CyberGlossary

Cryptography

Digital Signature

Also known as: Cryptographic signature, Public-key signature

Definition

A public-key cryptographic mechanism that proves the authenticity, integrity and non-repudiation of a message or document.

A digital signature is produced by hashing a message and encrypting that hash with the signer's private key; anyone with the corresponding public key can verify the signature, providing authentication, integrity, and non-repudiation. Common algorithms include RSA-PSS, RSA-PKCS#1 v1.5, ECDSA (over P-256/P-384), EdDSA (Ed25519, Ed448) and the NIST post-quantum signature ML-DSA (CRYSTALS-Dilithium). Digital signatures underpin TLS certificates, code signing, software updates, blockchain transactions, and email standards like S/MIME and DKIM. Their security relies on the hardness of factoring or discrete-logarithm problems and on collision-resistant hash functions; quantum computers would break classical schemes, motivating the ongoing migration to ML-DSA and SLH-DSA.

Examples

  • TLS server certificates are issued and validated using ECDSA or RSA signatures.
  • Apple notarisation signs macOS binaries to assure users they come from a known developer.

Related terms