Cryptography
Private Key
Also known as: Secret key (asymmetric)
Definition
The secret half of an asymmetric key pair, used to decrypt ciphertext addressed to its owner or to create digital signatures that prove the owner's identity.
Examples
- An SSH private key file (e.g., id_ed25519) used to authenticate to remote servers.
- A web server's TLS private key paired with its X.509 certificate.
Related terms
Public Key
The freely distributable half of an asymmetric key pair, used to encrypt messages for its owner or to verify digital signatures produced by the matching private key.
Public-Key Cryptography
A branch of cryptography that uses paired public and private keys to enable encryption, key exchange, digital signatures, and authentication without a pre-shared secret.
Asymmetric Encryption
A cryptographic scheme that uses mathematically linked key pairs — a public key for encryption and a private key for decryption — to enable secure communication without prior secret sharing.
Digital Signature
A public-key cryptographic mechanism that proves the authenticity, integrity and non-repudiation of a message or document.
Key Rotation
The periodic replacement of cryptographic keys with new ones to limit the volume of data protected by any single key and contain the impact of compromise.
Perfect Forward Secrecy
A protocol property ensuring that the compromise of long-term keys does not allow decryption of past session traffic.