Open Whisper Systems

Open Whisper Systems was a software development group focused on creating open-source, privacy-preserving communication technologies. Founded in 2013 by Moxie Marlinspike and Stuart Anderson, the organization became renowned for developing the widely adopted Signal Protocol and the Signal messaging application. Its work significantly advanced the field of end-to-end encryption for consumer applications, influencing major technology companies and setting new standards for private communication. In 2018, its projects and team transitioned to the newly formed non-profit Signal Technology Foundation.

History and development

The origins trace back to the earlier projects of co-founder Moxie Marlinspike, including the encrypted texting app TextSecure and the encrypted calling app RedPhone, developed by his startup Whisper Systems. Following the acquisition of Whisper Systems by Twitter in 2011, the core software was released as open-source software. In 2013, Marlinspike and Stuart Anderson founded the new entity, merging TextSecure and RedPhone into a single application initially named TextSecure and later rebranded as Signal. The organization operated as a collaborative project, receiving early funding from the Freedom of the Press Foundation and later from a $50 million loan from Brian Acton, co-founder of WhatsApp. This period of development was marked by close collaboration with the Internet Engineering Task Force to standardize encryption techniques.

Signal Protocol

The organization's most significant technical contribution is the Signal Protocol, an end-to-end encryption protocol that secures text, voice, and video communications. The protocol combines the Double Ratchet Algorithm, prekeys, and a X3DH key agreement protocol to provide forward secrecy and future secrecy (post-compromise security). It was first fully implemented in the Signal app. The Signal Protocol has been adopted and integrated by several major technology platforms, including Facebook Messenger's "Secret Conversations," WhatsApp, and Google's Allo (in incognito mode), and Skype. Its design has been extensively analyzed in the academic security community, with papers presented at major conferences like IEEE Symposium on Security and Privacy.

Software applications

The primary consumer-facing product was the Signal application for Android and iOS. The app provided free, open-source messaging and voice/video calls, with all communications secured by the Signal Protocol. The iOS version was initially launched in collaboration with Christine Corbett Moran. Prior to the unified Signal app, the organization maintained separate applications: TextSecure for texting and RedPhone for calls on Android. The development process was conducted transparently on the code repository GitHub, allowing for public scrutiny and contributions. The apps were distributed through the Google Play Store and the Apple App Store.

Security and encryption features

The software implemented state-of-the-art cryptography, mandating end-to-end encryption for all communications by default. Core features included the Double Ratchet Algorithm for perfect forward secrecy within ongoing conversations, Sesame for secure group messaging, and the use of trusted first contact through safety number verification. The protocol was designed to avoid reliance on a global public key infrastructure, instead using a centralized but privacy-respecting key server. The applications also featured sealed sender technology to obscure metadata about the sender, and later integrated support for Samsung's Knox security platform. The codebase underwent independent security audits by firms like Trail of Bits.

Reception and impact

The work received widespread acclaim from the cryptography and digital rights communities. It was endorsed by prominent figures such as Edward Snowden, Bruce Schneier, and the American Civil Liberties Union. The adoption of the Signal Protocol by Facebook for WhatsApp, affecting billions of users, is considered one of the largest deployments of end-to-end encryption in history. The organization's commitment to open-source software and its resistance to incorporating backdoors, even under pressure from agencies like the Federal Bureau of Investigation, set a benchmark for privacy-focused technology companies. Its model directly inspired other secure messaging apps like Wire and influenced the development of the Matrix protocol.

Category:American technology companies Category:Cryptography organizations Category:Open-source software organizations Category:Software companies based in California Category:Defunct technology companies of the United States