A digital signature is a cryptographic mechanism that provides authentication, integrity, and non repudiation for a message or document. The signer hashes the content and encrypts that hash with their private key. Anyone holding the matching public key can verify the result, confirming both who signed it and that not a single byte has changed since. That combination is what gives a signature its legal and technical weight.
It helps to separate a digital signature from a plain electronic signature, which might be nothing more than a typed name pasted into a document. A digital signature offers mathematical proof of origin, whereas an electronic signature often proves very little on its own. Common algorithms include RSA, DSA, and the elliptic curve variant ECDSA. One point candidates miss is that because signing uses the sender’s private key, only that person could have produced the signature, and that is precisely what delivers non repudiation.
Why do digital signatures matter for the CISSP exam?
Signatures fall under Domain 3: Security Architecture and Engineering, worth 13 percent of the exam. Be ready to walk through signing and verification step by step and to explain the three properties a signature provides.