Jan Camenisch Aggelos Kiayias Moti Yung On the Portability of Generalized Schnorr Proofs. 425-442 2009 EUROCRYPT http://dx.doi.org/10.1007/978-3-642-01001-9_25 conf/eurocrypt/2009 db/conf/eurocrypt/eurocrypt2009.html#CamenischKY09