A Modified RSA Cryptosystem with DHKEP-Derived Session Keys
Hayder R. Hashim · Lobachevskii Journal of Mathematics · 2026
Abstract This paper focuses on a proposed novel modification to the classical RSA cryptosystem by deriving the encryption key dynamically from a shared secret established by the Diffie–Hellman Key Exchange Protocol (DHKEP) adopted by communicating parties. Moreover, the decryption key is also computed secretly by the same communicating parties, and it represents the inverse the encryption key modulo a large positive integer, a product of two primes. This approach enhances key flexibility since the keys generated differently in each session mitigates attacks targeting public keys. The proposed cryptosystem preserves RSA’s security, that is represented by the Integer Factorization Problem (IFP) while incorporating the security strengths of the Discrete Logarithm Problem (DLP).