Cryptocat

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Cryptocat

logo
Chat window
Cryptocat 2.1.5
Basic data

developer Nadim Kobeissi u. a.
Publishing year May 19, 2011
Current  version 3.2.08
(February 20, 2017)
operating system Linux , Windows , macOS
programming language JavaScript
category bug-proof communication
License AGPL / GPL ( free software )
German speaking Yes
crypto.cat

Cryptocat was free software for end-to-end encrypted chat . Messages could not be decrypted on the entire transmission path. Work on the project was stopped by Nadim Kobeissi and the necessary servers were switched off.

history

Cryptocat was first released in 2011. Cryptocat was initially offered as a web application on a website, which means that the program code had to be delivered again for each application and is only authenticated by the system of TLS certification authorities , which is prone to middleman attacks due to its unmanageably large attack surface . Nadim initially defended this method for over a year, claiming it was safe as long as the delivering server was not compromised. Instead, Cryptocat is now offered as browser extensions signed by the browser manufacturers, which are available locally.

Cryptocat developer Nadim Kobeissi said he was detained at the US border by the United States Department of Homeland Security in June 2012 and questioned about Cryptocat's resistance to censorship. He later tweeted about the incident, which sparked media coverage and a surge in popularity of the software.

In November 2012 it became known that Cryptocat used initialization nonces for the counter mode of the AES block encryption several times, since both conversation partners started with the same value. Cryptocat now starts with random nonces and transmits and saves nonces used in order to discard messages and issue warning messages if they are reused.

In the same month, results of an independent code review by Mario Heiderich et al. published which pointed out a weakness in cross-site scripting .

In June 2013, Cryptocat was used by the journalist Glenn Greenwald during his stay in Hong Kong to meet the NSA whistleblower Edward Snowden for the first time after other encryption software had failed. In November 2013, Cryptocat was banned in Iran shortly after Iran's new President Hassan Rohani was elected, who had promised more open Internet legislation.

Since 2013, Cryptocat has been able to connect to Facebook Messenger in order to establish encrypted conversation sessions with other Cryptocat users.

After Apple initially refused to include the iOS app in its app store for secret reasons on December 27, 2013 , it is now also available there.

In 2014, Cryptocat introduced improved user authentication to make it easier to detect middleman attacks. The improvements were made after an audit by iSec Partners criticized the previous process as insufficient.

In a study carried out by the German PSW Group in June 2014 on data security and usability of instant message encryption software, Cryptocat was rated the best next to Threema and Surespot . In November 2014, Cryptocat scored 7 out of 7 on the Electronic Frontier Foundation's secure text messaging rating list . In the same year the software received the international Elevate Award.

On February 19, 2016, Cryptocat was removed from the Google Web Store, apparently by the author himself. Nadim Kobeissi then reported on Twitter and pointed out a letter to users on the Cryptocat website, which was about the future of Cryptocat. The letter stated that the service would be temporarily completely suspended until a complete reprogramming of the code was completed. Kobeissi justified the temporary suspension of the messenger by saying that it was out of date. He also wrote that the future version will only be available as a desktop client, and no longer as an extension for the browser as before, and that many interesting technologies that he is working on at INRIA will be integrated . From other Twitter posts it could be read that the new Cryptocat will have functions such as emoticons, sending files or a friends list, and it will still be possible to create accounts. crypto.cat: Dear Cryptocat users ( Memento from February 19, 2016 in the Internet Archive )

The new version of CryptoCat was released at the end of May 2016 and, according to the developers, was downloaded over 10,000 times within 24 hours, and one month later the software had already recorded over a million downloads.

On February 5, 2019, the team announced that they would no longer develop CryptoCat and that the service would be discontinued on the following day. As an alternative, we recommend the Messenger Wire . The domain crypto.cat is currently for sale.

purpose

Cryptocat is offered as an extension for most common web browsers or as application software ("app") for GNU / Linux , Windows , macOS , iOS and Android (beta). It is mainly developed by Nadim Kobeissi and published as free software in the source code . The browser extensions are available under the conditions of version 3 of the GNU Affero General Public License (AGPL), the stand-alone applications under version 3 of the GNU General Public License (GPL).

Cryptocat's stated goal is to make securely encrypted communication more accessible to average users. The chat software is intended to reconcile data security and ease of use while offering more confidentiality than services such as Google Talk or Internet Relay Chat , while maintaining a higher level of user-friendliness than with Pidgin . Cryptocat was involved in the development of (standardized) basic technology for cryptographic web applications in general and is therefore also seen as a pioneer for a new generation of particularly user-friendly, browser-based encryption applications.

Several serious errors in the encryption system were discovered by 2013. After several professional security checks, no other serious issues were discovered and Cryptocat made it to a recommendation by the Electronic Frontier Foundation (EFF). Developers still refer to it as unfinished and warn not to trust the software with your life.

features

Cryptocat enables an end-to-end encrypted chat environment to be set up quickly on any desktop computer with a modern web browser. Cryptocat is currently compatible with Google Chrome , Mozilla Firefox , Safari and Opera as well as iOS devices and macOS .

All messages sent via Cryptocat, including group chat messages and file transfers, are end-to-end encrypted , meaning that the entire transmission system is only entrusted with encrypted data en route, for which only the intended recipients have the appropriate decryption keys. Cryptocats cryptography ensures confidentiality, integrity, authentication and lack of consequences in all conversations and offers additional deniability for file transfers and one-to-one conversations with OTR. Cryptocat provides end-to-end encryption with no consequences when keys are lost (English forward secrecy ) and repudiation ( deniability ), both single as well as group discussions and file transfers.

Cryptocat itself does not offer a solution for permanent contact lists . As an alternative, a function for integrating the Facebook Messenger has been implemented.

Cryptocat itself does not offer a solution for anonymizing traffic data. The project is planning a version for non-profit organizations for embedded use in Raspberry Pi devices. In July 2013, the development of a Commotion network compatible version began.

architecture

The client software is implemented as a browser extension or as a native application for Mac OS X and iOS. The widespread use of web browsers is often cited as the reason for choosing this platform.

Encryption

Cryptocat uses the off-the-record messaging protocol (OTR), which enables encrypted message transmission between two parties involved. It also uses its own protocol for encrypting group calls , which is based on Curve25519 , AES -256 and HMAC - SHA512 , all of which represent industry standards for cryptographic applications . Since Cryptocat generates new key pairs for every conversation, it implements a form of non-consequence .

The encryption for file transfers is based on traditional OTR. OTR provides the one-time key, from which the actual encryption key and data for authentication are derived using SHA512. The file is then encrypted in 63 kilobyte sections via AES256 in counter mode . An authentication check value obtained by means of HMAC for the encrypted data is added. Then an XMPP file transfer is initiated (according to XEP-0096) and the encrypted file is transferred with XMPP as a so-called "In Band Byte Stream" (according to XEP-0047).

network

Cryptocats network is based on Extensible Messaging and Presence Protocol (XMPP) and Bidirectional-streams Over Synchronous HTTP (BOSH). The system only transports data and does not save anything according to the data protection guidelines of the project. The project uses ejabberd and nginx for the XMPP-BOSH relay. In addition to the client-side end-to-end encryption, communication between client and server is secured with Transport Layer Security (TLS / SSL).

Cryptocat publishes its server configuration files and instructions for others to set up their own servers for use with the Cryptocat client.

In 2013, Cryptocats Server was migrated to the Swedish internet service provider Bahnhof , which also served WikiLeaks and The Pirate Bay . The servers are located in Stockholm in a Cold War bunker .

Security concerns

Some versions of Cryptocat have been criticized because they use the browser to encrypt messages, which some researchers consider to be less secure than the desktop environment. More recent versions were based on the browser's own random number generation.

After doubts about the security of TLS as a whole, Cryptocat's TLS certificate was pinned to Google Chrome and Chromium.

In July 2013, security researcher Steve Thomas reported a problem with the conversion of values ​​from the actually secure pseudo-random number generator .

Decryptocat

In the same month, Steve Thomas drew attention to another vulnerability that can be used to decrypt any group message that was encrypted with Cryptocat between September 2012 and April 19, 2013. This most serious error to date was caused by not taking into account the weak typing of JavaScript . When generating the key, 32 decimal places were generated instead of 32 bytes, each of which can have 256 values. This reduced the key strength from a complexity of around 2,250 to around 2,54 . One-on-one messages were not affected and the bug had been fixed a month earlier. Two external code checks, by Cure53 and VeraCode, overlooked this error. After Thomas' discoveries were published, Cryptocat issued a security advisory urging all users to ensure that their software was updated. Since 2011 there has been a warning on the homepage of the website and in the software itself about the experimental nature of the project. A warning was posted on the Cryptocat blog explaining to users that group conversations made through the software may have been broken in the past.

Web links

Commons : Cryptocat  - collection of images, videos and audio files

Individual evidence

  1. ↑ Nadim Kobeissi. In: GitHub . Retrieved May 4, 2017 .
  2. ↑ Cryptocat 3.2.08 Release Notes. (No longer available online.) In: crypto.cat. Archived from the original on March 6, 2019 ; accessed on September 9, 2019 (English).
  3. ↑ Adam Dachis: cryptocat Creates to Encrypted, Disposable Chat Room on Any computer with a Web browser . In: Lifehacker , August 9, 2011. Retrieved April 8, 2012. 
  4. ^ Justin Giovannetti: Encrypted messages: chatting safely with Cryptocat . In: OpenFile , February 4, 2012. Archived from the original on February 6, 2012 Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . Retrieved April 8, 2012. @1@ 2Template: Webachiv / IABot / montreal.openfile.ca 
  5. ↑ Nadim Kobeissi: Explanation for the shutdown of the website. Retrieved March 13, 2019 .
  6. ↑ Jesse Burns (iSec Partners), Peter Eckersley (EFF); December 28, 2010: Is the SSLiverse a safe place? An update on EFF's SSL Observatory project.
  7. ↑ Jon Matonis: Detaining Developer At US Border Increases Cryptocat Popularity . Forbes. April 18, 2012. Retrieved July 28, 2012.
  8. ^ Developer's detention spikes interest in Montreal's Cryptocat . Itbusiness.approx. June 8, 2012. Retrieved July 28, 2012.
  9. ^ Glenn Greenwald: No Place to Hide: Edward Snowden, the NSA, and the US Surveillance State . Metropolitan Books, May 13, 2014, ISBN 978-1-62779-073-4 , p. 59, (accessed June 22, 2014).
  10. ↑ Lorenzo Franceschi-Bicchierai: Iran Blocks Encrypted Chat Service Despite Claims of Internet Freedom . In: Mashable , November 21, 2013. Retrieved June 22, 2014. 
  11. ↑ a b Quinn Norton: Cryptocat Creates an Encrypted, Disposable Chatroom on Any Computer with a Web Browser . In: The Daily Beast , May 12, 2014. Retrieved June 22, 2014. 
  12. ↑ Henning Steier: Encrypted Chats: Cryptocat does not make it into the App Store . Neue Zürcher Zeitung, December 30, 2013
  13. ↑ itunes.apple.com
  14. ↑ Recent Audits and Coming Improvements . Cryptocat. Archived from the original on October 15, 2014. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved June 22, 2014.  @1@ 2Template: Webachiv / IABot / blog.crypto.cat
  15. ↑ Christian Heutger: The results of our large messenger test . Retrieved June 26, 2014.
  16. ↑ Secure Messaging Scorecard. Which apps and tools actually keep your messages safe? . Electronic Frontier Foundation. November 4, 2014. Retrieved December 4, 2014.
  17. ↑ Cryptocat Twitter: New Cryptocat downloaded 10,000+ times in first 24 hours. March 31, 2016, accessed May 16, 2019 .
  18. ↑ CryptoCat Twitter: Cryptocat statistics 1 million + downloads. May 6, 2016, accessed on May 16, 2019 .
  19. ^ Cryptocat Twitter: We are discontinuing the Cryptocat service starting tomorrow. February 5, 2019, accessed on May 16, 2019 .
  20. ^ Gabriel-fm / cryptocat-android. In: GitHub. Retrieved September 18, 2016 .
  21. ↑ Andy Greenberg: Crypto.cat Aims To Offer Super-Simple Encrypted Messaging . In: Forbes , May 27, 2011. Retrieved April 8, 2012. 
  22. ↑ Christopher Curtis: Free encryption software Cryptocat protects right to privacy: inventor . In: Montréal Gazette , February 17, 2012. Archived from the original on February 19, 2012. Retrieved on April 8, 2012. 
  23. ↑ Using His Software Skills With Freedom, Not a Big Payout, in Mind . In: New York Times , April 18, 2012.  
  24. ↑ Erich Möchel: Browsers as universal encryption tools . FM4, November 9, 2014
  25. ↑ Hanno Böck: Cryptocat: Encrypted chat system broken . golem.de; 4th July 2013
  26. ↑ Hanno Böck: Encryption: EFF recommends secure messengers . golem.de; 5th November 2014
  27. ^ Cryptocat on the Chrome Web Store . Chrome.google.com. Archived from the original on June 15, 2012. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved July 28, 2012.  @1@ 2Template: Webachiv / IABot / chrome.google.com
  28. ^ Cryptocat, Now with Encrypted Facebook Chat . Cryptocat. Archived from the original on November 11, 2014. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved June 22, 2014.  @1@ 2Template: Webachiv / IABot / blog.crypto.cat
  29. ↑ Jamillah Knowles: Raspberry Pi network plan for online free-speech role . In: BBC News , March 3, 2012. Retrieved April 8, 2012. 
  30. ↑ Jeremy Kirk: Cryptocat Aims for Easy-to-use Encrypted IM Chat . In: PCWorld , March 14, 2012. Archived from the original on December 17, 2012 Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . Retrieved April 8, 2012. @1@ 2Template: Webachiv / IABot / www.pcworld.com 
  31. ↑ Nadim : Documenting and Presenting Vulnerabilities in Cryptocat . (No longer available online.) Cryptocat Blog , November 11, 2013, archived from the original on June 23, 2014 ; accessed on February 5, 2019 (English, original website no longer available).
  32. ^ Cryptocat Multiparty Protocol Specification.Retrieved December 28, 2013
  33. ↑ Cryptocat Privacy Policy . Cryptocat. Retrieved June 22, 2014.
  34. ↑ Server Deployment Instructions . Cryptocat. Retrieved June 22, 2014.
  35. ^ Nadim Kobeissi: Cryptocat Network Now in Swedish Nuclear Bunker . Archived from the original on April 7, 2013. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved February 9, 2013. @1@ 2Template: Webachiv / IABot / blog.crypto.cat
  36. ↑ " JavaScript crypto in the browser is pointless and insecure. "
  37. ↑ Matasano Web Security Assessments for Enterprises Matasano Security
  38. ↑ Thoughts on Critiques of JavaScript Cryptography . ( Memento of the original from September 21, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Nadim Kobeissi  @1@ 2Template: Webachiv / IABot / log.nadim.cc
  39. ↑ HOPE 9: Why Browser Cryptography Is Bad & How We Can Make It Great on Vimeo ( Memento of the original from September 21, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / vimeo.com
  40. ↑ window.crypto.getRandomValues. Mozilla Developer Network
  41. ↑ Google Chromium source code commits . Google. Retrieved September 9, 2013.
  42. ↑ Steve Thomas: DecryptoCat . Retrieved July 10, 2013.
  43. ↑ a b c New Critical Vulnerability in Cryptocat: Details . Cryptocat Development Blog. Archived from the original on July 5, 2013. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved July 7, 2013.  @1@ 2Template: Webachiv / IABot / blog.crypto.cat