Which service supports proving to a third party who signed a message?

1. A signature can be checked by anyone holding the public key. 2. That lets a dispute be settled by an outside party. 3. Non-repudiation is a service using a digital signature to determine whether a message was signed by a given entity. 4. So the answer is non repudiation. _Source: NIST SP 800-175B Rev. 1, 'Guideline for Using Cryptographic Standards in the Federal Government'_