The RSA Conferenceis attended by over10,000securityprofessionalseach year. The Cryptographers' Track (CT-RSA), one of several parallel tracks at the c- ference, provides an excellent opportunity for cryptographers to showcase their research to a wide audience. CT-RSA 2005 was the ?fth year of the Cryptog- phers' Track. The selection process for the CT-RSA program is the same as for other cryptography research conferences. This year, the program committee selected 23 papers from 74submissions (two of whichwerelater withdrawn) that covered all aspects of cryptography. The program also included two invited talks by Cynthia Dwork and Moti Yung. These proceedings contain the revised versions of the selected papers. The revisions were not checked, and so the authors (and not the committee) bear full responsibility for the contents of their papers. I am very grateful to the program committee for their very conscientious e?orts to review each paper fairly and thoroughly. The initial review stage was followed by a tremendous amount of discussion which contributed to our high con?denceinour judgements.Thanks alsoto the manyexternalreviewerswhose names arelisted in the followingpages.My apologiesto thosewhose nameswere inadvertently omitted from this list. Thanks to Eddie Ng for maintaining the submission server and the Web reviewsystem.ThesubmissionsoftwarewaswrittenbyChanathipNamprempre, and the Web review software by Wim Moreau and Joris Claessens. Thanks to AlfredHofmannandhiscolleaguesatSpringerforthetimelyproductionofthese proceedings.Finally, it is my pleasureto acknowledgeAri Juels and MikeSzydlo of RSA Laboratories for their assistance and cooperation during the past seven months.