Signed (Group) Diffie–Hellman Key Exchange with Tight Security

Abstract We propose the first tight security proof for ordinary two-message signed Diffie–Hellman key exchange protocol in random oracle model. Our is based on strong computational assumption and multiuser of a digital signature scheme. With our proof, DH can be deployed with optimal parameters, independent number users or sessions, without need to compensate any loss. abstract approach new notion called verifiable exchange. In contrast known three-message variant (Gjøsteen Jager, in: Shacham, Boldyreva (eds) CRYPTO 2018, Part II. LNCS, Springer, Heidelberg, 2018), we do not require modification original protocol, tightness result proven “Single-Bit-Guess” model which know tightly composed symmetric cryptographic primitives establish secure channel. Finally, extend group setting construct authenticated protocol.