GnuPG Crypto Library libgcrypt Cracked Via Side-Channel

Keep on Guard!


Some clever boffins including Internet software pioneer djb have gotten libgcrypt cracked via a Side-Channel attack which has to do with the direction of a sliding window carried out in the library.

GnuPG Crypto Library libgcrypt Cracked Via Side-Channel

Patches have already been released so update your Linux servers ASAP, even though honestly it seems like a fairly theoretical attack (this side-channel attack requires that the attacker can run arbitrary software on the hardware where the private RSA key is used) it’s been treated as critical so upgrades are highly recommended.

However, on boxes with virtual machines this attack may be used by oneVM to steal private keys from another VM – which is very common and makes this significantly higher risk.

Linux users need to check out their distributions to see if a nasty bug in libgcrypt20 has been patched.

The patch, which has landed in Debian and Ubuntu, is to address a side-channel attack published last week.

The researchers published their work at the International Association for Cryptologic Research’s e-print archive last week. The paper was authored by Daniel Bernstein, Joachim Breitner, Daniel Genkin, Leon Groot Bruinderink, Nadia Heninger, Tanja Lange, Christine van Vredendaal and Yuval Yarom (who hail variously from the Technical University of Eindhoven, the University of Illinois, the University of Pennsylvania, the University of Maryland, and the University of Adelaide).

What they found is that the libgcrypt library used what’s called “sliding windows”, a method for carrying out the mathematics of cryptography – but one that’s known to leak data.


The technique they are using (which chains together various methodologies) can carry out very efficient full key recovery for RSA-1024.

You can read the full paper here: Sliding right into disaster: Left-to-right sliding windows leak [PDF]

The researchers looked at the left-to-right sliding window calculation in libgcrypt, in which the sliding window data leak was tolerated because it was believed only part of a key was recoverable (40 percent of bits in a four-bit sliding window; 33 percent in a five-bit sliding window).

What they found was an unpleasant surprise: a complete break of the library’s RSA-1024: “We show for the first time that the direction of the encoding matters: the pattern of squarings and multiplications in left-to-right sliding windows leaks significantly more information about the exponent than right-to-left”.

To get at the processing, the researchers also needed to carry out a side-channel attack, specifically a flush+reload cache-timing attack “that monitors the target’s cache access patterns”.

The vulnerability has been assigned a CVE 2017-7526 – and it’s reserved but the details haven’t been published there (I guess they are waiting until the patch is widespread).

Ubuntu Linux 16.04 LTS & 14.04 LTS are both vulnerable as are Debian Linux 6.0 and all Gnupg Libgcrypt versions pretty much 1.7.7 and below.

The GnuPG announcement is here: [Announce] Libgcrypt 1.7.8 released to fix CVE-2017-7526

Source: The Register

Posted in: Cryptography, Exploits/Vulnerabilities


Latest Posts:


Terabytes Of US Military Social Media Spying S3 Data Exposed Terabytes Of US Military Social Media Spying S3 Data Exposed
Once again the old, default Amazon AWS S3 settings are catching people out, the US Military has left terabytes of social media spying S3 data exposed.
SNIFFlab - Create Your Own MITM Test Environment SNIFFlab – Create Your Own MITM Test Environment
SNIFFlab is a set of scripts in Python that enable you to create your own MITM test environment for packet sniffing through a WiFi access point.
Skype Log Viewer Download - View Logs on Windows Skype Log Viewer Download – View Logs on Windows
Skype Log Viewer allows you to download and view the Skype history and log files, on Windows, without actually downloading the Skype client itself.
Ethereum Parity Bug Destroys Over $250 Million In Tokens Ethereum Parity Bug Destroys Over $250 Million In Tokens
If you are into cryptocurrency or blockchain at all, you will have heard about the Ethereum Parity Bug that has basically binned $280 Million + ETH.
WPSeku - Black-Box Remote WordPress Security Scanner WPSeku – Black-Box Remote WordPress Security Scanner
WPSeku is a black box WordPress Security scanner that can be used to scan remote WordPress installations to find security issues and vulnerabilities.
Malaysia Telco Hack - Corporations Spill 46 Million Records Malaysia Telco Hack – Corporations Spill 46 Million Records
The Malaysia Telco Hack has been blowing up in the news with over 42 Million Records being leaked including IMEI numbers, SIM details and home addresses.


Comments are closed.