SecretKey

A secret key, in cryptography, is a piece of information used by symmetric algorithms to perform operations such as encryption, decryption, or message authentication. The key must be kept confidential by the communicating parties to maintain the security of the system. When a secret key is compromised, the confidentiality and integrity of the protected data are at risk.

In symmetric cryptography, the same secret key is used for both encryption and decryption. Algorithms such as AES, ChaCha20-Poly1305, and DES rely on secret keys of varying lengths to provide confidentiality. Secret keys are also used in message authentication codes (MACs), such as HMAC, to verify that a message has not been altered and originates from a trusted source. The term secret key is often used interchangeably with symmetric key, though in public-key cryptography a private key is also kept secret but serves a different role.

Key management is a central concern: keys should be generated with sufficient entropy, stored securely (for example, in hardware security modules or key vaults), and rotated or revoked as needed. Secure key exchange mechanisms, such as using public-key cryptography or Diffie-Hellman, are used to establish secret keys between parties without exposing them to eavesdroppers. Proper handling, storage, and destruction of secret keys are essential to prevent leakage and maintain long-term security.

In common applications, secret keys enable data-at-rest encryption (disk or database encryption) and data-in-transit encryption (TLS session keys), while ensuring that only authorized parties can decrypt or verify protected information.