Silent Circle Instant Messaging Protocol

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The Silent Circle Instant Message Protocol (SCIMP) was an encryption scheme that was developed by Silent Circle. It enabled private conversation over instant message transports such as XMPP (Jabber).[1]

SCIMP provided encryption, perfect forward secrecy and message authentication.[2] It also handled negotiating the shared secret keys.


Silent Circle used SCIMP in their encrypted instant messaging application called Silent Text. Silent Text was discontinued on September 28, 2015, when its features were merged into Silent Circle's encrypted voice calling application called Silent Phone.[3] At the same time, Silent Circle transitioned to using a protocol that uses the Double Ratchet Algorithm instead of SCIMP.[3][4]


  1. ^ "Silent Circle's SCIMP page". Archived from the original on 4 September 2015. Retrieved 13 December 2015. 
  2. ^ Moscaritolo, Vinnie; Belvin, Gary; Zimmermann, Phil (5 December 2012). "Silent Circle Instant Messaging Protocol Protocol Specification" (PDF). Silent Circle. Archived from the original (PDF) on 2 April 2015. Retrieved 31 October 2013. 
  3. ^ a b "What is Silent Phone?". Silent Circle. 17 September 2015. Archived from the original on 4 March 2016. Retrieved 8 March 2016. 
  4. ^ Armasu, Lucian (3 November 2015). "TextSecure, RedPhone Private Communications Apps Now Combined Into 'Signal' App". Tom's Hardware. Purch Group, Inc. Retrieved 8 March 2016.