These are the proceedings of Crypto 2005, the 25th Annual International Cr- tology Conference. The conference was sponsored by the International Assoc- tion for Cryptologic Research (IACR) in cooperation with the IEEE Computer ScienceTechnicalCommitteeonSecurityandPrivacyandtheComputerScience DepartmentoftheUniversityofCaliforniaatSantaBarbara. Theconferencewas held in Santa Barbara, California, August 14¿18, 2005. Theconferencereceived178submissions,outofwhichtheprogramcommittee selected33forpresentation. Theselectionprocesswascarriedoutbytheprogram committee via an ¿online¿ meeting. The authors of selected papers had a few weeks to prepare ?nal versions of their papers, aided by comments from the reviewers. However, most of these revisions were not subject to any editorial review. This year, a ¿Best Paper Award¿ was given to Xiaoyun Wang, Yiqun Lisa Yin, and Hongbo Yu, for their paper