# Digital Signature

A cryptographic technique that verifies the authenticity and integrity of a digital message, document, or software file.

A **digital signature[↗](/digital-signature)** is a cryptographic technique, built on public-key cryptography[↗](/public-key-cryptography), that lets a recipient verify both who sent a digital message or file and that it hasn't been altered since it was signed. The sender uses their private key to generate the signature, and anyone with the corresponding public key can verify it.

Digital signatures are used to sign software updates so your computer can confirm they really came from the vendor, to sign legal documents, and to secure email. If even a single character in a signed document changes after signing, the signature verification fails, immediately revealing the tampering.