A Digital Signature is a cryptographic mechanism that provides authentication, integrity, and non-repudiation for digital documents and messages. The signer uses their private key to sign a hash of the document. Anyone can verify the signature using the signer’s public key, confirming both the signer’s identity and that the document hasn’t been modified.
Digital signatures differ from electronic signatures (which might just be a typed name). They provide mathematical proof of authenticity that holds up legally and technically. Common algorithms include RSA signatures, DSA, and ECDSA.
CISSP Relevance
Domain 3 (Security Architecture and Engineering) covers digital signatures as a key cryptographic application. Understand how signing works (hash then encrypt with private key), how verification works (decrypt with public key, compare hashes), and what properties signatures provide. Know the difference between digital and electronic signatures.
Signature standards are defined in FIPS 186-5 Digital Signature Standard.
Related terms: Hash Function, PKI