We first introduce some basic problems in lattice-based cryptography. Then we show how multibit LWE-based cryptosystem and IBE system can be constructed on them. According to the method put forward by D. Boneh et. al., we construct a public key cryptosystem from the IBE system. The cryptosystem is CCA-secure.
At present, most of the identity based encryption (IBE) schemes from the lattice originate from the results of Gentry et.al., and regard each identity as a bit string with equal length and then map a matrix to every bit of identity string. Consequently, they are considerably less efficient. In our paper, we construct an IBE which is efficient from standard learning with errors problem and handles identities as a chunk for performance. In the standard model, our paper gives a proof which our IBE is IND-sID-CCA secure. Mean-while, we also show which our IBE construction is also IND-ID-CCA secure via the technique i.e., imposing additional restrictions on the identities, presented by Boyen and Boneh.
Among the different cryptosystems, the Public Key Cryptosystems (PKCS) are of great usage and are used in many applications. Most of the current PKCS are based on a hard problem making the cryptanalysis of such cipher infeasible given the current computing and memory availability. However, Quantum Computing threatens all the current PKCS as they offer a new model that can solve those hard problems, e.g. the factorization problem of RSA or the discrete logarithm problem of ELGAMAL algorithm. Lattice Based PKCS are a promising filed to introduce an immune cipher system against quantum cryptanalysis. This paper presents a summary of recent progress in the field of lattice-based cryptography, by focusing on the recent advancement in lattice-based public key cryptosystems and key exchange mechanisms based on the learning with errors (LWE) problem and its ring variant Ring-LWE.
The standard public-key cryptosystems used today relies mathematical problems that require a lot of computing force to solve, so much that, with the right parameters, they are computationally unsolvable. But there are quantum algorithms that are able to solve these problems in much shorter time. These quantum algorithms have been known for many years, but have only been a problem in theory because of the lack of quantum computers. But with recent development in the building of quantum computers, the cryptographic world is looking for quantum-resistant replacements for today’s standard public-key cryptosystems. Public-key cryptosystems based on lattices are possible replacements. This thesis presents several possible candidates for new standard public-key cryptosystems, mainly NTRU and ring-LWE-based systems. The latticebased cryptosystems are shown to be very fast and have strong, provable security against quantum computers, but are a lot more complicated than RSA and Diffie-Hellman.
This chapter introduces post-quantum cryptography. It describes lattice-based cryptographic constructions of post-quantum cryptography. Lattice-based cryptographic constructions are one of candidates of post-quantum cryptography, which are believed to be secure against quantum computers. Learning with errors (LWE) is one of the most promising primitives in many usages due to its lightweight operation and rigorous security reduction against the worst-case of the lattice problems that are considered to be hard to solve even after the advance of quantum computers. After the research about the connection between the LWE problem and some lattice problems, some variants of LWE, of which the secret distributions are modified from the uniform distribution, were proposed. Due to the efficiency and compactness of ring-LWE, many lattice-based cryptosystems are constructed as ring-LWE based, rather than LWE-based. The chapter explains a ring variant of Lizard scheme, called RLizard, IND-CCA secure encryption scheme.
An improved method of generating trapdoor on ideal lattice was proposed by a stronger regularity bound theorem,then with R-LWE encryption algorithm and strongly unforgeable one-time signature tool from ideal lattice,an adaptive chosen-ciphertext attack(CCA) secure PKE scheme under the standard model was designed.The new PKE scheme supported public ciphertext integrity verification,could achieve block encryption and had a high encryption/decryption speed and a low encryption blowup factor,whose security proved reduced to decisional R-LWE assumption tightly.The construction is the first CCA-secure PKE cryptosystem completely based on hard problems from ideal lattice.