A proxy signature scheme enables a proxy signer to sign messages on behalf of the original signer. A blind signature is the concept with a salient feature that the signer cannot make a linkage between the blind signature and the identity of the requester. Most of the existing digital signature schemes were developed based on a single hard problem like factoring, discrete logarithm or elliptic curve discrete logarithm problems. In this paper, we proposed an improved proxy blind signature scheme based on multiple hard problems namely factoring and elliptic curve discrete logarithm problems (ECDLP), which satisfies the security properties of both the blind signature scheme and the proxy signature scheme. We combined the two problems into the delegating stage. Our scheme provides longer and higher security level than that scheme based on one problem. Index Terms—Blind signature, Elliptic curve discrete logarithm problem (ECDLP), Factoring, proxy signature