Efficient Privacy-Preserving Ciphertext-Policy Attribute Based Encryption and Broadcast Encryption

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Ciphertext Policy Attribute Based Encryption (CP-ABE) enforces expressive data access policies and each policy consists of a number of attributes. Most existing CP-ABE schemes in occur very large ciphertext size, which increases linearly with respect to the number of attributes in the access policy. Recently, Herranz et al. proposed a construction of CP-ABE with constant ciphertext. However, does not consider the recipients' anonymity and the access policies are exposed to potential malicious attackers. On the other hand, existing privacy preserving schemes protect the anonymity but requires bulky, linearly increasing ciphertext size.