ciphering

Ciphering is the process of transforming plaintext into ciphertext using a cipher, with the aim of concealing the content from unauthorized readers. A cipher is an algorithm that defines how each element of plaintext is replaced or permuted to produce ciphertext, and a key is a parameter that governs that transformation. Deciphering is the reverse operation, recovering the original message using the same or a related key.

There are two broad categories of ciphering: symmetric (secret-key) and asymmetric (public-key). In symmetric ciphering, the same key encrypts and decrypts data. In asymmetric ciphering, one key encrypts and a different key decrypts, typically a public key for encryption and a private key for decryption. Ciphers can also be classified by method, such as substitutions, transpositions, or a combination of both. Classic examples include monoalphabetic substitutions and transposition ciphers; modern examples include block ciphers (AES, DES) and stream ciphers (ChaCha20), as well as public-key schemes (RSA, ECC).

Security relies on the strength of the algorithm, key length, and proper use. Potential issues include cryptanalysis, weak or reused keys, insecure modes of operation, and implementation flaws. Good practice emphasizes long, random keys; appropriate padding and modes; and secure key management.

Ciphering is fundamental to modern cryptography and underpins secure communications, data protection, and authentication. It is used in protocols such as TLS, email encryption with PGP, and digital signatures to ensure confidentiality, integrity, and authenticity.