CECPQ2

In cryptography, Combined Elliptic-Curve and Post-Quantum 2 (CECPQ2) is a quantum secure modification to TLS1.3 developed by Google. It's intended to be used experimentally, to help evaluate the performance of post quantum key-exchange algorithms on actual users’ devices.

Details

Similarly to its predecessor CECPQ1, CECPQ2 aims to provide confidentiality against an attacker with a large scale quantum computer. It is essentially a plugin for the TLS key-agreement part. CECPQ2 combines two key exchange mechanisms: the classical X25519 and HRSS, an instantiation of NTRU, lattice based key exchange primitive.

The algorithm has been deployed on both the server side using Cloudflare’s infrastructure, and the client side using Google Chrome Canary.

CECPQ2 uses 32 bytes of shared secret material derived from the classical X25519 mechanism, and 32 bytes of shared secret material derived from the quantum-secure HRSS mechanism. The resulting bytes are concatenated and used as secret key. Concatenation is meant to assure that the protocol provides at least the same security level as widely used X25519, even if HRSS is found to be insecure.

See also

• TLS
• Elliptic curve Diffie–Hellman
• Quantum cryptography
• NTRU