MD5 hash functions for evidence authentication in the field of computer forensics
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