What is Full Domain Hash (FDH) Signature?

A full domain hash (FDH) signature is a cryptographic signature mechanism that makes use of the hash-and-sign paradigm. FDH signatures leverage Rivest–Shamir–Adleman (RSA) public-key cryptography (PKC) and are provably secure using the random oracle model. FDH signatures are part of a group of standardized signatures that are widely used in PKC.