Collisions and other Non-Random Properties for Step-Reduced SHA-256. Cryptology eprint Archive, April 2008. Available at http://eprint.iacr

Abstract. We study the security of step-reduced but otherwise unmodified SHA-256. We show the first collision attacks on SHA-256 reduced to 23 and 24 steps with complexities 2 18 and 2 28.5, respectively. We give example colliding message pairs for 23-step and 24-step SHA-256. The best previous, recently obtained result was a collision attack for up to 22 steps. We extend our attacks to 23 and 24-step reduced SHA-512 with respective complexities of 2 44.9 and 2 53.0. Additionally, we show nonrandom behaviour of the SHA-256 compression function in the form of free-start near-collisions for up to 31 steps, which is 6 more steps than the recently obtained non-random behaviour in the form of a free-start near-collision. Even though this represents a step forwards in terms of cryptanalytic techniques, the results do not threaten the security of applications using SHA-256. Keywords: SHA-256, SHA-512, hash functions, collisions, semi-freestart collisions, free-start collisions, free-start near-collisions

Book Review: Austin, Cleared for Takeoff: Aviators, Businessmen, and the Growth of an American City

At its widest point, Texas measures some 850 miles across. EI Paso, in the extreme west, is closer to Los Angeles than it is to Texarkana, sited near the state\u27s eastern boundary. Given the distances its citizens have to travel, Texas has always been attuned to transport technology. And people living in the capital, Austin, near the state\u27s center, have always been interested in finding rapid forms of travel to the far-flung cities and counties of the rest of the state. Thus, Ragsdale\u27s book touches on a highly relevant aspect of urban as well as regional history. Moreover, as national and international travel became accepted for business as well as pleasure, the role of airlines and airports serving Austin took on a growing immediacy

Boomerang Attack on Step-Reduced SHA-512

function family issued by the National Institute of Standards and Tech-nology (NIST) in 2002 and is widely used all over the world. In this work, we analyze the security of SHA-512 with respect to boomerang attack. Boomerang distinguisher on SHA-512 compression function reduced to 48 steps is proposed, with a practical complexity of 251. A practical ex-ample of the distinguisher for 48-step SHA-512 is also given. As far as we know, it is the best practical attack on step-reduced SHA-512. Key words: SHA-512, hash functions, boomerang attack.