AbstractAs a kind of special digital signature, proxy re‐signature is becoming more and more important in transparent certification and management of group signatures. But most existing proxy re‐signature schemes cannot resist collusion attack. So we construct a scheme by using dual modulus technology and lattice structure. Dual modulus technology can ensure that our solution can resist various collusion attacks. Lattice structure can ensure that our scheme is secure in the postquantum era. Compared with the previous scheme, our scheme is unidirectional and certificateless, is secure in the post‐quantum era, does not require key escrow, can prevent man‐in‐the‐middle attacks, and can resist collusion attacks of proxy and delegatee as well as proxy and delegator. Moreover, our scheme is unidirectional and has better privacy. Furthermore, under the random oracle model, we prove that our scheme is strong nonforgeability against external attackers and the internal key generation center.