In cryptography, a cipher ( or cypher ) is an algorithm for performing encryption or decryption — a series of well-defined steps that can be followed as a procedure.

* symmetric key algorithms ( Private-key cryptography ), where the same key is used for encryption and decryption, and

* asymmetric key algorithms ( Public-key cryptography ), where two different keys are used for encryption and decryption.

Information security uses cryptography to transform usable information into a form that renders it unusable by anyone other than an authorized user ; this process is called encryption.

In cryptography, the one-time pad ( OTP ) is a type of encryption which has been proven to be impossible to crack if used correctly.

PGP encryption uses a serial combination of hashing, data compression, symmetric-key cryptography, and, finally, public-key cryptography ; each step uses one of several supported algorithms.

Since the 1970s, a large number and variety of encryption, digital signature, key agreement, and other techniques have been developed in the field of public-key cryptography.

Most were passionately opposed to various government attempts to limit cryptography — export laws, promotion of limited key length ciphers, and especially escrowed encryption.

In cryptography, a substitution cipher is a method of encryption by which units of plaintext are replaced with ciphertext, according to a regular system ; the " units " may be single letters ( the most common ), pairs of letters, triplets of letters, mixtures of the above, and so forth.

In cryptography, a transposition cipher is a method of encryption by which the positions held by units of plaintext ( which are commonly characters or groups of characters ) are shifted according to a regular system, so that the ciphertext constitutes a permutation of the plaintext.

In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques.

Symmetric-key algorithms are a class of algorithms for cryptography that use the same cryptographic keys for both encryption of plaintext and decryption of ciphertext.

In cryptography, the ElGamal encryption system is an asymmetric key encryption algorithm for public-key cryptography which is based on the Diffie – Hellman key exchange.

Chosen-plaintext attacks become extremely important in the context of public key cryptography, where the encryption key is public and attackers can encrypt any plaintext they choose.

In cryptography, obfuscation refers to encoding the input data before it is sent to a hash function or other encryption scheme.

A block cipher is one of the most basic primitives in cryptography, and frequently used for data encryption.

In the history of cryptography, the ECM Mark II was a cipher machine used by the United States for message encryption from World War II until the 1950s.

In cryptography, ciphertext ( or cyphertext ) is the result of encryption performed on plaintext using an algorithm, called a cipher.

The history of cryptography begins thousands of years ago and contains a variety of different types of encryption.

* Private-key cryptography ( symmetric key algorithm ): the same key is used for encryption and decryption

The latter is more cumbersome to use, so it's only employed when necessary, for example in the analysis of arbitrary-precision arithmetic algorithms, like those used in cryptography.

In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called blocks, with an unvarying transformation that is specified by a symmetric key.

In non-technical usage, a " cipher " is the same thing as a " code "; however, the concepts are distinct in cryptography.

In cryptography, key size or key length is the size measured in bits of the key used in a cryptographic algorithm ( such as a cipher ).

It is one of the earliest practical examples of key exchange implemented within the field of cryptography.

The introduction of DES is considered to have been a catalyst for the academic study of cryptography, particularly of methods to crack block ciphers.

" An astonishing share of the open literature in cryptography in the 1970s and 1980s dealt with the DES, and the DES is the standard against which every symmetric key algorithm since has been compared.

Elliptic curve cryptography ( ECC ) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields.

Public-key cryptography is based on the intractability of certain mathematical problems.

Elliptic curve cryptography is vulnerable to a modified Shor's algorithm for solving the discrete logarithm problem on elliptic curves.

The result of the process is information ( in cryptography, referred to as ciphertext ).

Factorization of large integers is believed to be a computationally very difficult problem, and the security of many modern cryptography systems is based upon its infeasibility.

The Communications-Electronics Security Group ( CESG ) of GCHQ provides assistance to government departments on their own communications security: CESG is the UK national technical authority for information assurance, including cryptography.

Although related, the distinctions among these measures mean that a random variable with high Shannon entropy is not necessarily satisfactory for use in an extractor and so for cryptography uses.

In cryptography, the International Data Encryption Algorithm ( IDEA ) is a block cipher designed by James Massey of ETH Zurich and Xuejia Lai and was first described in 1991.

The presumed difficulty of this problem is at the heart of widely used algorithms in cryptography such as RSA.

This will have significant implications for cryptography if a large quantum computer is ever built.

The problem often arises in resource allocation where there are financial constraints and is studied in fields such as combinatorics, computer science, complexity theory, cryptography and applied mathematics.

* MARS ( cryptography ), a block cipher that was IBM's submission to the Advanced Encryption Standard process.

In public key cryptography, padding is the process of preparing a message for encryption or signing using a specification or scheme such as PKCS # 1 v2. 0, OAEP, PSS, PSSR, IEEE P1363 EMSA2 and EMSA5.

In cryptography, the Generalized DES Scheme ( GDES or G-DES ) is a variant of the DES block cipher designed with the intention of speeding up the encryption process while improving its security.

* Ancillary cryptography items are the ones primarily used not for computing and communications, but for digital right management ; games, household appliances ; printing, photo and video recording ( but not videoconferencing ); business process automation ; industrial or manufacturing systems ( including robotics, fire alarms and HVAC ); automotive, aviation and other transportation systems.

The NSA describes Bamford's research process in a partially declassified history of postwar American cryptography.

Key generation is the process of generating keys for cryptography.

Typically a hardware SSL accelerator will offload processing of the SSL handshake while leaving the server software to process the less intense symmetric cryptography of the actual SSL data exchange, but some accelerators handle all SSL operations and terminate the SSL connection, thus leaving the server seeing only unencrypted connections.

In cryptography, a message authentication code based on universal hashing, or UMAC, is a type of message authentication code ( MAC ) calculated choosing a hash function from a class of hash functions according to some secret ( random ) process and applying it to the message.