Comment on Anonymous Multi-receiver Identity-Based Encryption Scheme

Anonymous receiver encryption is an important cryptographic primitive. It can protect the privacy of the receiver. In 2010, Fan et al proposed an anonymous multi-receiver ID-based encryption by using Lagrange interpolating polynomial. However, Wang et al showed that Fan et al´s scheme didn´t satisfy the anonymity of the receivers. Then they provided an improved scheme to fix it and showed that the improved scheme was secure. Unfortunately, in this paper, we pointed out that Wang et al´s improved scheme did not satisfy the receiver´s anonymity by analyzing the security of the scheme yet. After analyzing the reason to produce such flaws, we gave an improved method to repair it and showed that our improved scheme could satisfy the receiver´s anonymity. And the improved scheme has the advantage over Wang et al´s scheme in terms of computational cost.