Off-the-Record (OTR) Messaging allows you to have private conversations
over instant messaging by providing:
- No one else can read your instant messages.
- You are assured the correspondent is who you think it is.
- The messages you send do not have digital signatures that are
checkable by a third party. Anyone can forge messages after a
conversation to make them look like they came from you. However,
during a conversation, your correspondent is assured the messages
he sees are authentic and unmodified.
- Perfect forward secrecy
- If you lose control of your private keys, no previous conversation is compromised.
9 Mar 2016
- Security update: libotr version 4.1.1
Versions 4.1.0 and earlier of libotr in 64-bit builds contain an integer
overflow security flaw. This flaw could potentially be exploited by a
remote attacker to cause a heap buffer overflow and subsequently for
arbitrary code to be executed on the user's machine.
CVE-2016-2851 has been assigned to this issue.
Please upgrade to libotr version 4.1.1 immediately.
Users of libotr packages in Linux and *BSD distributions should see updated packages shortly.
This security release includes the following updates:
- Fix an integer overflow bug that can cause a heap buffer overflow (and
from there remote code execution) on 64-bit platforms
- Fix possible free() of an uninitialized pointer
- Be stricter about parsing v3 fragments
- Add a testsuite ("make check" to run it), but only on Linux for now,
since it uses Linux-specific features such as epoll
- Fix a memory leak when reading a malformed instance tag file
- Protocol documentation clarifications
- pidgin-otr version 4.0.2 released
This point release includes the following updates:
- Fix use-after-free issue during SMP
- Updated Spanish, German, Norwegian Bokmål translations
- New Danish translation
- The Windows binary has been linked with updated versions of libotr, libgcrypt, libgpg-error, and other supporting libraries
OTR library and toolkit
This is the portable OTR Messaging Library, as well as the toolkit to
help you forge messages. You need this library in order to use the other
OTR software on this page. [Note that some binary packages, particularly
Windows, do not have a separate library package, but just include the library
and toolkit in the packages below.] The current version is 4.1.1.
UPGRADING from version 3.2.x
- Source code (4.1.1)
- Compressed tarball
Java OTR library
This is the Java version of the OTR library. This is for developers of Java applications that want to add support for OTR. End users do not require this package. It's still early days, but you can download java-otr version 0.1.0 (sig).
OTR localhost AIM proxy
This software is no longer supported. Please use an IM client with native support for OTR.
This is a localhost proxy you can use with almost any AIM client in order
to participate in Off-the-Record conversations. The current version is
0.3.1, which means it's still a long way from done. Read the README
file carefully. Some things it's still missing:
- Username/password authentication to the proxy
- Having the proxy be able to use outgoing proxies itself
- Support for protocols other than AIM/ICQ
- Configurability of the proxy types and ports it uses
But it should work for most people. Please send feedback to the
otr-users mailing list
, or to the dev team
You may need the above library packages.
- Source code (0.3.1)
- Compressed tarball
- Windows (0.3.1)
- Win32 installer
- OS X (0.3.1)
- OS X package
If you use OTR software, you should join at least the otr-announce
mailing list, and possibly otr-users
(for users of OTR software) or otr-dev (for developers of OTR software) as well.
- What implementations of Off-the-Record Messaging are there?
- Please see our OTR-enabled software page.
The OTR functionality is separated into the
Off-the-Record Messaging Library (libotr), which is an LGPL-licensed
library that can be used to (hopefully) easily produce OTR plugins for
other IM software, or for other applications entirely.
- What is the license for the OTR software?
- The Off-the-Record Messaging Library is licensed under version 2.1
of the GNU Lesser General
Public License. The Off-the-Record Toolkit, the pidgin-otr plugin,
and the OTR proxy are licensed under version 2 of the GNU General Public
- How is this different from the pidgin-encryption plugin?
- The pidgin-encryption plugin provides encryption and authentication,
but not deniability or perfect forward secrecy. If an attacker or a
virus gets access to your machine, all of your past
pidgin-encryption conversations are retroactively compromised. Further,
since all of the messages are digitally signed, there is
difficult-to-deny proof that you said what you did: not what we want
for a supposedly private conversation!
- How is this different from Trillian's SecureIM?
- SecureIM doesn't provide any kind of authentication at all! You
really have no idea (in any kind of secure way) to whom you're speaking,
or if there is a "man in the middle" reading all of your messages.
- How is this different from SILC?
- SILC uses a completely separate network of servers and underlying
network protocol. In some environments, such as firewalled or corporate
setups, where a local proprietary IM protocol may be in use, SILC may
not be available. Further, in its normal mode of operation, all SILC messages
are shared with the SILC servers; if you want to send messages that can only
be read by the person with whom you're communicating, you need to either
(1) arrange a pre-shared secret in advance (which hampers perfect forward
secrecy), or (2) be able to do a direct peer-to-peer connection to the other
person's client, in order to do a key agreement (which may not be possible in
a NAT or firewall situation).
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