Digital signature scheme (DSS) can be divided into two categories; ordinary signature (OSS) and function-based signature (FBS). OSS enables a legal signer to sign an electronic message digitally and allows the owner of the message or signature verifier to check the validity of the resultant signature whereas FBS provides the ordinary signature with some added or extra properties and supports many applications in electronic-based business such as e-cash or payments systems, electronic voting and contract signing. In this book, we study cryptographic algorithms or protocols of both OSS and FBS...