Electrical Engenieering Department
Oral Defense Notice | 396 |
Analysis and designing of Cryptographic Hash Functions |
In this thesis we conceder the designing and analysis of cryptographic hash functions. Our analysis leads to variety of successful attacks for the known hash functions, includes: ¨ multicollision attack on ZIPPER HASH, SFRH, and MFRH ¨ Collision, preimage and second preimage on CRUSH.In addition, we study the relationship between information theoretic attack costs and real costs. We show that in the information theoretic model, many well-known and commonly used hash functions such as MD5 and SHA-256 fail to be preimage resistant. We propose a generic n -bit iterated hash function framework based on n -bit compression function called Suffix-free-Prefix-free (SFPF) which works for arbitrary IV s and does not possess MD strengthening. We formally prove that SFPF is indifferentiable from the random oracle (RO) when the compression function is viewed as a fixed input-length random oracle (FIL-RO). We also design a concrete hash constriction which fits the SFPF. A hash function with free IV has many benefits such as speedup for the short messages up to two times and applications in randomized hashing. We propose a permutation based compression function and prove its security with respect to collision and (second) preimage attacks in the ideal permutation model. The proposed compression function can be seen as a generalization of the compression function of MD6 hash function. |
By: Nasour BAgheri Supervisor: Dr. Majid Naderi Advisor: Dr Babak Sadeghiyan Referees : Dr. Taba Taba Vakioli, Dr. Beheshti Shirazi, Dr. Shahossaini, Dr. Ahmadian, Dr. Eghlidos |
Date: Monday July 12, 2010 Time: 5:00PM Location: The seminar room of E.E. Dept |