Silent Circle (software)

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Silent Circle
FoundedOctober 2011 (2011-10)
Washington DC, United States
Key people
Gregg Smith - CEO

Silent Circle is an encrypted communications firm based in Washington DC.[1] Silent Circle provides multi-platform secure communication services for mobile devices and desktop. Launched October 16, 2012, the company operates under a subscription business model.[2] The encryption part of the software used is free software/open source and peer-reviewed.[2] For the remaining parts of Silent Phone and Silent Text, the source code is available on GitHub, but under proprietary software licenses.[3]


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.[4][5] The company was founded in the Caribbean island of Nevis, but moved its headquarters to Le Grand-Saconnex[6] near Geneva, Switzerland in 2014 in search of a country with "stronger privacy laws to protect its customers' information."[7]

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 March 2015 there was a controversy when Information Security specialist and hacker Khalil Sehnaoui identified that Silent Circle's warrant canary had been removed from their site.[11]

In January 2017 Gregg Smith was named CEO with a renewed focus on serving the large business space as well as Government entities. At the same time Tony Cole, VP and Global Government CTO of FireEye, was named to the Board of Directors.[12] Shortly after Smith became CEO, the company moved back from Switzerland to the United States.[13]


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.[14]

However, as of August 2020, the page for the secure messaging scorecard states that it is out of date and should not be used in privacy- and security-related decision-making.


The company's products[15] 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.[16]


Its discontinued products include the following:

  • Blackphone: A smartphone designed for privacy created by Silent Circle and built by SGP Technologies, a joint venture between Silent Circle and Geeksphone. There have been no more news nor updates since 2018. PrivatOS was Discontinued June 30, 2016.[17]
  • GoSilent: Personal Firewall with integrated VPN and Cloud Analytics. The product was introduced after Silent Circle acquired Maryland start-up Kesala. It was sold by Silent Circle's new owner in 2018[18]
  • Silent Text: Discontinued September 28, 2015.[16] 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.[16]
  • 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[5] and operates under a subscription business model.[2]

See also[edit]


  1. ^ O'Neill, Patrick Howell (27 July 2017). "Back in America with a black eye, Silent Circle rebuilds with focus on software". Retrieved 22 May 2020.
  2. ^ 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.
  3. ^ "SilentCircle". GitHub. Retrieved 2015-05-23.
  4. ^ Bort, Julie. "An Internet Hall Of Famer And Some Navy SEALs Want To Make Your iPhone Safer". Business Insider, Inc. Retrieved 12 March 2013.
  5. ^ a b Takahashi, Dean (8 August 2014). "Crypto wiz Phil Zimmermann leads charge to make phone calls really private". Venturebeat. Retrieved 26 January 2015.
  6. ^ Moneyhouse: Silent Circle SA (excerpt from the commercial register)
  7. ^ Ranger, Steve (23 June 2015). "Defending the last missing pixels: Phil Zimmermann speaks out on encryption, privacy, and avoiding a surveillance state". TechRepublic.
  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. ^ "Silent Circle: We haven't been served a single demand for data". ZDNet. CBS Interactive. 8 March 2015. Retrieved 3 November 2015.
  12. ^ "Silent Circle Appoints Gregg Smith as Chief Executive Officer".
  13. ^
  14. ^ "Secure Messaging Scorecard. Which apps and tools actually keep your messages safe?". Electronic Frontier Foundation. 2014-11-04.
  15. ^ Ridden, Paul. "PGP creator aims to keep digital communications strictly confidential with Silent Circle". Gizmag. Retrieved 12 March 2013.
  16. ^ a b c "What is Silent Phone?". Silent Circle. 17 September 2015. Retrieved 4 October 2015.
  17. ^ "A Eulogy: PrivatOS. June 1, 2014 – June 30, 2016 - Privacy Delivered" (Blog). Silent Circle. 30 June 2016. Archived from the original on 18 August 2016. Retrieved 9 February 2020.
  18. ^ "Attila Security raises $2.5M, moves into Fulton-based DataTribe".

Further reading[edit]

External links[edit]