CCA-Secure Cryptosystem from Lattice
We propose a simple construction of CCA- secure publickey encryption scheme based on lattice in the standard model. Our construction regards lattice-based cryptosystem mR05 of , which is the multi-bit version of single-bit cryptosystems R05 , as building block and makes use of its indistinguishable pseudohomomorphism property which is known to be achievable without random oracles and which is the crux that we can construct a public key encryption scheme which is CCA-secure in standard model. This makes our construction approach quite dierent from existing ones. So far as we know, our construction is the rst CCA-secure cryptosystem which is directly constructed from lattice and whose security is directly based on the standard lattice problem which is hard in the worst case for quantum algorithms.