[Announce] [security fix] GnuPG 1.4.16 released
wk at gnupg.org
Wed Dec 18 15:05:38 CET 2013
Along with the publication of an interesting new side channel attack by
Daniel Genkin, Adi Shamir, and Eran Tromer we announce the availability
of a new stable GnuPG release to relieve this bug: Version 1.4.16.
This is a *security fix* release and all users of GnuPG versions 1.x are
advised to updated to this version. GnuPG versions 2.x are not
affected. See below for the impact of the problem.
The GNU Privacy Guard (GnuPG) is GNU's tool for secure communication
and data storage. It is a complete and free replacement of PGP and
can be used to encrypt data and to create digital signatures. It
includes an advanced key management facility, smartcard support and is
compliant with the OpenPGP Internet standard as described by RFC-4880.
Note that this version is from the GnuPG-1 series and thus smaller than
those from the GnuPG-2 series, easier to build, and also better portable
to ancient platforms. In contrast to GnuPG-2 (e.g version 2.0.22) it
comes with no support for S/MIME, Secure Shell, or other tools useful
for desktop environments. Fortunately you may install both versions
alongside on the same system without any conflict.
* Fixed the RSA Key Extraction via Low-Bandwidth Acoustic
Cryptanalysis attack as described by Genkin, Shamir, and Tromer.
See <http://www.cs.tau.ac.il/~tromer/acoustic/>. [CVE-2013-4576]
* Put only the major version number by default into armored output.
* Do not create a trustdb file if --trust-model=always is used.
* Print the keyid for key packets with --list-packets.
* Changed modular exponentiation algorithm to recover from a small
performance loss due to a change in 1.4.14.
Impact of the security problem
CVE-2013-4576 has been assigned to this security bug.
The paper describes two attacks. The first attack allows to distinguish
keys: An attacker is able to notice which key is currently used for
decryption. This is in general not a problem but may be used to reveal
the information that a message, encrypted to a commonly not used key,
has been received by the targeted machine. We do not have a software
solution to mitigate this attack.
The second attack is more serious. It is an adaptive chosen ciphertext
attack to reveal the private key. A possible scenario is that the
attacker places a sensor (for example a standard smartphone) in the
vicinity of the targeted machine. That machine is assumed to do
unattended RSA decryption of received mails, for example by using a mail
client which speeds up browsing by opportunistically decrypting mails
expected to be read soon. While listening to the acoustic emanations of
the targeted machine, the smartphone will send new encrypted messages to
that machine and re-construct the private key bit by bit. A 4096 bit
RSA key used on a laptop can be revealed within an hour.
GnuPG 1.4.16 avoids this attack by employing RSA blinding during
decryption. GnuPG 2.x and current Gpg4win versions make use of
Libgcrypt which employs RSA blinding anyway and are thus not vulnerable.
For the highly interesting research on acoustic cryptanalysis and the
details of the attack see http://www.cs.tau.ac.il/~tromer/acoustic/ .
Getting the Software
First of all, decide whether you really need GnuPG version 1.4.x - most
users are better off with the modern GnuPG 2.0.x version. Then follow
the instructions found at http://www.gnupg.org/download/ or read on:
GnuPG 1.4.16 may be downloaded from one of the GnuPG mirror sites or
direct from ftp://ftp.gnupg.org/gcrypt/ . The list of mirrors can be
found at http://www.gnupg.org/mirrors.html . Note, that GnuPG is not
available at ftp.gnu.org.
On the mirrors you should find the following files in the *gnupg*
GnuPG source compressed using BZIP2 and OpenPGP signature.
GnuPG source compressed using GZIP and OpenPGP signature.
A patch file to upgrade a 1.4.15 GnuPG source tree. This patch
does not include updates of the language files.
Select one of them. To shorten the download time, you probably want to
get the BZIP2 compressed file. Please try another mirror if exceptional
your mirror is not yet up to date.
In the *binary* directory, you should find these files:
GnuPG compiled for Microsoft Windows and its OpenPGP signature.
This is a command line only version; the source files are the same
as given above. Note, that this is a minimal installer and unless
you are just in need for the gpg binary, you are better off using
the full featured installer at http://www.gpg4win.org . Gpg4win
uses GnuPG 2.x and is thus not affected by the security bug.
Checking the Integrity
In order to check that the version of GnuPG which you are going to
install is an original and unmodified one, you can do it in one of
the following ways:
* If you already have a trusted version of GnuPG installed, you
can simply check the supplied signature. For example to check the
signature of the file gnupg-1.4.16.tar.bz2 you would use this command:
gpg --verify gnupg-1.4.16.tar.bz2.sig
This checks whether the signature file matches the source file.
You should see a message indicating that the signature is good and
made by that signing key. Make sure that you have the right key,
either by checking the fingerprint of that key with other sources
or by checking that the key has been signed by a trustworthy other
key. Note, that you can retrieve the signing key using the command
finger wk ,at' g10code.com | gpg --import
or using a keyserver like
gpg --recv-key 4F25E3B6
The distribution key 4F25E3B6 is signed by the well known key
1E42B367. If you get an key expired message, you should retrieve a
fresh copy as the expiration date might have been prolonged.
NEVER USE A GNUPG VERSION YOU JUST DOWNLOADED TO CHECK THE
INTEGRITY OF THE SOURCE - USE AN EXISTING GNUPG INSTALLATION!
* If you are not able to use an old version of GnuPG, you have to verify
the SHA-1 checksum. Assuming you downloaded the file
gnupg-1.4.16.tar.bz2, you would run the sha1sum command like this:
and check that the output matches the first line from the
GnuPG comes with support for 29 languages. The Chinese (Simple and
Traditional), Czech, Danish, Dutch, French, German, Norwegian, Polish,
Romanian, Russian, Spanish, Swedish, Ukrainian, and Turkish translations
are close to be complete.
A listing with commercial support offers for GnuPG is available at:
The driving force behind the development of GnuPG is the company of its
principal author, Werner Koch. Maintenance and improvement of GnuPG and
related software take up a most of their resources. To allow them
continue their work they ask to either purchase a support contract,
engage them for custom enhancements, or to donate money:
We have to thank all the people who helped with this release, be it
testing, coding, translating, suggesting, auditing, donating money,
spreading the word, or answering questions on the mailing lists. Many
thanks to Eran Tromer for providing early drafts of the paper and
testing the fixes.
The GnuPG Team
Die Gedanken sind frei. Ausnahmen regelt ein Bundesgesetz.
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