Identity-based blind proxy re-signature (IDBPRS) not only has the functionality of signature conversion, but also can protect the privacy of the signed data. In this paper, we present an efficient IDBPRS scheme in the standard model. The proposed scheme is blind and bidirectional, and is proven to be existentially unforgeable under the Diffie-Hellman assumption. Furthermore, the performance analysis results show that our IDBPRS scheme outperforms the Wang's IDBPRS scheme in terms of signature length and computational cost.