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Moxie Marlinspike
Moxie Marlinspike is an American entrepreneur, cryptographer, and computer security researcher. Marlinspike is the creator of Signal, co-founder of the Signal Technology Foundation, and served as the first CEO of Signal Messenger LLC. He is also a co-author of the Signal Protocol encryption used by Signal, WhatsApp, Google Messages, Facebook Messenger, and Skype.
Marlinspike is a former head of the security team at Twitter and the author of a proposed SSL authentication system replacement called Convergence. He previously maintained a cloud-based WPA cracking service and a targeted anonymity service called GoogleSharing.
Marlinspike began his career working for several technology companies, including enterprise infrastructure software maker BEA Systems Inc.
In 2010, Marlinspike was the chief technology officer and co-founder of Whisper Systems, an enterprise mobile security startup company. In May 2010, Whisper Systems launched TextSecure and RedPhone. These were applications that provided end-to-end encrypted SMS messaging and voice calling, respectively. Twitter acquired the company for an undisclosed amount in late 2011. The acquisition was done "primarily so that Mr. Marlinspike could help the then-startup improve its security". During his time as Twitter's head of cybersecurity, the firm made Whisper Systems' apps open source.
Marlinspike left Twitter in early 2013 and founded Open Whisper Systems as a collaborative open source project for the continued development of TextSecure and RedPhone. At the time, Marlinspike and Trevor Perrin started developing the Signal Protocol, an early version of which was first introduced in the TextSecure app in February 2014. In November 2015, Open Whisper Systems unified the TextSecure and RedPhone applications as Signal. Between 2014 and 2016, Marlinspike worked with WhatsApp, Facebook, and Google to integrate the Signal Protocol into their messaging services.
In 2017, Marlinspike assisted the cryptocurrency company MobileCoin as an early technical advisors alongside fellow former DARPA researcher Todd Huffman. MobileCoin was designed to be the in-app payments for Signal and Mixin Messenger.
On February 21, 2018, Marlinspike and WhatsApp co-founder Brian Acton announced the formation of the Signal Technology Foundation and its subsidiary, Signal Messenger LLC. Marlinspike served as Signal Messenger's first CEO until stepping down on January 10, 2022. In the wake of the United States government group chat leak Marlinspike posted in March 2025 "There are so many great reasons to be on Signal. Now including the opportunity for the vice president of the United States of America to randomly add you to a group chat for coordinating sensitive military operations. Don't sleep on this opportunity..."
In a 2009 paper, Marlinspike introduced the concept of SSL stripping, a man-in-the-middle attack in which a network attacker could prevent a web browser from upgrading to an SSL connection in a way that would likely go unnoticed by a user. He also announced the release of a tool, sslstrip, that would automatically perform these types of man-in-the-middle attacks. The HTTP Strict Transport Security (HSTS) specification was subsequently developed to combat these attacks.
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Moxie Marlinspike
Moxie Marlinspike is an American entrepreneur, cryptographer, and computer security researcher. Marlinspike is the creator of Signal, co-founder of the Signal Technology Foundation, and served as the first CEO of Signal Messenger LLC. He is also a co-author of the Signal Protocol encryption used by Signal, WhatsApp, Google Messages, Facebook Messenger, and Skype.
Marlinspike is a former head of the security team at Twitter and the author of a proposed SSL authentication system replacement called Convergence. He previously maintained a cloud-based WPA cracking service and a targeted anonymity service called GoogleSharing.
Marlinspike began his career working for several technology companies, including enterprise infrastructure software maker BEA Systems Inc.
In 2010, Marlinspike was the chief technology officer and co-founder of Whisper Systems, an enterprise mobile security startup company. In May 2010, Whisper Systems launched TextSecure and RedPhone. These were applications that provided end-to-end encrypted SMS messaging and voice calling, respectively. Twitter acquired the company for an undisclosed amount in late 2011. The acquisition was done "primarily so that Mr. Marlinspike could help the then-startup improve its security". During his time as Twitter's head of cybersecurity, the firm made Whisper Systems' apps open source.
Marlinspike left Twitter in early 2013 and founded Open Whisper Systems as a collaborative open source project for the continued development of TextSecure and RedPhone. At the time, Marlinspike and Trevor Perrin started developing the Signal Protocol, an early version of which was first introduced in the TextSecure app in February 2014. In November 2015, Open Whisper Systems unified the TextSecure and RedPhone applications as Signal. Between 2014 and 2016, Marlinspike worked with WhatsApp, Facebook, and Google to integrate the Signal Protocol into their messaging services.
In 2017, Marlinspike assisted the cryptocurrency company MobileCoin as an early technical advisors alongside fellow former DARPA researcher Todd Huffman. MobileCoin was designed to be the in-app payments for Signal and Mixin Messenger.
On February 21, 2018, Marlinspike and WhatsApp co-founder Brian Acton announced the formation of the Signal Technology Foundation and its subsidiary, Signal Messenger LLC. Marlinspike served as Signal Messenger's first CEO until stepping down on January 10, 2022. In the wake of the United States government group chat leak Marlinspike posted in March 2025 "There are so many great reasons to be on Signal. Now including the opportunity for the vice president of the United States of America to randomly add you to a group chat for coordinating sensitive military operations. Don't sleep on this opportunity..."
In a 2009 paper, Marlinspike introduced the concept of SSL stripping, a man-in-the-middle attack in which a network attacker could prevent a web browser from upgrading to an SSL connection in a way that would likely go unnoticed by a user. He also announced the release of a tool, sslstrip, that would automatically perform these types of man-in-the-middle attacks. The HTTP Strict Transport Security (HSTS) specification was subsequently developed to combat these attacks.