Cryptanalysis of Attribute-based Ring Signcryption Scheme

Signcryption can offer authentication and confidentiality simultaneously with better efficiency than traditional signature-then-encryption approach. Ring signature enables a user to conscribe arbitrarily a group of ring members and sign a message on behalf of the ring (which includes himself) without revealing his real identity. By integrating the notion of signcryption and ring signature, ring signcryption has been initialized to leak secrets in an authenticated and confidential way anonymously. Recently, Guo et al. (Guo Z, Li M, Fan X. Attribute-based ring signcryption scheme. Security and Communication Networks, vol. 6, no. 6, pp. 790-796, 2013) proposed a ring signcryption scheme in attribute-based cryptography. Furthermore, they claimed that their scheme can satisfy confidentiality and unforgeability in the random oracle model. Unfortunately, by giving concrete attacks, we indicate that Guo et al.’s attribute-based ring signcryption scheme doesn’t provide confidentiality and unforgeability.