"Make sure DSA signing exponentiations really are constant-time"

Cesar Pereida García, Billy Bob Brumley, Yuval Yarom

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review

47 Citations (Scopus)
40 Downloads (Pure)


TLS and SSH are two of the most commonly used protocols for securing Internet traffic. Many of the implementations of these protocols rely on the cryptographic primitives provided in the OpenSSL library. In this work we disclose a vulnerability in OpenSSL, affecting all versions and forks (e.g. LibreSSL and BoringSSL) since roughly October 2005, which renders the implementation of the DSA signature scheme vulnerable to cache-based side-channel attacks. Exploiting the software defect, we demonstrate the first published cache-based key-recovery attack on these protocols: 260 SSH-2 handshakes to extract a 1024/160-bit DSA host key from an OpenSSH server, and 580 TLS 1.2 handshakes to extract a 2048/256-bit DSA key from an stunnel server.

Original languageEnglish
Title of host publicationCCS 2016 - Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security
Number of pages12
ISBN (Electronic)9781450341394
Publication statusPublished - 24 Oct 2016
MoE publication typeA4 Article in a conference publication
EventACM Conference on Computer and Communications Security - Hofburg Palace, Vienna, Austria
Duration: 24 Oct 201628 Oct 2016
Conference number: 23


ConferenceACM Conference on Computer and Communications Security
Abbreviated titleCCS
Internet address


  • Applied cryptography
  • Cache-timing attacks
  • CVE-2016-2178
  • Digital signatures
  • DSA
  • OpenSSL
  • Side-channel analysis
  • Timing attacks


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