To enhance the security

many signature schemes were designed based on two hard problems

such as factoring and discrete logarithm. The major goal of these schemes is that they cannot he broken if both problems cannot be solved simultaneously. However

--. this paper shows that YL scheme can be broken if the factoring problem is solved

LC scheme is insecure against forgery if the discrete logarithm problem is solved. A new signature scheme is proposed that is really based on two hard problems simultaneously

which can also make the message recovered. Comparing with other schemes

this scheme is more efficient.