Digital Signatures

Digital signatures use asymmetric cryptography to verify the authenticity and integrity of digital messages, documents, and software.

How Digital Signatures Work

A sender hashes the message and encrypts that hash with their private key to create a signature. The recipient decrypts the signature with the sender's public key and compares it to their own hash of the message to confirm it matches.

What They Guarantee

A valid digital signature confirms three things: the message came from the claimed sender (authentication), it wasn't altered in transit (integrity), and the sender cannot later deny sending it (non-repudiation).

Common Use Cases

Digital signatures secure software updates, verify email authenticity through protocols like DKIM, and validate SSL/TLS certificates that browsers rely on to confirm a website's identity.

Relevance to Security Testing

Understanding digital signatures helps security professionals evaluate whether software and communications in an organization are properly verified, reducing the risk of tampered updates or spoofed communications.