International Association
for Cryptologic Research

Ciphertext Policy Attribute Based Encryption (CP - ABE) is a public key primitive in which a user is only able to decrypt a ciphertext if the attributes associated with secret key and the access policy connected with ciphertext matches. CP-ABE provides both confidentiality and access control to the data stored in public cloud. Anonymous CP-ABE is an adaptation of ABE where in addition to data confidentiality and access control, receiver anonymity is also provided. Recently, Koo et al. (2013) proposed a scheme in the area of anonymous CP-ABE. We found security flaws in Koo et al.’s scheme. Their scheme does not support anonymity of the intended receiver, which was the main security claim in [8]. In this paper, we show how one can identify the receiver in Koo et al.’s scheme.