Co-organizer of the Crypto In The Clouds Workshop, MIT, August 2009.

Co-organizer of the CPIIS TAU/IDC Workshop on Electronic voting, TAU, May 2009.

Co-organizer of the Theoretical foundations of Practical Information Security workshop, Dagstuhl, December 2008.

Program Committee chair for the Theory of Cryptography Conference (TCC) 2008.

Co-chair of the Multicast Security Working Group at the Internet Engineering Task Force (IETF), 2000-2008.

Co-organizer of the Quantum and Classical Information Security workshop, Caltech, December 2005.

Co-organizer of the Security Analysis of Cryptographic Protocols workshop, DIMACS, June 2004.

Co-organizer of the Cryptographic Protocols in Complex Environments workshop, DIMACS, May 2002.

Program Committee member for Eurocrypt'10, STOC'09, SCN'08, FCC'08, FCC'07, ICALP'07, TCC'07, CSFW'06, FCC'06, FOCS'05, CSFW'05, ACNS'05, TCC'04, SCN'04, FOCS'03, NDSS'03, CRYPTO'01, PODC'01, CRYPTO'00, Eurocrypt 2010.