encipher

Encipher is a verb in cryptography meaning to convert plaintext into ciphertext by applying a cipher or encryption algorithm and a key. The enciphered output is designed to be unreadable unless the recipient can perform the corresponding decryption operation. Encipherment is a central concept in protecting confidentiality for communications and data.

The term is often used interchangeably with encrypt, though some writing distinguishes encipherment as the act of applying an encipher transformation and encrypt as the broader practice, especially in contemporary technical usage where encrypt is more common. In many contexts the two are treated as synonymous.

Encipherment relies on a mathematical function and a key. In symmetric-key systems, the same secret key is used to encipher and decipher. In public-key (asymmetric) systems, a public key is used to encipher and a private key to decipher. The output of encipherment is ciphertext, which hides the original plaintext unless the correct key and algorithm are applied.

Classical examples of encipherment include substitution ciphers (for example, the Caesar shift) and transposition ciphers. Modern encipherment typically uses standardized algorithms such as AES for symmetric encryption or RSA and elliptic-curve methods for public-key encryption. The term remains widely used in historical discussions and certain formal or legal texts, though encrypt is common in many modern contexts.

Etymology: from Middle French encipherer, from cipher, from old French chifre, from Arabic sifr.