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Cipher Algorithm

A mathematical procedure for encrypting and decrypting data to protect confidentiality.

CryptographyAlso called: "encryption algorithm", "cryptographic cipher"

Ciphers transform plaintext into ciphertext using keys to prevent unauthorized access.

Types of ciphers

  • Symmetric: Same key for encryption/decryption (AES, DES, 3DES).
  • Asymmetric: Public key encrypts, private key decrypts (RSA, ECC).
  • Stream: Encrypt data bit-by-bit or byte-by-byte (RC4, ChaCha20).
  • Block: Encrypt fixed-size blocks (AES, Blowfish).

Modern algorithms

  • AES-256: Current standard for symmetric encryption.
  • RSA-2048/4096: Widely used for asymmetric encryption.
  • ChaCha20-Poly1305: Fast stream cipher with authentication.
  • ECC: Efficient public-key cryptography.

Deprecated/insecure

  • DES: 56-bit key, crackable.
  • MD5, SHA-1: Collision attacks possible.
  • RC4: Biases in output stream.
  • ROT13, XOR (simple): Not cryptographically secure.

Key concepts

  • Key length: Longer keys = stronger encryption.
  • Mode of operation: CBC, GCM, CTR (for block ciphers).
  • Initialization vector (IV): Randomizes encryption.