A cryptoperiod is the time span during which a specific cryptographic key is authorized for use. Common government guidelines [1] range from 1 to 3 years for asymmetric cryptography, [2] and 1 day to 7 days for symmetric cipher traffic keys. [3]
Factors to consider include the strength of the underlying encryption algorithm, key length, the likelihood of compromise through a security breach and the availability of mechanisms of revoking keys.
In traditional cryptographic practice, keys were changed at regular intervals, typically at the same time each day. The code word for a key change, in NSA parlance, is HJ or Hotel Juliet in the NATO phonetic alphabet. [4] [5]
When cryptographic devices began to be used in large scale, those who had to update the key had to set a specific time to synchronize the re-key. This was accomplished at the hour (H) the Julian (J) Date changed, among crypto-accountants, managers and users the jargon "HJ" became the accepted term meaning it was time to change the crypto-key.[ citation needed ]
During the Vietnam War, the United States issued its forces a series of secure voice encryption equipment code-named NESTOR. According to a U.S. Army history: "To maintain compatibility, key changes had to occur simultaneously in all units. The time chosen for this change was midnight, tactically the worst possible time because the greatest number of enemy contacts occurred from 2200 to 0200. Moreover, where several units shared the same keying device, having to move at night to change key settings was inconvenient and dangerous and added to the reasons for not using the equipment. Later the time of the daily NESTOR key change was moved to 0600." [6]
In cryptography, key size or key length refers to the number of bits in a key used by a cryptographic algorithm.
The Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data. Although its short key length of 56 bits makes it too insecure for modern applications, it has been highly influential in the advancement of cryptography.
In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decipher a ciphertext back to plaintext and access the original information. Encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor.
Communications security is the discipline of preventing unauthorized interceptors from accessing telecommunications in an intelligible form, while still delivering content to the intended recipients.
The U.S. National Security Agency (NSA) used to rank cryptographic products or algorithms by a certification called product types. Product types were defined in the National Information Assurance Glossary which used to define Type 1, 2, 3, and 4 products. The definitions of numeric type products have been removed from the government lexicon and are no longer used in government procurement efforts.
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. A block cipher by itself is only suitable for the secure cryptographic transformation of one fixed-length group of bits called a block. A mode of operation describes how to repeatedly apply a cipher's single-block operation to securely transform amounts of data larger than a block.
Cryptography, the use of codes and ciphers to protect secrets, began thousands of years ago. Until recent decades, it has been the story of what might be called classical cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids. In the early 20th century, the invention of complex mechanical and electromechanical machines, such as the Enigma rotor machine, provided more sophisticated and efficient means of encryption; and the subsequent introduction of electronics and computing has allowed elaborate schemes of still greater complexity, most of which are entirely unsuited to pen and paper.
Key management refers to management of cryptographic keys in a cryptosystem. This includes dealing with the generation, exchange, storage, use, crypto-shredding (destruction) and replacement of keys. It includes cryptographic protocol design, key servers, user procedures, and other relevant protocols.
STU-III is a family of secure telephones 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. 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. 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 contained an internal modem and RS-232 port for data and fax transmission. Vendors were AT&T, RCA and Motorola.
The export of cryptography from the United States to other countries has experienced various levels of restrictions over time. World War II illustrated that code-breaking and cryptography can play an integral part in national security and the ability to prosecute war. Changes in technology and the preservation of free speech have been competing factors in the regulation and constraint of cryptographic technologies for export.
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.
This glossary lists types of keys as the term is used in cryptography, as opposed to door locks. Terms that are primarily used by the U.S. National Security Agency are marked (NSA). For classification of keys according to their usage see cryptographic key types.
The vast majority of the National Security Agency's work on encryption is classified, but from time to time NSA participates in standards processes or otherwise publishes information about its cryptographic algorithms. The NSA has categorized encryption items into four product types, and algorithms into two suites. The following is a brief and incomplete summary of public knowledge about NSA algorithms and protocols.
A hardware security module (HSM) is a physical computing device that safeguards and manages secrets, performs encryption and decryption functions for digital signatures, strong authentication and other cryptographic functions. These modules traditionally come in the form of a plug-in card or an external device that attaches directly to a computer or network server. A hardware security module contains one or more secure cryptoprocessor chips.
A fill device or key loader is a module used to load cryptographic keys into electronic encryption machines. Fill devices are usually hand held and electronic ones are battery operated.
Cryptography, or cryptology, is the practice and study of techniques for secure communication in the presence of adversarial behavior. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, information security, electrical engineering, digital signal processing, physics, and others. Core concepts related to information security are also central to cryptography. Practical applications of cryptography include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications.
Attempts, unofficially dubbed the "Crypto Wars", have been made by the United States (US) and allied governments to limit the public's and foreign nations' access to cryptography strong enough to thwart decryption by national intelligence agencies, especially the National Security Agency (NSA).
NESTOR was a family of compatible, tactical, wideband secure voice systems developed by the U.S. National Security Agency and widely deployed during the Vietnam War through the late Cold War period of the 1980s. NESTOR consists of three systems. The KY-8 was used in vehicular and afloat applications; the KY-28 was the airborne version; and the KY-38 was the portable or man-pack model. About 30,000 NESTOR equipments were produced prior to their replacement by the VINSON secure voice family.
The IBM 4767 PCIe Cryptographic Coprocessor is a hardware security module (HSM) that includes a secure cryptoprocessor implemented on a high-security, tamper resistant, programmable PCIe board. Specialized cryptographic electronics, microprocessor, memory, and random number generator housed within a tamper-responding environment provide a highly secure subsystem in which data processing and cryptography can be performed. Sensitive key material is never exposed outside the physical secure boundary in a clear format.