History[edit]

Security researcher Moxie Marlinspike and roboticist Stuart Anderson co-founded Whisper Systems in 2010.^[9][1] The company produced proprietary enterprise mobile security software. Among these were an encrypted texting program called TextSecure and an encrypted voice calling app called RedPhone.^[10] They also developed a firewall and tools for encrypting other forms of data.^[1][11]


On November 28, 2011, Whisper Systems announced that it had been acquired by Twitter. The financial terms of the deal were not disclosed by either company.^[2] The acquisition was done "primarily so that Mr. Marlinspike could help the then-startup improve its security".^[12] Shortly after the acquisition, Whisper Systems' RedPhone service was made unavailable.^[13] Some criticized the removal, arguing that the software was "specifically targeted [to help] people under repressive regimes" and that it left people like the Egyptians in "a dangerous position" during the events of the 2011 Egyptian revolution.^[14]


Twitter released TextSecure as free and open-source software under the GPLv3 license in December 2011.^{[15][16][1][5]} RedPhone was also released under the same license in July 2012.^[17]


Marlinspike later left Twitter and founded Open Whisper Systems as a collaborative Open Source project for the continued development of TextSecure and RedPhone.^[18][6] Open Whisper Systems consisted of a large community of volunteer Open Source contributors, as well as a small team of dedicated grant-funded developers. In November 2015, Open Whisper Systems merged TextSecure with RedPhone and renamed it as Signal.^[19] In 2018, Signal Messenger was incorporated as an LLC by Moxie Marlinspike and Brian Acton and then rolled under the independent non-profit Signal Technology Foundation. Today, the Signal app is developed by Signal Messenger LLC, which is funded by the Signal Foundation.^[7][8] The foundation has stated publicly that they are not tied to any major technology companies and "can never be acquired by one either."^[20]