Designated Confirmer Signatures and Public-Key Encryption are Equivalent

Abstract

The concept of designated confirmer signatures was introduced by Chaum [Cha94] to improve a shortcoming of undeniable signatures. The present paper formalizes the definition of designated confirmer signatures and proves that a designated confirmer signature scheme is equivalent to a public-key encryption scheme with respect to existence. In addition, the paper proposes practical designated confirmer signature schemes which are more efficient in signing than the previous scheme [Cha94].