A New Signature Scheme Based on Factoring and Discrete Logarithm Problems

It is well-known that Diffie and Hellman gave the concept of public key cryptography. Since then, several public key cryptosystems based on a hard mathematical problem either factoring or discrete logarithms have been proposed. Those cryptosystems in which said problem was easy to solve were found to be insecure. Also, the encryption in digital signature scheme is based on the same mathematical problems which are used to design public key cryptosystems. Hence, security of the digital signatures depends upon the hardness of either factoring or discrete logarithm. However, most of these are found to be insecure. In a paper, Harn and He-Kiesler proposed digital signatures which were based on factoring and discrete logarithm problem both.