What is a Digital Signature?

A digital signature is a virtual fingerprint used to identify users, validate their consent and protect data in digital communications. Examples include tokens, biometric data, passwords, and digitized handwritten signatures. They are used in emails, credit card transactions, or legal documents.

Digital signatures ensure privacy, authentication, integrity, and non-repudiation.

An Advanced Electronic Signature (AES) and Qualified Electronic Signature (QES) have asymmetric cryptography technology and public key infrastructure containing a digital certificate and the highest security level. For example, a sender uses a hash algorithm to create a hash of data. He then feeds his private key and the hash data into a signature algorithm to create the digital signature. This signature is attached to the hashed data and sent to the receiver.

The receiver feeds the digital certificate and the public key into a verification algorithm to create an output. The receiver also runs the same hash function on the received data to create a hash value.

For verification, the output received by the verification algorithm and the hash value should match for the receiver to confirm the validity of the digital signature.

Since the sender creates a digital signature using a private key that no one can access, he cannot repudiate signing the data in the future.