PKC2004wasthe7thInternationalWorkshoponPracticeandTheoryinPublic Key Cryptography and was sponsored by IACR, the International Association for Cryptologic Research (www. iacr. org). This year the workshop was organized 2 in cooperation with the Institute for Infocomm Research (I R), Singapore. There were 106 paper submissions from 19 countries to PKC 2004. That is the highest submission number in PKC history. Due to the large number of submissionsandthehighqualityofthe submittedpapers,notallthepapersthat contained new ideas were accepted. Of the 106 submissions, 32 were selected for the proceedings. Each paper was sent to at least 3 members of the Program Committee for comments. The revised versions of the accepted papers were not checked for correctness of their scienti?c aspects and the authors bear the full responsibility for the contents of their papers. Some authors will write ?nal versions of their papers for publication in refereed journals. I am very grateful to the members of the Program Committee for their hard work in the di?cult task of selecting fewer than 1 in 3 of the submitted papers, as well as the following external referees who helped the Program Committee: Nuttapong Attrapadung,RobertoMariaAvanzi,GildasAvoine,JoonsangBaek, Qingjun Cai, Jae Choon Cha, Chien-Ning Chen, Liqun Chen, Xiaofeng Chen, Koji Chida, Nicolas T.
Courtois, Yang Cui, Jean-Franco , is Dhem, Louis Goubin, Louis Granboulan, Rob Granger, Jens Groth, Yumiko Hanaoka, Darrel Hank- son,Chao-ChihHsu,TetsutaroKobayashi,YuichiKomano,HidenoriKuwakado, TanjaLange,PeterLeadbitter,ByoungcheonLee,Chun-KoLee,HenryC. J. Lee, JohnMaloneLee,YongLi,Beno ?tLibert,Hsi-ChungLin,YiLu,JeanMonnerat, Anderson C. A. Nascimento, C.