Undeniable signatures are a form of digital signature invented by David Chaum and Hans van Antwerpen in 1989. They have two distinctive features,

1. The verification process is interactive, so the signer can limit who can verify their signature.
2. 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.

See also

• Topics in cryptography

References

• David Chaum, Hans van Antwerpen: Undeniable Signatures; Crypto'89, LNCS 435, SpringerVerlag, Berlin 1990, 212-216.

Cryptography