Cryptography as we are used to has two big cathegories of ciphers: public key ciphers (asymmetric), and private key ciphers (symmetric).
Sysepub is the implementation of a new system, which wants to combine the power of One Time Pad with the advantages of public key ciphers. It uses a symmetric algorithm (XOR), but it uses two keys: one is private and the other is public.
See how it works.
Note: Sysepub is NOT a well known and established cipher, but rather a proposal. If you want, read a public discussion about it, that took place on the Usenet (September 2002). Please note also that Sysepub comes with the GNU GPL license, then WITHOUT ANY WARRANTY of any kind.