Cryptology ePrint Archive: Report 2014/599
Post-quantum key exchange for the TLS protocol from the ring learning with errors problem
Joppe W. Bos and Craig Costello and Michael Naehrig and Douglas Stebila
Abstract: Lattice-based cryptographic primitives are believed to offer resilience against attacks by quantum computers. We demonstrate the practicality of post-quantum key exchange by constructing ciphersuites for the Transport Layer Security (TLS) protocol that provide key exchange based on the ring learning with errors (R-LWE) problem; we accompany these ciphersuites with a rigorous proof of security. Our approach ties lattice-based key exchange together with traditional authentication using RSA or elliptic curve digital signatures: the post-quantum key exchange provides forward secrecy against future quantum attackers, while authentication can be provided using RSA keys that are issued by today's commercial certificate authorities, smoothing the path to adoption.
Our cryptographically secure implementation, aimed at the 128-bit security level, reveals that the performance price when switching from non-quantum-safe key exchange is not too high. With our R-LWE ciphersuites integrated into the OpenSSL library and using the Apache web server on a 2-core desktop computer, we could serve 506 RLWE-ECDSA-AES128-GCM-SHA256 HTTPS connections per second for a 10 KiB payload. Compared to elliptic curve Diffie--Hellman, this means an 8 KiB increased handshake size and a reduction in throughput of only 21%. This demonstrates that post-quantum key-exchange can already be considered practical.
Category / Keywords: cryptographic protocols / post-quantum, learning with errors, Transport Layer Security (TLS), key exchange
Date: received 4 Aug 2014, last revised 5 Aug 2014
Contact author: stebila at qut edu au
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Version: 20140805:204432 (All versions of this report)
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