Digital Signatures Explained

Digital signatures are the backbone of modern document security. Unlike a handwritten signature that can be copied, a digital signature is mathematically bound to both the signer's identity and the document's content.

Public Key Cryptography

At the heart of digital signatures lies public key cryptography. Each signer has a key pair: a private key (kept secret) and a public key (shared openly). The private key creates the signature, and anyone with the public key can verify it — without ever needing access to the private key itself.

The Signing Process

When you sign a document, the system first computes a hash — a fixed-size fingerprint of the document's contents. This hash is then encrypted with your private key to produce the signature. The result is a compact proof that you endorsed that exact version of the document.

Verification

To verify, the recipient decrypts the signature using the signer's public key, recomputes the document hash, and compares the two. If they match, the document is authentic and unaltered. If not, something has changed.

Beyond Integrity

Digital signatures provide three guarantees: integrity (the document hasn't been modified), authentication (it came from the claimed signer), and non-repudiation (the signer cannot deny having signed it).