Elliptic curve cryptosystems have the smallest ciphertexts among the ones commonly used. But if you want a 128-bit ciphertext, you'll only have about 2^64 security with an elliptic curve cryptosystem. Look in oids.h and search for "elliptic" for the name of some 128-bit curves.
On Wed, Mar 19, 2003 at 11:37:16AM +0100, Hans M?ller wrote: > Hello > > > > Does it exist a private / public key algorithm that can generate smaller messages > than 512 bits. > > > > I need this for a challenge / response algorithm. The challenge code will be the > encrypted with a > > private key (on a web server) and the encrypted challenge code will be the response > code. > > > > The user will enter the response code (in the software) and the software will > decrypt the response > > code with the public key. > > > > The problem is that haven found any public / private algorithms that generate > smaller encrypted > > messages than 512 bits. And the user must be able to enter the response code in the > software > > and this demands that the generated message (response code) must be less that 128 > bits. > > > > Best regards > > Hans M?ller
