Cryptology ePrint Archive: Report 2021/826

OpenSSLNTRU: Faster post-quantum TLS key exchange

Daniel J. Bernstein and Billy Bob Brumley and Ming-Shing Chen and Nicola Tuveri

Abstract: Google's CECPQ1 experiment in 2016 integrated a post-quantum key-exchange algorithm, newhope1024, into TLS 1.2. The Google-Cloudflare CECPQ2 experiment in 2019 integrated a more efficient key-exchange algorithm, ntruhrss701, into TLS 1.3.

This paper revisits the choices made in CECPQ2, and shows how to achieve higher performance for post-quantum key exchange in TLS 1.3 using a higher-security algorithm, sntrup761. Previous work had indicated that ntruhrss701 key generation was much faster than sntrup761 key generation, but this paper makes sntrup761 key generation much faster by generating a batch of keys at once.

Batch key generation is invisible at the TLS protocol layer, but raises software-engineering questions regarding the difficulty of integrating batch key exchange into existing TLS libraries and applications. This paper shows that careful choices of software layers make it easy to integrate fast post-quantum software, including batch key exchange, into TLS with minor changes to TLS libraries and no changes to applications.

As a demonstration of feasibility, this paper reports successful integration of its fast sntrup761 library, via a lightly patched OpenSSL, into an unmodified web browser and an unmodified TLS terminator. This paper also reports TLS 1.3 handshake benchmarks, achieving more TLS 1.3 handshakes per second than any software included in OpenSSL.

Category / Keywords: implementation / applied cryptography, public-key cryptography, NTRU Prime, post-quantum cryptography, TLS, KEM, batch operations, OpenSSL

Original Publication (in the same form): USENIX Security 2022

Date: received 16 Jun 2021, last revised 6 Oct 2021

Contact author: authorcontact-opensslntru at box cr yp to

Available format(s): PDF | BibTeX Citation

Note: 18 pages, 5 figures; accepted at USENIX Security 2022; reduced number of pages compressing appendices into main body and editing figures, reorganized some content into a revised "Related works" section and comparison table in Background to improve comparison of our contributions with existing works

Version: 20211006:163417 (All versions of this report)

Short URL:

[ Cryptology ePrint archive ]