NTRU is an asymmetric (public/private key) cryptosystem. It has two characteristics that make it interesting as an alternative to RSA and Elliptic Curve Cryptography: speed and quantum computing resistance. There are two NTRU based algorithms: NTRUEncrypt and NTRUSign. An open source implementation of NTRU is available.
Read more about NTRU: Speed, Resistance To Quantum-computer-based Attacks, Standardization, Implementations, History