Off-the-Record Messaging

News - Downloads - Mailing Lists - Documentation - Frequently Asked Questions - Press

Off-the-Record (OTR) Messaging allows you to have private conversations over instant messaging by providing:

Encryption
No one else can read your instant messages.
Authentication
You are assured the correspondent is who you think it is.
Deniability
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.

News

5 Nov 2005
otrproxy-0.3.1 released. Changes from 0.3.0:
5 Nov 2005
gaim-otr-3.0.0 and libotr-3.0.0 released. Changes from 2.0.2:
5 Nov 2005
The identity-binding flaw pointed out earlier has been fixed in version 2 of the OTR Protocol.

More News...

Downloads

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 3.0.0.

README

Source code (3.0.0)
Compressed tarball (sig)
[Note that if you're compiling from source on win32, you may need to make this patch to libgcrypt-1.2.1.]
Linux/x86 (2.0.2)
Fedora Core 4 RPM
Fedora Core 4 dev RPM
Fedora Core 3 RPM
Fedora Core 3 dev RPM
Mandriva 2005 LE RPM
Mandriva 2005 LE dev RPM
Linux/x86 (2.0.1)
Mandrake 10.1 RPM
Mandrake 10.1 dev RPM
Linux/x86_64 (2.0.2)
Fedora Core 4 RPM
Fedora Core 4 dev RPM
Fedora Core 3 RPM
Fedora Core 3 dev RPM
Linux/PPC (2.0.2)
Fedora Core 4 RPM
Fedora Core 4 dev RPM

OTR plugin for gaim

This is a plugin for gaim 1.x which implements Off-the-Record Messaging over any IM network gaim supports. The current version is 3.0.0. You may need the above library packages.

README

Source code (3.0.0)
Compressed tarball (sig)
Patch for gaim 2 beta 2 (will be incorporated into next version)
Linux/x86 (2.0.2)
Fedora Core 4 RPM
Mandriva 2005 LE RPM
Linux/x86 (2.0.1)
Fedora Core 3 RPM
Mandrake 10.1 RPM
Linux/x86_64 (2.0.2)
Fedora Core 4 RPM
Fedora Core 3 RPM
Linux/PPC (2.0.2)
Fedora Core 4 RPM
Windows (3.0.0)
Win32 installer for gaim 1.x (sig)
Win32 installer for gaim 2.x (See this message if you're using gaim 2 beta 2.)

OTR localhost AIM proxy

Notice to Tiger iChat users: You need to be using OS X version 10.4.2 or later. Earlier versions have a bug that prevents iChat from connecting to an HTTP proxy.

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:

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.

README

Source code (0.3.1)
Compressed tarball (sig)
Windows (0.3.1)
Win32 installer (sig)
OS X (0.3.1)
OS X package

Mailing Lists

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.

Documentation

Installation and Setup Guides

Trillian with OTR proxy (German translation, from HennR)
Adium X with OTR
OTR proxy on Mac OS X
gaim-otr on Debian unstable (from Adam Zimmerman)
gaim-otr on Windows(from Adam Zimmerman)
gaim-otr 3.0.0 on Ubuntu(from Adam Zimmerman). Note that Ubuntu breezy has gaim-otr 2.0.2 in it, and all you should have to do is "apt-get install gaim-otr".

We would greatly appreciate instructions and screenshots for other platforms!

About OTR

Here are some documents and papers describing OTR. The CodeCon presentation is quite useful to get started.

Frequently Asked Questions

What implementations of Off-the-Record Messaging are there?
Right now, there's the plugin for gaim, which is supported on Linux and Windows. Adium X, a popular IM client for Mac OS X, supports OTR. There's also the OTR proxy, which is supported on Linux, Windows, and OS X. 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 gaim-otr plugin, and the OTR proxy are licensed under version 2 of the GNU General Public License.
How is this different from the gaim-encryption plugin?
The gaim-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 gaim-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).

Is your question not here? Ask on the otr-users mailing list!

Nikita Borisov, Ian Goldberg