Undeniable signature
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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 the signer can limit who can verify their signature.
- A disavowal protocol, that is a cryptographic protocol which will allow them to prove that a given signature is a forgery.
The first means that a signer can allow only those 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.
However because of this property it means that the signer may deny a signature which was valid. To prevent this we have the second property, a method to prove that a given signature is a forgery.
Further reading
- David Chaum, Hans van Antwerpen: Undeniable Signatures; Crypto'89, LNCS 435, SpringerVerlag, Berlin 1990, 212-216.
See also: Topics in cryptography