What is a digital signature?

A digital signature verifies that a message truly came from the claimed sender and was not altered in transit.

In email, this is managed through DKIM, which signs parts of the message with a private key. The receiver checks the signature using the sender’s public key stored in DNS.

It is the wax seal on the captain’s orders, proving authenticity. The DKIM signature provides both authenticity and integrity, confirming who sent it and that the protected parts of the message were not modified.