Post-Quantum Signcryption From Lattice-Based Signatures

In data security, the main objectives one tries to achieve are privacy, data integrity and authentication. In a public-key setting, privacy is reached through asymmetric encryption and both data integrity and authentication through signature. Meeting all the security objectives for data exchange requires to use a concatenation of those primitives in an encryptthen-sign or sign-then-encrypt fashion. Signcryption aims at providing all the security requirements in one single primitive at a lower cost than using encryption and signature together. Most existing signcryption schemes are using ElGamal-based or pairing-based techniques and thus rely on the decisional Diffie-Hellman assumption. With the current growth of a quantum threat, we seek for post-quantum counterparts to a vast majority of publickey primitives. In this work, we propose a signcryption scheme based on the GLP signature inspired from a construction of Malone-Lee. It comes in two flavors, one integrating the usual lattice-based key exchange into GLP and the other merging the signature scheme with a RLWE encryption, which is more efficient, but outputs a larger signcryptext. Using the same set of operations as in existing constructions, our scheme can be implemented efficiently on various platforms, reusing optimized pieces of software or hardware presented in previous works.