Delegation of signing is a working way common in oce automation work, and is
also an important approach to establish trust. Proxy signature is an important
cryptographic primitive for delegating the signing powers and it has found many
real world applications. The existing proxy signature schemes from factorization
assumption are either insecure or inecient. In this paper, we propose a novel,
ecient and provably secure proxy signature scheme from factorization. Our
construction makes use of a factorization based key-exposure free chameleon hash
function in the delegation phase and the proxy signer needs only to nd a collision
to a chameleon hash value to generate a valid proxy signature. As a result, our
scheme is highly ecient in terms of the computation of a proxy signature. We also
provide a formal security proof by classifying the adversaries into three categories.
Comparisons demonstrate that the new scheme outperforms the known ones in
terms of security, computational eciency and the length of the public key.