These are the proceedings of Eurocrypt 2007, the 26th Annual IACR EurocryptConference. The conference was sponsored by the International Association forCryptologic Research (IACR; see www.iacr.org), this year in cooperation withthe Research Group on Mathematics Applied to Cryptography at UPC and theResearch Group on Information Security at UMA. The Eurocrypt 2007 ProgramCommittee (PC) consisted of 24 members whose names are listed on the nextpage.The PC decided on several policies: zero PC papers - no Program Committeemember could submit papers; optional anonymity - authors could choose toanonymize their papers or not. Anonymous papers were treated as usual, i.e.,the author’s identity was not revealed to the PC. The submission software usedwas “Web Submission and Review Software” written and maintained by ShaiHalevi. There were 173 papers submitted to the conference and the PC chose33 of them. Each paper was assigned to at least three PC members, who eitherhandled it themselves or assigned it to an external referee. After the reviews weresubmitted, the committee deliberated both online for several weeks and finallyin a face-to-face meeting held in Paris. In addition to notification of the decisionof the committee, authors received reviews. Our goal was to provide meaningfulcomments to authors of all papers (both those selected for the program andthose not selected). The default for any report given to the committee was thatit should be available to the authors as well.