A novel CPA-secure hybrid encryption scheme based-on pNE cryptosystem

Although pNE is a new and unique provably secure variant of famous NTRU cryptosystem so far, the message-expansion factor of pNE, similar to other variants of NTRU, is rather larger than that of other traditional public-key cryptosystems. In this paper, beside introducing RISKE, a new probabilistic secret-key cryptosystem based-on characteristics of invertible elements in binary truncated quotient polynomial rings, we combine it with pNE to construct a novel hybrid cryptosystem, named HpNE, which not only is IND-CPA secure but also has smaller message-expansion factor than pNE does.