Undeniable signatures are a form of digital signature invented by David Chaum and Hans van Antwerpen in 1989. They have two distinctive features,
- The verification process is interactive, so that the signatory can limit who can verify the signature.
- A disavowal protocol, which is a cryptographic protocol that allows them to determine whether a given signature is a forgery.
The first means that a signatory can allow only others who are authorized to access the document to verify their signature. If the document were to be leaked to a third party, the third party would be unable to verify that the signature is genuine. This is a designated verifier signature.
However, because of this property it means that the signatory may deny a signature which was valid. To prevent this, there is the second property, a method to prove that a given signature is a forgery.
Famous quotes containing the words undeniable and/or signature:
“Only in men’s imagination does every truth find an effective and undeniable existence. Imagination, not invention, is the supreme master of art as of life.”
—Joseph Conrad (1857–1924)
“The childless experts on child raising also bring tears of laughter to my eyes when they say, “I love children because they’re so honest.” There is not an agent in the CIA or the KGB who knows how to conceal the theft of food, how to fake being asleep, or how to forge a parent’s signature like a child.”
—Bill Cosby (20th century)