For improving proxy-signature research, Sun attempted to resolve problems related to defective security in the scheme of Yi. However, both Yi and Sun's schemes involve a significant number of exponential operations to verify the proxy signature. Accordingly, an improvement is proposed here to change the exponential operations into elliptic curve multiplicative ones. As proposed by both Koblitz and Miller in 1985, the elliptic curve is used in developing the cryptosystems. The elliptic curve cryptosystem can achieve a level of security equal to that of RSA or DSA but has a lower computational overhead and a smaller key size than both of these. Therefore, it is used in Sun's schemes to improve their efficiency.
