The former fault analysis on RSA with "Left-to-Right" was based on modifying the public modulus N, but it is
difficult to be taken in practice. In order to find a more practical attack method, considering the characteristic that the
multiplier of microprocessor is easy to affect by voltage, the fault can be injected into the multiplier during the RSA
signature by adjusting the voltage. This paper proposes a new fault analysis on RSA signature based the error with
multiplier, improving the feasibility of attack, and extends the attack to RSA with fixed-window algorithm. In the end,
the complexity of algorithm is analyzed; the expansibility and feasibility of algorithm are proved by demonstrating in
theory and simulation experiments. The results of experiment show that the new fault analysis algorithm is more
practical in operation.