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 Finding Collisions in the Full SHA-1. The conference program included two invited lectures. Ralph Merkle del- ered an IACR Distinguished Lecture entitled The Development of Public Key Cryptography: a PersonalView; and Thoughts on Nanotechnology. Dan Boneh gave an invited talk entitled Bilinear Maps in Cryptography. We continued the tradition of a rump session featuring short informal presentations (usually serious sometimes entertaining and occasionally both). ~ The rump session was chaired this year by Phong Q. Nguy^ en.