Digital Signature

What is Digital Signature?

A digital signature is a specific type of electronic signature that uses cryptographic algorithms to create a mathematically verifiable link between a signer and a document. Unlike simpler forms of electronic signatures, digital signatures rely on public key infrastructure (PKI) to provide strong guarantees about authenticity and integrity.

The process works as follows: when a signer applies a digital signature, the signing software generates a unique hash of the document content. This hash is then encrypted using the signer's private key, creating the digital signature. Anyone can verify the signature using the signer's public key — if the decrypted hash matches a freshly computed hash of the document, the signature is valid and the document is unaltered.

Digital signatures are considered more secure than simple electronic signatures because they provide non-repudiation (the signer cannot credibly deny having signed), integrity verification (any change to the document invalidates the signature), and authentication (the signature is tied to the signer's identity through their digital certificate).

Under the eIDAS Regulation, advanced and qualified electronic signatures must use digital signature technology. Certificate authorities issue the digital certificates that underpin this process, acting as trusted third parties that verify signer identities.