Silent Circle (software)

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Silent Circle
Industry Software
Founded October 2011 (2011-10)
Headquarters Le Grand-Saconnex, Canton of Geneva, Switzerland (legal domicile)[1]
Key people
  • Matt Neiderman (interim CEO)[2]

Silent Circle is an encrypted communications firm based in the Canton of Geneva, Switzerland.[3] Silent Circle provides multiplatform secure communication services for mobile devices and desktop. Launched October 16, 2012, the company operates under a subscription business model.[4] The encryption part of the software used is free software/open source and peer-reviewed.[4] For the remaining parts of Silent Phone and Silent Text, the source code is available on GitHub, but under proprietary software licences.[5]


In November 2011, Mike Janke called Phil Zimmermann with an idea for a new kind of private, secure version of Skype. Zimmermann agreed to the project and called Jon Callas, co-founder of PGP Corporation and Vincent Moscaritolo. Janke brought in security expert Vic Hyder, and the founding team was established.[6][7] The company was founded in Nevis, but moved its headquarters to Geneva, Switzerland in 2014 in search of a country with "stronger privacy laws to protect its customers' information."[3]

On August 9, 2013, through their website, Silent Circle announced that the Silent Mail service would be shut down, because the company could "see the writing on the wall" and felt it was not possible to sufficiently secure email data with the looming threat of government compulsion and precedent set by the Lavabit shutdown the day before.[8]

In January 2015, Silent Text had a serious vulnerability that allowed an attacker to remotely take control of a Blackphone device.[9] A potential attacker only needed to know the target’s Silent Circle ID number or phone number.[9] Blackphone and Silent Circle patched the vulnerability shortly after it had been disclosed.[10]


In November 2014, Silent Phone and Silent Text received top scores on the Electronic Frontier Foundation's secure messaging scorecard, along with "ChatSecure + Orbot", Cryptocat, TextSecure, and "Signal / RedPhone". They received points for having communications encrypted in transit, having communications encrypted with keys the providers don't have access to (end-to-end encryption), making it possible for users to independently verify their correspondent's identities, having past communications secure if the keys are stolen (forward secrecy), having their code open to independent review (open source), having their security designs well-documented, and having recent independent security audits.[11]


The company's products[12] enable encrypted mobile phone calls, text messaging, and video chat.


Its current products include the following:

  • Silent Phone: Encrypted voice calls, video calls and text messages on mobile devices. Currently available for iOS, Android, and Silent Circle’s Silent OS on Blackphone. It can be used with Wi-Fi, EDGE, 3G or 4G cellular anywhere in the world.[13]
  • Blackphone A smartphone designed for privacy created by Silent Circle and built by SGP Technologies, a joint venture between Silent Circle and Geeksphone.


Its discontinued products include the following:

  • Silent Text: Discontinued September 28, 2015.[13] A stand-alone application for encrypted text messaging and secure cloud content transfer with “burn notice” feature for permanently deleting messages from devices. Its features were merged into Silent Phone.[13]
  • Silent Mail: Discontinued August 9, 2013. Silent Mail used to offer encrypted email on Silent Circle’s private, secure network and compatibility with popular email client software.[8]

Business model[edit]

The company is privately funded[7] and operates under a subscription business model.[4]

See also[edit]


  1. ^ "Commercial register: Silent Circle SA". Retrieved 3 November 2015. 
  2. ^ Fox-Brewster, Thomas (6 July 2016). "Sorry Privacy Lovers, The Blackphone Is Flirting With Failure". Forbes. Forbes, Inc. Retrieved 8 July 2016. 
  3. ^ a b Ranger, Steve (23 June 2015). "Defending the last missing pixels: Phil Zimmermann speaks out on encryption, privacy, and avoiding a surveillance state". TechRepublic. 
  4. ^ a b c Ungerleider, Neal (5 October 2012). "Phil Zimmermann's Silent Circle Builds A Secure, Seductive Fortress Around Your Smartphone". Fast Company. Retrieved 2015-05-23. 
  5. ^ "SilentCircle". GitHub. Retrieved 2015-05-23. 
  6. ^ Bort, Julie. "An Internet Hall Of Famer And Some Navy SEALs Want To Make Your iPhone Safer". Business Insider, Inc. Retrieved 12 March 2013. 
  7. ^ a b Takahashi, Dean (8 August 2014). "Crypto wiz Phil Zimmermann leads charge to make phone calls really private". Venturebeat. Retrieved 26 January 2015. 
  8. ^ a b Tsukayama, Hayley (Aug 9, 2013). "Lavabit, Silent Circle shut down e-mail: What alternatives are left?". Washington Post. Retrieved 10 August 2013. 
  9. ^ a b Dowd, Mark (27 January 2015). "BlackPwn: BlackPhone SilentText Type Confusion Vulnerability". Azimuth Security. Retrieved 1 December 2015. 
  10. ^ Mimoso, Michael (28 January 2015). "Memory Corruption Bug Patched in Blackphone Silent Text App". Threatpost. Kaspersky Lab. Retrieved 1 December 2015. 
  11. ^ "Secure Messaging Scorecard. Which apps and tools actually keep your messages safe?". Electronic Frontier Foundation. 2014-11-04. 
  12. ^ Ridden, Paul. "PGP creator aims to keep digital communications strictly confidential with Silent Circle". Gizmag. Retrieved 12 March 2013. 
  13. ^ a b c "What is Silent Phone?". Silent Circle. 17 September 2015. Retrieved 4 October 2015. 

Further reading[edit]

External links[edit]