STU-III - AbsoluteAstronomy.com

STU-III is a family of secure telephone

Telephone

The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...

s introduced in 1987 by the NSA for use by the United States government, its contractors, and its allies. STU-III desk units look much like typical office telephones, plug into a standard telephone wall jack and can make calls to any ordinary phone user (such calls receiving, however, no special protection). However, when a call is placed to another STU-III unit that is properly set up, one caller can ask the other to initiate secure transmission

Secure transmission

In computer science, Secure Transmission refers to the transfer of data such as confidential or proprietary information over a secure channel. Many secure transmission methods require a type of encryption. The most common email encryption is called PKI...

(or, colloquially, to "go secure"). They then press a button on their telephones and, after a 15 second delay, their call is encrypted to prevent eavesdropping. There are portable and militarized versions and most STU-IIIs contain an internal modem

Modem

A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...

and RS-232

RS-232

In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...

port for data and fax

Fax

Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

transmission.
Vendors were AT&T (later transferred to Lucent Technologies), RCA (Now L3-Communications, East); and Motorola.

Versions

STU-III/Low Cost Terminal (LCT) designed for use in office environment by all types of users. (Motorola Sectel 1500, Lucent Technologies/GD 1100 and 1150)
STU-III/Cellular Telephone (CT) is interoperable with all STU-III versions. Works in all continental US mobile network and in most of the foreign cellular networks.
STU-III/Allied (A) specialized version of the STU-III/LCT that is compatible with the STU-II. It retains all basic STU-III functions and capabilities and incorporates STU-II BELLFIELD KDC, STU-II net, and STU-II multipoint modes of operation.
STU-III/Remote Control Interface (R or RCU)
STU-III/MultiMedia Terminal (MMT)
STU-III/Inter Working Function (IWF)
STU-III/Secure Data Device (SDD)
STU-III/CipherTAC 2000 (CTAC)

Security

Most STU-III units were built for use with what NSA calls Type 1 encryption

Type 1 encryption

In cryptography, a Type 1 product is a device or system certified by the National Security Agency for use in cryptographically securing classified U.S...

. This allows them to protect conversations at all security classification levels up to Top Secret

Classified information in the United States

The United States government classification system is currently established under Executive Order 13526, the latest in a long series of executive orders on the topic. Issued by President Barack Obama in 2009, Executive Order 13526 replaced earlier executive orders on the topic and modified the...

, with the maximum level permitted on a call being the lower clearance level of the two persons talking. At the height of the Commercial COMSEC Endorsement Program, Type 2

Type 2 encryption

In cryptography, Type 2 products are unclassified cryptographic equipment, assemblies, or components, endorsed by the National Security Agency , for use in telecommunications and automated information systems for the protection of national security information.Note: The term refers only to...

, 3

Type 3 encryption

In NSA terminology, a Type 3 product is a device for use with Sensitive, But Unclassified information on non-national security systems. Approved algorithms include DES, Triple DES, and AES .-See also:* Type 1 product* Type 2 product* Type 4 product* NSA Suite B Cryptography* NSA Suite A Cryptography...

, and 4

Type 4 encryption

In NSA terminology, a Type 4 algorithm is an encryption algorithm that has been registered with NIST but is not a Federal Information Processing Standard...

STU-IIIs were manufactured, but they saw little commercial success.

Two major factors in the STU-III's success were the Electronic Key Management System (EKMS) and the use of a removable memory module in a plastic package in the shape of a house key, called a KSD-64A. The EKMS is believed to be one of the first widespread applications of asymmetric cryptography. It greatly reduced the complex logistics and bookkeeping associated with ensuring each encryption

Encryption

In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...

device has the right keys and that all keying material is protected and accounted for.

The KSD-64A contains a 64kbit EEPROM

EEPROM

EEPROM stands for Electrically Erasable Programmable Read-Only Memory and is a type of non-volatile memory used in computers and other electronic devices to store small amounts of data that must be saved when power is removed, e.g., calibration...

chip that can be used to store various types of keying and other information. A new (or zeroized

Zeroisation

In cryptography, zeroisation is the practice of erasing sensitive parameters from a cryptographic module to prevent their disclosure if the equipment is captured. This is generally accomplished by altering or deleting the contents to prevent recovery of the data...

) STU-III must first have a "seed key" installed. This key is shipped from NSA by registered mail

Registered mail

Registered mail describes letters, packets or other postal documents considered valuable and need a chain of custody that provides more control than regular mail. The posted item has its details recorded in a register to enable its location to be tracked, sometimes with added insurance to cover loss...

or Defense Courier Service

Defense Courier Service

The Defense Courier Service is established under the United States Transportation Command , and is a global courier network for the expeditious, cost-effective, and secure distribution of highly classified and sensitive material. Operational control of global courier activities is exercised...

. Once the STU-III has its seed key, the user calls an 800-number at NSA to have the seed key converted into an operational key. A list of compromised keys is downloaded to the STU-III at this time. The operational key is supposed to be renewed at least once a year.

The operational key is then split into two components, one of which replaces the information on the KSD-64A, at which point it becomes a Crypto Ignition Key or CIK. When the CIK is removed from the STU-III telephone neither unit is considered classified. Only when the CIK is inserted into the STU-III on which it was created can classified information be received and sent.

When a call "goes secure," the two STU-III's create a unique key that will be used to encrypt just this call. Each unit first makes sure that the other is not using a revoked key and if one has a more up-to-date key revocation list it transmits it to the other. Presumably the revocation lists are protected by a digital signature

Digital signature

A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit...

generated by NSA.

While there have been no reports of STU-III encryption being broken, there have been claims that foreign intelligence services can recognize the lines on which STU-IIIs are installed and that un-encrypted calls on these lines, particularly what was said while waiting for the "go secure" command to complete, have provided valuable information.

Use

Hundreds of thousands of STU-III sets were produced and many are still in use as of 2004. STU-III replaced earlier voice encryption devices, including the KY-3

KY-3

The KY-3 is a secure telephone system developed by the U.S. National Security Agency in the early 1960s. The "TSEC" prefix to the model number indicates NSA's Telecommunications Security nomenclature system...

(1960s), the STU-I

STU-I

The STU-I, like its successors sometimes known as a "stew phone", was a secure telephone developed by the U.S. National Security Agency for use by senior U.S. government officials in the 1970s.-External links:*-See also:*KY-3*Navajo I*STU-II...

(1970) and the STU-II

STU-II

The STU-II is a secure telephone developed by the U.S. National Security Agency. It permitted up to six users to have secure communications, on a time-shared basis. It was made by ITT Defense Communications, Nutley, New Jersey...

(1975). The STU-II had some 10,000 users. These, in turn, replaced less secure voice scrambler

Scrambler

In telecommunications, a scrambler is a device that transposes or inverts signals or otherwise encodes a message at the transmitter to make the message unintelligible at a receiver not equipped with an appropriately set descrambling device...

s. Unlike earlier systems, the STU-III's encryption electronics are completely contained in the desk set. The STU-III is no longer in production, and is being replaced by the STE (Secure Terminal Equipment

Secure Terminal Equipment

Secure Terminal Equipment is the U.S. Government's current , encrypted telephone communications system for wired or "landline" communications. STE is designed to use ISDN telephone lines which offer higher speeds of up to 128k bits per second and are all digital...

) or OMNI

OMNI (SCIP)

The OMNI adds Type 1 secure voice and secure data to any standard analog telephone or modem connected computer. SCIP signalling allows interoperability with other SCIP devices such as the Secure Terminal Equipment phone...

, more modern, all digital systems that overcome many of the STU-III's problems, including the 15 second delay.

STE succeeded STU-III in the 1990s. Similar to STU-III, an STE unit physically resembles an ordinary telephone. Besides connecting to a regular wall phone jack (Public Switched Telephone Network

Public switched telephone network

The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...

), the STE was originally designed to be connected to Integrated Services Digital Network

Integrated Services Digital Network

Integrated Services Digital Network is a set of communications standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network...

(ISDN) lines. As a result, in addition to having secured voice conversations, users can also use an STE unit for classified data and fax transmissions. Transfer rate of an STE is also considerably higher (STU-III: up to 9 kbit/s; STE: up to 128 kbit/s). Lastly, an STE unit is backward compatible with an STU-III unit when both units are connected to the PSTN.

The heart of an STE unit is the Fortezza Plus (KOV-14

KOV-14

The KOV-14 Fortezza Plus is a US National Security Agency-approved PC card which provides encryption functions and key storage to the Secure Terminal Equipment and other devices...

) Crypto Card, which is a PCMCIA card. It contains both the cryptographic algorithms as well as the key(s) used for encryption. Cryptographic algorithms include BATON, FIREFLY, and SDNS signature algorithm. When the Crypto Card is removed from the STE unit, neither the phone or the card is considered classified. BATON is a block cipher developed by the NSA with a block size of 128 bits and key size of 320 bits. FIREFLY, on the other hand, is a key distribution protocol developed by the NSA. The FIREFLY protocol uses public key cryptography to exchange keys between two participants of a secured call.

Both STU-III and STE are built on technologies that are proprietary, and detail of the cryptographic algorithms is classified (e.g. BATON, FIREFLY). Although the secrecy of the algorithms does not make the device less secure, it does limit the usage to within the U.S. military. The concept of secured voice application is nothing new to the commercial world. Synchronous transmission of confidential information is often necessary for the operation of a business. Many corporations have resorted to the more-available Voice Over IP

Voice over IP

Voice over Internet Protocol is a family of technologies, methodologies, communication protocols, and transmission techniques for the delivery of voice communications and multimedia sessions over Internet Protocol networks, such as the Internet...

(VOIP) technology. However, security of VOIP calls has been limited to compression to make eavesdropping difficult, security by obscurity, and encryption/cryptographic authentication which is not widely available. Within the Department of Defense, VOIP has slowly emerged as an alternative solution to STU-III and STE. The high bandwidth of IP networks makes VOIP attractive because it results in superior voice quality over STU-III and STE. To secure VOIP calls, VOIP phones are connected to classified IP networks (e.g. Secret Internet Protocol Router Network – SIPRNET

SIPRNet

The Secret Internet Protocol Router Network is "a system of interconnected computer networks used by the United States Department of Defense and the U.S. Department of State to transmit classified information by packet switching over the TCP/IP protocols in a 'completely secure' environment"...

).

Both allies and adversaries of the United States are interested in STU-III, STE, and other secured voice technologies developed by the NSA. To date, there has not been any reported cryptanalysis

Cryptanalysis

Cryptanalysis is the study of methods for obtaining the meaning of encrypted information, without access to the secret information that is normally required to do so. Typically, this involves knowing how the system works and finding a secret key...

on the encryption algorithms used by the STU-III and STE. Any breaks in these algorithms could jeopardize national security

National security

National security is the requirement to maintain the survival of the state through the use of economic, diplomacy, power projection and political power. The concept developed mostly in the United States of America after World War II...

and, potentially, threaten the lives of citizens both in the United States and allied countries.

Because of the sensitive nature of the subject, there are few relevant documents available on the Internet. The war on terrorism has caused many government agencies to remove any potentially-sensitive information from their websites in the public domain. During the course of research, the majority of the information originates from the manufacturers (e.g. L-3 Communications) of STU-III and STE. As mentioned earlier, the detail of the cryptographic algorithms is considered classified, and is therefore not available. Information about STU-III is very limited despite the fact that it is out of production.

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.