Multi-party Key Exchange for Unbounded Parties from Indistinguishability Obfuscation.

Existing protocols for non-interactive multi-party key exchange either 1 support a bounded number of users, 2 require a trusted setup, or 3 rely on knowledge-type assumptions. We construct the first non-interactive key exchange protocols which support an unbounded number of parties and have a security proof that does not rely on knowledge assumptions. Our non-interactive key-exchange protocol does not require a trusted setup and extends easily to the identity-based setting. Our protocols suffer only a polynomial loss to the underlying hardness assumptions.