These are the proceedings of CHES 2004, the 6th Workshop on Cryptographic Hardware and Embedded Systems. For the ?rst time, the CHES Workshop was sponsored by the International Association for Cryptologic Research (IACR). This year, the number of submissions reached a new record. One hundred and twenty-?ve papers were submitted, of which 32 were selected for presen- tion. Each submitted paper was reviewed by at least 3 members of the program committee. We are very grateful to the program committee for their hard and e?cientworkinassemblingtheprogram.Wearealsogratefultothe108external referees who helped in the review process in their area of expertise. In addition to the submitted contributions, the program included three - vited talks, by Neil Gershenfeld (Center for Bits and Atoms, MIT) about "Ph- ical Information Security," by Isaac Chuang (Medialab, MIT) about "Quantum Cryptography," and by Paul Kocher (Cryptography Research) about "Phy- cal Attacks." It also included a rump session, chaired by Christof Paar, which featured informal talks on recent results. Asinthepreviousyears, theworkshopfocusedonallaspectsofcryptographic hardware and embedded system security. We sincerely hope that the CHES Workshop series will remain a premium forum for intellectual exchange in this area.