Debian Security Advisory

DLA-1015-1 libgcrypt11 -- LTS security update

Date Reported:
06 Jul 2017
Affected Packages:
Security database references:
In Mitre's CVE dictionary: CVE-2017-7526.
More information:

It was discovered that there was a key disclosure vulnerability in libgcrypt11 a library of cryptographic routines:

It is well known that constant-time implementations of modular exponentiation cannot use sliding windows. However, software libraries such as Libgcrypt, used by GnuPG, continue to use sliding windows. It is widely believed that, even if the complete pattern of squarings and multiplications is observed through a side-channel attack, the number of exponent bits leaked is not sufficient to carry out a full key-recovery attack against RSA. Specifically, 4-bit sliding windows leak only 40% of the bits, and 5-bit sliding windows leak only 33% of the bits.

-- Sliding right into disaster: Left-to-right sliding windows leak

For Debian 7 Wheezy, this issue has been fixed in libgcrypt11 version 1.5.0-5+deb7u6.

We recommend that you upgrade your libgcrypt11 packages.