Visible to the public "Make Sure DSA Signing Exponentiations Really Are Constant-Time"

Title"Make Sure DSA Signing Exponentiations Really Are Constant-Time"
Publication TypeConference Paper
Year of Publication2016
AuthorsPereida García, Cesar, Brumley, Billy Bob, Yarom, Yuval
Conference NameProceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security
Date PublishedOctober 2016
Conference LocationNew York, NY, USA
ISBN Number978-1-4503-4139-4
KeywordsApplied Cryptography, cache-timing attacks, CVE-2016-2178, digital signatures, DSA, exponentiation, Human Behavior, Kerberos, Metrics, OpenSSL, pubcrawl, Resiliency, side-channel analysis, timing attacks

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.

Citation Keypereida_garcia_make_2016