From CryptoDox, The Online Encyclopedia on Cryptography and Information Security
Here signatures can only be verified with the signer's consent. However, if a signature is only verifiable with the aid of a signer, a dishonest signer may refuse to authenticate a genuine document. Undeniable signatures solve this problem by adding a new component called the disavowal protocol in addition to the normal components of signature and verification. This is implemented using Public-key Cryptography based on the discrete logarithm problem.