Eurocrypt 2015, the 34th annual International Conference on the Theory and Applications of Cryptographic Techniques, was held April 26-30, 2015, in Sofia, Bulgaria, and sponsored by the International Association for Cryptologic Research (IACR). Responsible for the local organization were Svetla Nikova, from the KU Leuven, and Dimitar Jetchev, from the EPFL. They were supported by a local organizing committee consisting of Tsonka Baicheva (Institute of Mathematics and Informatics, BAS), Violeta Ducheva (SANS), Georgi Sharkov (ESI Center Eastern Europe). We are indebted to them for their support.

To accommodate the request by IACR to showcase as many high-quality submissions as possible, the programme was organised in two tracks. These tracks ran in parallel with the exception of invited talks, the single best paper, and two papers with honorable mention. Following a popular convention in contemporary cryptography, one track was labelled R and featured results more closely related to "real" world cryptography, whereas the second track was labelled I and featured results in a more abstract or "ideal" world.

A total of 194 submissions were considered during the review process, many were of high-quality. As usual, all reviews were conducted double-blind and we excluded Program Committee members from discussing submissions for which they had a possible conflict of interest. To account for a desire (by authors and the wider community alike) to maintain the high standard of publications, we allowed for longer submissions such that essential elements of proofs or other form of evidence could be included in the body of the submissions. Furthermore, a more focused review process was used that consisted of two rounds. In the first round of reviews we solicited three independent reviews per submission. After a short discussion phase among the 38 Program Committee members, just over half of the submissions were retained for the second round. Authors of these retained papers were given the opportunity to comment on the reviews so far. After extensive deliberations in a second round, we accepted 57 papers. The revised versions of these papers are included in these two volume proceedings, organised topically within their respective track.

The review process would have been impossible without the hard work of the Program Committee members and over 210 external reviewers, whose effort we would like to commend here. It has been an honor to work with everyone. The process was enabled by the Web Submission and Review Software written by Shai Halevi and the server was hosted by IACR. We would like to thank Shai for setting up the service on the server and helping us whenever needed.

The Program Committee decided to honor one submission with the Best Paper Award this year. This submission was "Cryptanalysis of the Multilinear Map over the Integers" authored by Junghee Cheo, Kyoohyung Han, Changmin Lee, Hansol Ryu and Damien Stehlé. The two runners-up to the award, "Robust Authenticated-Encryption: AEZ and the Problem that it Solves" (by Viet Tung Hoang, Ted Krovetz, and Phillip Rogaway) and "On the behaviors of affine equivalent Sboxes regarding differential and linear attacks" (by Anne Canteaut and Joëlle Roué) received Honorable Mentions and hence invitations for the Journal of Cryptology.

In addition to the contributed talks, we had three invited speakers: Kristin Lauter, Tal Rabin, and Vincent Rijmen. We would like to thank them for accepting our invitation and thank everyone (speakers, session chairs, and rump session chair) for their contribution to the program of Eurocrypt 2015.

Elizabeth Oswald
Marc Fischlin
Eurocrypt 2015 Program Chairs