Differential Collisions in SHA-0
CRYPTO '98 Proceedings of the 18th Annual International Cryptology Conference on Advances in Cryptology
Collisions for Step-Reduced SHA-256
Fast Software Encryption
New local collisions for the SHA-2 hash family
ICISC'07 Proceedings of the 10th international conference on Information security and cryptology
Attacking reduced round SHA-256
ACNS'08 Proceedings of the 6th international conference on Applied cryptography and network security
Analysis of step-reduced SHA-256
FSE'06 Proceedings of the 13th international conference on Fast Software Encryption
Efficient collision search attacks on SHA-0
CRYPTO'05 Proceedings of the 25th annual international conference on Advances in Cryptology
Finding collisions in the full SHA-1
CRYPTO'05 Proceedings of the 25th annual international conference on Advances in Cryptology
How to break MD5 and other hash functions
EUROCRYPT'05 Proceedings of the 24th annual international conference on Theory and Applications of Cryptographic Techniques
Deterministic Constructions of 21-Step Collisions for the SHA-2 Hash Family
ISC '08 Proceedings of the 11th international conference on Information Security
New Collision Attacks against Up to 24-Step SHA-2
INDOCRYPT '08 Proceedings of the 9th International Conference on Cryptology in India: Progress in Cryptology
Finding SHA-2 characteristics: searching through a minefield of contradictions
ASIACRYPT'11 Proceedings of the 17th international conference on The Theory and Application of Cryptology and Information Security
Converting meet-in-the-middle preimage attack into pseudo collision attack: application to SHA-2
FSE'12 Proceedings of the 19th international conference on Fast Software Encryption
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Most of the attacks against (reduced) SHA-2 family in literature have used local collisions which are valid for linearized version of SHA-2 hash functions. Recently, at FSE '08, an attack against reduced round SHA-256 was presented by Nikolić and Biryukov which used a local collision which is valid for the actual SHA-256 function. It is a 9-step local collision which starts by introducing a modular difference of 1 in the two messages. It succeeds with probability roughly 1/3. We build on the work of Nikolić and Biryukov and provide a generalized nonlinear local collision which accepts an arbitrary initial message difference. This local collision succeeds with probability 1. Using this local collision we present attacks against 18-step SHA-256 and 18-step SHA-512 with arbitrary initial difference. Both of these attacks succeed with probability 1. We then present special cases of our local collision and show two different differential paths for attacking 20-step SHA-256 and 20-step SHA-512. One of these paths is the same as presented by Nikolić and Biryukov while the other one is a new differential path. Messages following both these differential paths can be found with probability 1. This improves on the previous result where the success probability of 20-step attack was 1/3. Finally, we present two differential paths for 21-step collisions for SHA-256 and SHA-512, one of which is a new path. The success probabilities of these paths for SHA-256 are roughly 2驴 15and 2驴 17which improve on the 21-step attack having probability 2驴 19reported earlier. We show examples of message pairs following all the presented differential paths for up to 21-step collisions in SHA-256. We also show first real examples of colliding message pairs for up to 20-step reduced SHA-512.