On Mar 21, 2010, at 4:13 PM, Sergio Lerner wrote: > I looking for a public-key cryptosystem that allows commutation of the > operations of encription/decryption for different users keys > ( Ek(Es(m)) = Es(Ek(m)) ). > I haven't found a simple cryptosystem in Zp or Z/nZ. > > I think the solution may be something like the RSA analogs in elliptic > curves. Maybe a scheme that allows the use of a common modulus for all users > (RSA does not).

If your application can work with a trusted authority generating all the keypairs, and you sacrifice the use of short public exponents *and* sacrifice the possession of the factors of the modulus by the key owners, making them do more work on decryption, I think you can have what you asked for. But that's a lot of ifs. --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to majord...@metzdowd.com