||This article contains content that is written like an advertisement. (October 2014)|
Screenshot of Cryptocat 2.1.5
|Original author(s)||Nadim Kobeissi|
|Developer(s)||Cryptocat contributors |
|Initial release||19 May 2011|
|Stable release||2.2.2 / June 12, 2014|
|Available in||English, Arabic, Bulgarian, Burmese, Catalan, Chinese, Czech, Danish, Dutch, Farsi, French, German, Greek, Hebrew, Hungarian, Italian, Japanese, Korean, Latvian, Norwegian, Polish, Portuguese, Romanian, Russian, Slovenian, Spanish, Swedish, Tibetan|
|License||Affero General Public License|
Cryptocat is an open source web and mobile application intended to allow secure, encrypted online chatting. Cryptocat uses end-to-end encryption and encrypts chats on the client side, only trusting the server with data that is already encrypted. Cryptocat is offered as an app for Mac OS X or as a browser extension for Google Chrome, Mozilla Firefox, Apple Safari, Opera and as a mobile app for iPhone.
Cryptocat's stated goal is to make encrypted communications more accessible to average users. The chat software aims to strike a balance between security and usability—offering more privacy than services such as Google Talk or Internet Relay Chat, while maintaining a higher level of accessibility than Pidgin.
Cryptocat is developed by the Cryptocat team and is released under the GPLv3 license.
Cryptocat was first launched on 19 May 2011.
In June 2012, Cryptocat developer Nadim Kobeissi said he was detained at the U.S. border by the DHS and questioned about Cryptocat's censorship resistance. He tweeted about the incident afterwards, resulting in media coverage and a spike in the popularity of the software.
Along with Threema and Surespot, Cryptocat was ranked first in a study evaluating the security and usability of instant messaging encryption software, conducted by the German PSW Group in June 2014.
In November 2014, Cryptocat received a top score on the Electronic Frontier Foundation's secure messaging scorecard, along with "ChatSecure + Orbot", TextSecure, "Signal / RedPhone", Silent Phone, and Silent Text. They received points for having communications encrypted in transit, having communications encrypted with keys the providers don't have access to (end-to-end encryption), making it possible for users to independently verify their correspondent's identities, having past communications secure if the keys are stolen (forward secrecy), having their code open to independent review (open source), having their security designs well-documented, and having recent independent security audits.
Cryptocat allows any desktop with a modern web browser to quickly set up an end-to-end encrypted chat environment. The browser's accessibility is frequently touted by the project as the reason why it chose the platform. Cryptocat is currently compatible with Google Chrome, Mozilla Firefox, Apple Safari, Opera and also offers an application for iOS devices.
Cryptocat uses the Off-the-Record Messaging (OTR) protocol for encrypted private messaging, allowing two parties to chat in private. Cryptocat also uses its own group messaging protocol to allow for group instant messaging conversations. Since Cryptocat generates new key pairs for every chat, it implements a form of perfect forward secrecy. Cryptocat also offers encrypted file and photo sharing, allowing users to send documents and photos to each other using end-to-end encryption.
Cryptocat also may be used in conjunction with Tor in order to anonymize the client's network traffic. The project also plans to create an embedded version for use with Raspberry Pi devices for use by non-profits. As of July 2013, a Commotion-compatible version was in development.
Since 2013, Cryptocat has offered the ability to connect to Facebook Messenger to initiate encrypted chatting with other Cryptocat users. According to the developers, the feature was meant to help offer an alternative to the regular Cryptocat chat model which does not offer long-term contact lists.
Cryptocat uses the Off-the-Record Messaging (OTR) protocol for encrypted private messaging, allowing two parties to chat in private. For group messaging, Cryptocat uses a group chat protocol deploying Curve25519, AES-256, and HMAC-SHA512, all industry standards for cryptography applications. All messages sent in Cryptocat, including group chat messages and file transfers, are end-to-end encrypted, which means that they can only be read by the intended recipients and not by the network during transit. Cryptocat provides cryptographic properties of confidentiality, integrity, authentication and forward secrecy for all conversations, and also provides deniability for file transfers and private OTR chats.
Cryptocat also publishes its server configuration files and instructions for others to set up their own servers for the Cryptocat client to connect to.
In June 2013, security researcher Steve Thomas pointed out a security bug that could be used to decrypt any group chat message that had taken place using Cryptocat between September 2012 and April 19, 2013. Private messages were not affected, and the bug had been resolved a month prior. In response, Cryptocat issued a security advisory, requested that all users ensure that they had upgraded, and informed users that past group conversations may have been compromised.
In February 2014, an audit by iSec Partners criticized Cryptocat's authentication model as insufficient. In response, Cryptocat made improvements to user authentication, making it easier for users to authenticate and detect man-in-the-middle attacks.
Some versions of Cryptocat have been questioned for utilizing the browser to encrypt messages, which some researchers feel is less secure than the desktop environment. More recent versions have relied on browser-native random number generation.
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