A delegateable signature scheme is a signature scheme where the owner of the signing key(Alice) can securely delegate to another party(Bob) the ability to sign on Alice's behalf on a restricted subset S of the message space. Barak first defined and constructed this signature scheme using non-interactive zero-knowledge proof of knowledge(NIZKPK)[1]. In his delegateable signature scheme, the function of NIZKPK is to prevent the signing verifier from tell which witness(i.e. restricted subset) is being used
