id: 01771670 dt: j an: 01771670 au: Biham, Eli; Boneh, Dan; Reingold, Omer ti: Breaking generalized Diffie-Hellman modulo a composite is no easier than factoring. so: Inf. Process. Lett. 70, No.2, 83-87 (1999). py: 1999 pu: Elsevier Sciences Publishers (North-Holland), Amsterdam la: EN cc: ut: generalized Diffie-Hellman assumption; factorization algorithm; Blum integers ci: Zbl 0922.68052 li: doi:10.1016/S0020-0190(99)00047-2 ab: Summary: The Diffie-Hellman key-exchange protocol may naturally be extended to $k>2$ parties. This gives rise to the generalized Diffie-Hellman assumption (GDH-assumption). {\it M. Naor} and {\it O. Reingold} [J. Comput. Syst. Sci. 58, 336-375 (1999; Zbl 0922.68052)] have recently shown an efficient construction of pseudo-random functions and proved its security based on the GDH-assumption. In this note, we prove that breaking this assumption modulo a so-called Blum integer would imply an efficient algorithm for factorization. Therefore, both the key-exchange protocol and the pseudo-random functions are secure as long as factoring Blum integers is hard. Our reduction strengthens a previous “worst-case" reduction of Shmuely (1985). rv: