Known as the fastest public key cryptosystem available now

the provable security of NTRU has not been solved well.an encryption padding

called EPN was designed

for NTRU.Under the full domain one wayness assumption of NTRU

EPN had been proved indistinguishable from adaptive chosen ciphertext attack by using the Game-Hopping technology in the random oracle model.Compared with present NAEP available

implement efficiency of EPN improves by 25%.