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A key is a piece of information that controls the operation of a cryptography algorithm. In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa during decryption. Keys are also used in other cryptographic algorithms, such as digital signature schemes and keyed-hash functions (also known as MACs), often used for authentication. Cryptography (from Greek kryptós, hidden, and gráphein, to write) is, traditionally, the study of means of converting information from its normal, comprehensible form into an incomprehensible format, rendering it unreadable without secret knowledge — the art of encryption. ...
In cryptography, encryption is the process of obscuring information to make it unreadable without special knowledge. ...
In cryptography, plaintext is information used as input to an encryption algorithm; the output is termed ciphertext. ...
This article is about algorithms for encryption and decryption. ...
This article is about algorithms for encryption and decryption. ...
Digital signatures are a method of authenticating digital information analogous to ordinary physical signatures on paper, but implemented using techniques from the field of cryptography. ...
In cryptography, a message authentication code (MAC) is a short piece of information used to authenticate a message. ...
In computer security, authentication (Greek: αυθεντικός, from authentes=author) is the process by which a computer, computer program, or another user attempts to confirm that the computer, computer program, or user from whom the second party has received some communication is, or is not, the claimed first party. ...
For a well-designed algorithm, enciphering the same plaintext but with a different key should produce a totally different ciphertext. Similarly, decrypting ciphertext with the wrong key should produce random-looking gibberish. (For deniable encryption, 2 keys can produce 2 very different normal-looking plaintexts). If the decryption key is lost, encrypted data should not in practice be recoverable — at least for high quality encryption algorithms and large enough key sizes. In cryptography, deniable encryption allows an encrypted message to be decrypted to different plaintexts, depending on the key used. ...
Need for secrecy In designing security systems, it is wise to assume that the details of the cryptographic algorithm are already available to the attacker. This principle is known as Kerckhoffs' law — "only secrecy of the key provides security", or "the enemy knows the system". The history of cryptography provides evidence that it can be difficult to keep the details of a widely-used algorithm secret. A key is often easier to protect (it's typically a small piece of information) than an encryption algorithm, and easier to change if compromised. Thus, the security of an encryption system in most cases relies on some key being kept secret. In cryptography, Kerckhoffs law (also called Kerckhoffs assumption, axiom or principle) was stated by Auguste Kerckhoffs in the 19th century: a cryptosystem should be secure even if everything about the system, except the key, is public knowledge. ...
The history of cryptography dates back thousands of years, and for the most part, it has been the history of classical cryptography; that is, methods of encryption which can be performed using pen and paper (or perhaps with simple mechanical aids). ...
Secrecy is the condition of hiding information from others. ...
Keeping keys secret is one of the most difficult problems in practical cryptography; see key management. An attacker who obtains the key (by, for example, theft, extortion, dumpster diving, social engineering or inspection of a Post-it note stuck to the side of a terminal) can recover the original message from the encrypted data. In cryptography, key management includes all of the provisions made in a cryptosystem design, in cryptographic protocols in that design, in user procedures, and so on, which are related to generation, exchange, storage, safeguarding, use, vetting, and replacement of keys. ...
Dumpster diving is the practice of rummaging through trash, whether commercial or residential, to find items of use that have been discarded. ...
In the field of computer security, social engineering is the practice of obtaining confidential information by manipulation of legitimate users. ...
A number of Post-it notes still glued together A Post-it note (or just Post-it) is a piece of stationery designed for temporarily attaching notes to documents, computer displays and so forth. ...
Encryption algorithms which use the same key for both encryption and decryption are known as symmetric key algorithms. A newer class of "public key" cryptographic algorithms was discovered in the 1970s which use a pair of keys, one to encrypt and one to decrypt. These asymmetric key algorithms allows one key to be made public while retaining the private key in only one location. They are designed so that finding out the private key is difficult or impossible, even if the corresponding public key is known. A user of public key technology can publish their public key, while keeping their private key secret, allowing anyone to send them an encrypted message. A symmetric-key algorithm is an algorithm for cryptography that uses the same cryptographic key to encrypt and decrypt the message. ...
Events and trends Although in the United States and in many other Western societies the 1970s are often seen as a period of transition between the turbulent 1960s and the more conservative 1980s and 1990s, many of the trends that are associated widely with the Sixties, from the Sexual Revolution...
In cryptography, an asymmetric key algorithm uses a pair of cryptographic keys to encrypt and decrypt. ...
Key sizes - Main article: Key size
For the one time pad system the key must be at least as long as the message. In encryption systems that use a cipher algorithm, messages can be much longer than the key. The key must, however, be long enough so that an attacker cannot try all possible combinations. In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ...
In cryptography, the one-time pad (OTP), is a theoretically unbreakable method of encryption where the plaintext is combined with a random pad the same length as the plaintext. ...
This article is about algorithms for encryption and decryption. ...
A key length of 80 bits is generally considered the minimum for strong security with symmetric encryption algorithms. 128-bit keys are commonly used and considered very strong. See the key size article for a fuller discussion. In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ...
The keys used in public key cryptography have some mathematical structure. For example, public keys used in the RSA system are the product of two prime numbers. Thus public key systems require longer key lengths than symmetric systems for an equivalent level of security. 3072 bits is the suggested key length for systems based on factoring and integer discrete logarithms which aim to have security equivalent to a 128 bit symmetric cipher. Elliptic curve cryptography may allow smaller-size keys for equivalent security, but these algorithms have only been known for a relatively short time and current estimates of the difficulty of searching for their keys may not survive. Recently, a message encrypted using a 109-bit key elliptic curve algorithm was broken by brute force. The current rule of thumb is to use an ECC key twice as long as the symmetric key security level desired. Except for the random one-time pad, the security of these systems has not (as of 2004) been proven mathematically, so a theoretical breakthrough could make everything you've encrypted an open book. This is another reason to err on the side of choosing longer keys. PKC, see PKC (disambiguation) Public-key cryptography is a form of modern cryptography which allows users to communicate securely without previously agreeing on a shared secret key. ...
In cryptography, RSA is an algorithm for public key encryption. ...
This article is about the mathematical concept. ...
In abstract algebra and its applications, the discrete logarithms are defined in group theory in analogy to ordinary logarithms. ...
Elliptic curve cryptography (ECC) is an approach to public-key cryptography based on the mathematics of elliptic curves. ...
In cryptography, the one-time pad (OTP) is the only theoretically unbreakable method of encryption: the plaintext is combined with a random pad the same length as the plaintext. ...
2004 is a leap year starting on Thursday of the Gregorian calendar. ...
Key choice To prevent a key from being guessed, keys need to be generated randomly and contain sufficient entropy. The problem of how to safely generate truly random keys is difficult, and has been addressed in many ways by various cryptographic systems. There is a RFC on generating randomness (RFC 1750, Randomness Recommendations for Security). Some operating systems include tools for "collecting" entropy from the timing of unpredictable operations such as disk drive head movements. For the production of small amounts of keying material, ordinary dice provide a good source of high quality randomness. In ordinary language, the word random is used to express apparent lack of purpose or cause. ...
The thermodynamic entropy S, often simply called the entropy in the context of thermodynamics, is a measure of the amount of energy in a physical system that cannot be used to do work. ...
Alternate meaning: Wikipedia:Requests for comment A Request for Comments (RFC) document is one of a series of numbered Internet informational documents and standards very widely followed by both commercial software and freeware in the Internet and Unix communities. ...
Disk Drive is the afternoon show on CBC Radio Two. ...
Rolling dice A die (Old French de, from Latin datum something given or played [1]) is a small polyhedral object (usually a cube) suitable as a gambling device (especially for craps). ...
When a password (or passphrase) is used as an encryption key, well-designed cryptosystems first run it through a key-derivation algorithm which adds salt and reduces or expands it to the key length desired, for example by reducing a long phrase into a 128-bit value suitable for use in a block cipher. A password is a form of authentication which uses secret data to control access to a resource. ...
In cryptography, salt consists of random bits (typically 12 or more) used as one of the inputs to a key derivation function. ...
In cryptography, a block cipher is a type of symmetric key cipher which operates on groups of bits of a fixed length, termed blocks. ...
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