Debian 7: DLA-1015-1 Critical Key Exposure in Libgcrypt11 Cryptography

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.


Regards,

- --
,'`.
: :' : Chris Lamb
`. `'` lamby@debian.org / chris-lamb.co.uk
`-