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. An alternative, less common term is encipherment. To encipher or encode is to convert information from plain text into code or cipher. In non-technical usage, a “cipher” is the same thing as a “code”; however, the concepts are distinct in cryptography. In classical cryptography, ciphers were distinguished from codes. Codes operated by substituting according to a large codebook which linked a random string of characters or numbers to a word or phrase. For example, “UQJHSE” could be the code for “Proceed to the following coordinates”. When using a cipher the original information is known as plaintext, and the encrypted form as ciphertext. The ciphertext message contains all the information of the plaintext message, but is not in a format readable by a human or computer without the proper mechanism to decrypt it; it should resemble random gibberish to those not intended to read it.

In cryptography, encryption is the process of transforming information (referred to as plaintext) using an algorithm (called a cipher) 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 (in cryptography, referred to as ciphertext). The reverse process, i.e., to make the encrypted information readable again, is referred to as decryption (i.e., to make it unencrypted).

Verschlüsselung nennt man den Vorgang, bei dem ein klar lesbarer Text (Klartext) (oder auch Informationen anderer Art, wie Ton- oder Bildaufzeichnungen) mit Hilfe eines Verschlüsselungsverfahrens (Kryptosystem) in eine „unleserliche“, das heißt nicht einfach interpretierbare Zeichenfolge (Geheimtext) umgewandelt wird. Als entscheidend wichtige Parameter der Verschlüsselung werden hierbei ein oder auch mehrere Schlüssel verwendet.

Le chiffrement, parfois appelé cryptage, est en cryptographie le procédé grâce auquel on souhaite rendre la compréhension d'un document impossible à toute personne qui n'a pas la clé de (dé)chiffrement.

Kryptering är att göra information svårläslig för alla som inte ska kunna läsa den. För att göra informationen läslig igen krävs dekryptering.

Szyfr to rodzaj kodu, system umownych znaków stosowany w celu utajnienia wiadomości, żeby była ona niemożliwa (lub bardzo trudna) do odczytania przez każdego, kto nie posiada odpowiedniego klucza.