NSA encryption systems


The National Security Agency took over responsibility for all U.S. Government encryption systems when it was formed in 1952. The technical details of most NSA-approved systems are still classified, but much more about its early systems have become known and its most modern systems share at least some features with commercial products.
Rotor machines from the 1940s and 1950s were mechanical marvels. The first generation electronic systems were quirky devices with cantankerous punched card readers for loading keys and failure-prone, tricky-to-maintain vacuum tube circuitry. Late 20th century systems are just black boxes, often literally. In fact they are called blackers in NSA parlance because they convert plaintext classified signals into encrypted unclassified ciphertext signals. They typically have electrical connectors for the red signals, the black signals, electrical power, and a port for loading keys. Controls can be limited to selecting between key fill, normal operation, and diagnostic modes and an all important zeroize button that erases classified information including keys and perhaps the encryption algorithms. 21st century systems often contain all the sensitive cryptographic functions on a single, tamper-resistant integrated circuit that supports multiple algorithms and allows over-the-air or network re keying, so that a single hand-held field radio, such as the AN/PRC-148 or AN/PRC-152, can interoperate with most current NSA cryptosystems.

Security factors

NSA has to deal with many factors in ensuring the security of communication and information :
The large number of encryption systems that NSA has developed in its half century of operation can be grouped into five generations :

First generation: electromechanical

First generation NSA systems were introduced in the 1950s and were built on the legacy of NSA's World War II predecessors and used rotor machines derived from the SIGABA design for most high level encryption; for example, the KL-7. Key distribution involved distribution of paper key lists that described the rotor arrangements, to be changed each day at midnight, GMT. The highest level traffic was sent using one-time tape systems, including the British 5-UCO, that required vast amounts of paper tape keying material.

Second generation: vacuum tubes

Second generation systems were all electronic designs based on vacuum tubes and transformer logic. Algorithms appear to be based on linear feedback shift registers, perhaps with some non-linear elements thrown in to make them more difficult to cryptanalyze. Keys were loaded by placing a punched card in a locked reader on the front panel. The cryptoperiod was still usually one day. These systems were introduced in the late 1960s and stayed in use until the mid-1980s. They required a great deal of care and maintenance, but were not vulnerable to EMP. The discovery of the Walker spy ring provided an impetus for their retirement, along with remaining first generation systems.

Third generation: integrated circuits

Third generation systems were transistorized and based on integrated circuits and likely used stronger algorithms. They were smaller and more reliable. Field maintenance was often limited to running a diagnostic mode and replacing a complete bad unit with a spare, the defective box being sent to a depot for repair. Keys were loaded through a connector on the front panel. NSA adopted the same type of connector that the military used for field radio handsets as its fill connector. Keys were initially distributed as strips of punched paper tape that could be pulled through a hand held reader connected to the fill port. Other, portable electronic fill devices were available as well.

Fourth generation: electronic key distribution

Fourth generation systems use more commercial packaging and electronic key distribution. Integrated circuit technology allowed backward compatibility with third generation systems. Security tokens, such as the KSD-64 crypto ignition key were introduced. Secret splitting technology allows encryptors and CIKs to be treated as unclassified when they were separated. Later the Fortezza card, originally introduced as part of the controversial Clipper chip proposal, were employed as tokens. Cryptoperiods were much longer, at least as far as the user was concerned. Users of secure telephones like the STU-III only have to call a special phone number once a year to have their encryption updated. Public key methods were introduced for electronic key management. Keys could now be generated by individual commands instead of coming from NSA by courier. A common handheld fill device was introduced to replace the plethora of devices used to load keys on the many third generation systems that were still widely used. Encryption support was provided for commercial standards such as Ethernet, IP, and optical fiber multiplexing. Classified networks, such as SIPRNet and JWICS, were built using commercial Internet technology with secure communications links between "enclaves" where classified data was processed. Care had to be taken to ensure that there were no insecure connections between the classified networks and the public Internet.

Fifth generation: network-centric systems

In the twenty-first century, communication is increasingly based on computer networking. Encryption is just one aspect of protecting sensitive information on such systems, and far from the most challenging aspect. NSA's role will increasingly be to provide guidance to commercial firms designing systems for government use. HAIPE solutions are examples of this type of product. Other agencies, particularly NIST, have taken on the role of supporting security for commercial and sensitive but unclassified applications. NSA's certification of the unclassified NIST-selected AES algorithm for classified use "in NSA approved systems" suggests that, in the future, NSA may use more non-classified algorithms. The KG-245A and KG-250 use both classified and unclassified algorithms. The NSA Information Assurance Directorate is leading the Department of Defense Cryptographic Modernization Program, an effort to transform and modernize Information Assurance capabilities for the 21st century. It has three phases:
NSA has helped develop several major standards for secure communication: the Future Narrow Band Digital Terminal for voice communications, High Assurance Internet Protocol Interoperability Encryption- Interoperability Specification for computer networking and Suite B encryption algorithms.

NSA encryption by type of application

The large number of encryption systems that NSA has developed can be grouped by application:

Record traffic encryption

During World War II, written messages were encrypted off line on special, and highly secret, rotor machines and then transmitted in five letter code groups using Morse code or teletypewriter circuits, to be decrypted off-line by similar machines at the other end. The SIGABA rotor machine, developed during this era continued to be used until the mid-1950s, when it was replaced by the KL-7, which had more rotors.
The KW-26 ROMULUS was a second generation encryption system in wide use that could be inserted into teletypewriter circuits so traffic was encrypted and decrypted automatically. It used electronic shift registers instead of rotors and became very popular, with over 14,000 units produced. It was replaced in the 1980s by the more compact KG-84, which in turn was superseded by the KG-84-interoperable KIV-7.

Fleet broadcast

U.S. Navy ships traditionally avoid using their radios to prevent adversaries from locating them by direction finding. The Navy also needs to maintain traffic security, so it has radio stations constantly broadcasting a stream of coded messages. During and after World War II, Navy ships copied these fleet broadcasts and used specialized call sign encryption devices to figure out which messages were intended for them. The messages would then be decoded off line using SIGABA or KL-7 equipment.
The second generation KW-37 automated monitoring of the fleet broadcast by connecting in line between the radio receiver and a teleprinter. It, in turn, was replaced by the more compact and reliable third generation KW-46.

Strategic forces

NSA has the responsibility to protect the command and control systems for nuclear forces. The KG-3X series is used in the U.S. government's Minimum Essential Emergency Communications Network and the Fixed Submarine Broadcast System used for transmission of emergency action messages for nuclear and national command and control of U.S. strategic forces. The Navy is replacing the KG-38 used in nuclear submarines with KOV-17 circuit modules incorporated in new long-wave receivers, based on commercial VME packaging. In 2004, the U.S. Air Force awarded contracts for the initial system development and demonstration phase of a program to update these legacy generation systems used on aircraft.

Trunk encryption

Modern communication systems multiplex many signals into wideband data streams that are transmitted over optical fiber, coaxial cable, microwave relay, and communication satellites. These wide-band circuits require very fast encryption systems.
The WALBURN family of equipment consists of high-speed bulk encryption devices used primarily for microwave trunks, high-speed land-line circuits, video teleconferencing, and T-1 satellite channels. Another example is the KG-189, which support SONET optical standards up to 2.5 Gbit/s.
Digital Data encryptors such as KG-84 family which includes the TSEC/KG-84, TSEC/KG-84A and TSEC/KG-82, TSEC/KG-84A and TSEC/KG-84C, also the KIV-7.

Voice encryption

True voice encryption was pioneered during World War II with the 50-ton SIGSALY, used to protect the very highest level communications. It did not become practical for widespread use until reasonable compact speech encoders became possible in the mid-1960s. The first tactical secure voice equipment was the NESTOR family, used with limited success during the Vietnam war. Other NSA voice systems include:
The operational complexity of secure voice played a role in the September 11, 2001 attacks on the United States. According to the 911 Commission, an effective U.S. response was hindered by an inability to set up a secure phone link between the National Military Command Center and the Federal Aviation Administration personnel who were dealing with the hijackings. See Communication during the September 11, 2001 attacks.

Internet

NSA has approved a variety of devices for securing Internet Protocol communications. These have been used to secure the Secret Internet Protocol Router Network, among other uses.
The first commercial network layer encryption device was the Motorola Network Encryption System. The system used the SP3 and KMP protocols defined by the NSA Secure Data Network System and were the direct precursors to IPsec. The NES was built in a three part architecture that used a small cryptographic security kernel to separate the trusted and untrusted network protocol stacks.


The SDNS program defined a Message Security Protocol that was built on the use X.509 defined certificates. The first NSA hardware built for this application was the BBN Safekeeper. The Message Security Protocol was a precursor to the IETF Privacy Enhance Mail protocol. The BBN Safekeeper provided a high degree of tamper resistance and was one of the first devices used by commercial PKI companies.

Field authentication

NSA still supports simple paper encryption and authentication systems for field use such as DRYAD.

Public systems

NSA has participated in the development of several encryption systems for public use. These include: