React: Rapid enhanced-security asymmetric cryptosystem transform

Abstract

Seven years after the optimal asymmetric encryption pad-ding (OAEP) which makes chosen-ciphertext secure encryption scheme from any trapdoor one-way permutation (but whose unique application is RSA), this paper presents REACT, a new conversion which applies to any weakly secure cryptosystem, in the random oracle model: it is optimal from both the computational and the security points of view. Indeed, the overload is negligible, since it just consists of two more has-hings for both encryption and decryption, and the reduction is very tight. Furthermore, advantages of REACT beyond OAEP are numerous: 1. it is more general since it applies to any partially trapdoor one-way function (a. k. a. weakly secure public-key encryption scheme) and therefore provides security relative to RSA but also to the Diffe-Hellman problem or the factorization; 2. it is possible to integrate symmetric encryption (block and stream ciphers) to reach very high speed rates; 3. it provides a key distribution with session key encryption, whose overall scheme achieves chosen-ciphertext security even with weakly secure symmetric scheme. Therefore, REACT could become a new alternative to OAEP, and even reach security relative to factorization, while allowing symmetric integration.