Double Ratchet Algorithm: Difference between revisions

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In [[cryptography]], the '''Double Ratchet Algorithm''' (previously referred to as the '''Axolotl Ratchet'''<ref name="Perrin-2016-03-30">{{cite web|last1=Perrin|first1=Trevor|title=Compare Revisions|url=https://github.com/trevp/double_ratchet/wiki/Home/_compare/6fa4a516b01327d736df1f52014d8b561a18189a...ab41721f9ed7ca0bdac3e24ce9fc573750e0614d|website=GitHub|access-date=9 April 2016|date=30 March 2016}}</ref><ref name="signal-inside-and-out">{{cite web|last1=Marlinspike|first1=Moxie|title=Signal on the outside, Signal on the inside|url=https://whispersystems.org/blog/signal-inside-and-out/|publisher=Open Whisper Systems|access-date=31 March 2016|date=30 March 2016}}</ref>) is a [[Key (cryptography)|key]] management algorithm that was developed by [[Trevor Perrin]] and [[Moxie Marlinspike]] in 2013. It can be used as part of a [[cryptographic protocol]] to provide [[end-to-end encryption]] for [[instant messaging]]. After an initial [[key-agreement protocol|key exchange]] it manages the ongoing renewal and maintenance of short-lived session keys. It combines a cryptographic so-called "ratchet" based on the [[Diffie–Hellman key exchange]] (DH) and a ratchet based on a [[key derivation function]] (KDF), such as a [[hash function]], and is therefore called a double ratchet.

The algorithm provides forward secrecy for messages, and implicit renegotiation of forward keys; properties for which the protocol is named.<ref>{{cite journalbook|last1=Cohn-Gordon|first1=K.|last2=Cremers|first2=C.|last3=Garratt|first3=L.|title=On Post-compromise Security|journal=2016 IEEE 29th Computer Security Foundations Symposium (CSF) |chapter=On Post-compromise Security |year=2016|pages=164–178|doi=10.1109/CSF.2016.19|isbn=978-1-5090-2607-4|s2cid=5703986|chapter-url=https://ora.ox.ac.uk/objects/uuid:241da365-1c73-4b6a-826c-f122c4c1e1b8}}</ref>

== History ==

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* [[Conversations (software)|Conversations]]{{efn|name=OMEMO|Via the [[OMEMO]] protocol}}

* [[Cryptocat]]{{efn|name=OMEMO}}<ref>{{Cite web|url=https://crypto.cat/security.html|title=Security|publisher=Cryptocat|access-date=14 July 2016|archive-url=https://web.archive.org/web/20160407125207/https://crypto.cat/security.html|archive-date=7 April 2016|url-status=dead}}</ref>

* [[Facebook Messenger]]{{efn|Only in "secret conversations"}}{{efn|name=SIGNAL|Via the [[Signal Protocol]]}}<ref>{{cite webmagazine|last1=Greenberg|first1=Andy|url=https://www.wired.com/2016/10/facebook-completely-encrypted-messenger-update-now/|title=You Can All Finally Encrypt Facebook Messenger, So Do It|websitemagazine=Wired|publisher=Condé Nast|access-date=5 October 2016|date=4 October 2016}}</ref>

* [[G Data CyberDefense|G Data]] Secure Chat{{efn|name=SIGNAL}}<ref name="G Data"/><ref>{{cite web|title=SecureChat|url=https://github.com/GDATASoftwareAG/SecureChat|website=GitHub|publisher=G Data|access-date=14 July 2016}}</ref>

* [[Gajim]]{{efn|name=OMEMO}}{{efn|name=Plugin|A third-party [[Plug-in (computing)|plug-in]] must be installed separately}}

* [[GNOME Fractal]]{{efn|name=Matrix}}

* [[Google Allo]]{{efn|Only in "incognito mode"}}{{efn|name=SIGNAL}}<ref name="Greenberg-2016-05-18">{{Cite webmagazine|last=Greenberg|first=Andy|url=https://www.wired.com/2016/05/allo-duo-google-finally-encrypts-conversations-end-end/|title=With Allo and Duo, Google Finally Encrypts Conversations End-to-End|websitemagazine=Wired|publisher=Condé Nast|date=18 May 2016|access-date=14 July 2016}}</ref>

* [[Messages (Google)|Google Messages]]{{efn|Only in one-to-one [[Rich Communication Services|RCS chats]]}}{{efn|name=SIGNAL|Via the [[Signal Protocol]]}}<ref>{{Cite web |last=Amadeo |first=Ron |date=2021-06-16 |title=Google enables end-to-end encryption for Android's default SMS/RCS app |url=https://arstechnica.com/gadgets/2021/06/google-enables-end-to-end-encryption-for-androids-default-sms-rcs-app/ |access-date=2022-03-03 |website=Ars Technica |language=en-us}}</ref>

* [[Haven (software)|Haven]]{{efn|name=SIGNAL}}<ref>{{cite web|title=Haven Attributions|url=https://github.com/guardianproject/haven#attributions|website=GitHub|publisher=Guardian Project|access-date=22 December 2017}}</ref><ref>{{cite web|last1=Lee|first1=Micah|title=Snowden's New App Uses Your Smartphone To Physically Guard Your Laptop|url=https://theintercept.com/2017/12/22/snowdens-new-app-uses-your-smartphone-to-physically-guard-your-laptop/|website=The Intercept|publisher=First Look Media|access-date=22 December 2017|date=22 December 2017}}</ref>

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* [[Skype]]{{efn|Only in "private conversations"}}{{efn|name=SIGNAL}}<ref>{{cite web|last1=Lund|first1=Joshua|title=Signal partners with Microsoft to bring end-to-end encryption to Skype|url=https://signal.org/blog/skype-partnership/|publisher=Open Whisper Systems|access-date=11 January 2018|date=11 January 2018}}</ref>

* [[Viber]]{{efn|Viber "uses the same concepts of the "double ratchet" protocol used in Open Whisper Systems Signal application"}}<ref>{{cite web|title=Viber Encryption Overview|url=https://www.viber.com/app/uploads/viber-encryption-overview.pdf|publisher=Viber|date=25 July 2018|access-date=26 October 2018}}</ref>

* [[WhatsApp]]{{efn|name=SIGNAL}}<ref name="Metz-2016-04-05">{{cite webmagazine|last1=Metz|first1=Cade|title=Forget Apple vs. the FBI: WhatsApp Just Switched on Encryption for a Billion People|url=https://www.wired.com/2016/04/forget-apple-vs-fbi-whatsapp-just-switched-encryption-billion-people/|websitemagazine=Wired|publisher=Condé Nast|access-date=5 April 2016|date=5 April 2016}}</ref>

* [[Wire (software)|Wire]]{{efn|name=Proteus|Via the Proteus protocol}}<ref name="Wire Security Whitepaper">{{Cite web|url=https://wire-docs.wire.com/download/Wire+Security+Whitepaper.pdf|title=Wire Security Whitepaper|publisher=Wire Swiss GmbH|date=17 August 2018|access-date=28 August 2020}}</ref>

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