cyphers

Cyphers, also spelled ciphers in some contexts, are methods for transforming information to protect confidentiality. A cipher defines the algorithm used to convert plaintext into ciphertext, while a key selects a particular instance of the transformation. In practice, encryption is the overall process of turning readable data into unreadable form, and the cipher is the mechanism by which that transformation is carried out. The same cipher can produce different results with different keys.

History and types. Early ciphers relied on substitutions or transpositions to disguise messages. Substitution ciphers replace units such as letters, while transposition ciphers rearrange them. Classic examples include the Caesar cipher and various columnar or rail-fence techniques. Modern cryptography distinguishes between symmetric and asymmetric ciphers. Symmetric (or secret-key) ciphers use the same key to encrypt and decrypt, while asymmetric (public-key) ciphers use a public key for encryption and a private key for decryption, enabling secure key exchange and digital signatures.

Examples and techniques. Symmetric algorithms designed for efficiency include block ciphers (for example AES) and stream ciphers (such as ChaCha20). Asymmetric algorithms include RSA and elliptic-curve cryptography (ECC). In practice, many systems combine these approaches, using public-key methods to exchange a symmetric key and then a fast symmetric cipher to protect the data. Modes of operation (such as CBC or CTR) determine how a cipher processes larger messages and helps preserve security properties.

Security and use. The strength of a cipher depends on the algorithm, the key length, proper implementation, and sound key management. Ciphers are employed across communications protocols, data storage, and authentication systems to ensure confidentiality, integrity, and, in some cases, non-repudiation.