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Secure Communications Interoperability Protocol

Secure Communications Interoperability Protocol, abbreviated SCIP, is a standard for secure voice and data communication, developed and endorsed by the Digital Voice Processor Consortium (DDVPC) of the US Department of Defense in cooperation with the National Security Agency (NSA). SCIP is based on the government's earlier Future Narrowband Digital Terminal (FNBDT) project, and is platform-independant as it makes no assumptions about the underlying hardware. The first SCIP devices were used in the US in 2001 (FNBDT).

The major success of SCIP however, came after the US decided to share the SCIP technology with a number of other nations in 2003. Since then, a wide range of SCIP-compatible devices have been developed in various countries. SCIP supports different modes of operation, including national (US) and multi-national modes with different types of encryption.

SCIP can be used over a variety of voice-capable communication systems, such as PSTN telephone lines, ISDN, radio links, satellites, cellular phones and internet (Voice over IP, or VoIP). It was designed to make no assumptions about the underlying hardware. The only requirement is a minimum bandwidth of 2400 Hz. Once a SCIP device connects to another SCIP device, they first negiotiate the parameters and then choose the best possible mode of operation automatically.

By migrating to SCIP, all systems for secure communication used by the US Government will eventually be compatible, which was not the case in the past when different systems were used. In 2006, an upgrade for existing Secure Teminal Equipment (STE) was released, making it SCIP compatible. The older STU-III secure phones can not be made SCIP compatible and have therefore been phased out from 2009 onwards. A good desciption of SCIP can be found on Wikipedia [1].

SCIP devices on this website
Secure Terminal Equipment
vIPer Universal Secure Phone
Known SCIP compatible devices
  1. Project CONDOR was an NSA project for the development of secure mobile phones.

Security token
Unlike earlier equipment like STU-III (which needed a Crypto Ignition Key) and STE (which needed a crypto card), SCIP devices do not use an physical security token. Instead, the use of the secure mode of the device is protected with a Personal Identification Number (PIN) of 7 digits for Type 1 security or 4 digits for unclassified communication [1].

Key exchange
When negotiating a Traffic Encryption Key (TEK), an enhanced FIREFLY messaging system is used for key exchange. FIREFLY is an NSA-developed key management system based on public key cryptography (PKC).

SCIP can work with a wide variety of Voice Coders, or vocoders, which are negotiated during call setup. As a minimum requirment, all SCIP compatible devices must at least support eMELP — Enhanced Mixed-Excitation Linear Prediction. Compared to the older MELP vocoder, eMELP offers additional preprocessing, analyzer and synthesizer capabilities for improved intelligibility and noise robustness. MELP anbd MELPe are interoperable at 2400 bps, sending a 54 bit data frame every 22.5 ms. In addition, MELPe can also be used at 1200 bps and 600 bps.

SCIP can work with a variety of cryptographic algorithms. In Multinational Mode, all SCIP compatible devices must at least support the Advanced Encryption Standard (AES). In US National Mode, the BATON encryption algorithm is used. Other nations have developed their own encryption algorithms for SCIP.

  1. Wikipedia, SCIP
    Secure Communications Interoperability Protocol

  2. Nato C3 Agency, Introduction to FNBDT
    Retrieved from website, December 2011.

  3. Information Assurance Directorate, SCIP Documentation
    US Government. Visited 14 November 2022.
Further information
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Crypto Museum. Last changed: Monday, 14 November 2022 - 09:49 CET.
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