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Lecture Notes in Computer Science
In this paper, we analyze the collision resistance of SHA-2 and provide the first results since the beginning of the NIST SHA-3 competition. We extend the previously best known semi-free-start collisions on SHA-256 from 24 to 32 (out of 64) steps and show a collision attack for 27 steps. All our attacks are practical and verified by colliding message pairs. We present the first automated tool for finding complex differential characteristics in SHA-2 and show that the techniques on SHA-1 cannotdoi:10.1007/978-3-642-25385-0_16 fatcat:kavmn7qsurd6fjxan3bkesh72a