Protecting User Privacy By Using Decentralized Key-Policy Attribute-Based Encryption

can issue the secret key to user independently without any co-operation of a central authority. It means that that there is no need to trust on to the central authority due to this even if multiple authorities are corrupted they can’t collect the users attributes by tracing users GID. In decentralized key-attribute based encryption both the user secret key and the ciphertext are label with set of different attribute. Message can be encrypt under set of attribute so if anyone want the decrypt the ciphertext the receiver must obtain data only when there is match between his secret key and attribute listed in the ciphertext. In multi authority ABE secret key of different users from different authorities must be tied to his global identifier (GID). To avoid collagen attack this is not efficient to protect the users privacy. So we propose Decentralized key policy ABE scheme to protect the users privacy in this scheme each authority can issue secrete key to users separately without having any idea of his GID. This scheme required standard complexity assumption e.g. (Decisional by linear deffie-Hellman) dbdh instead of non standard complexity assumption (e.g., q-decisional Diffie-Hellman inversion) which is used in previous scheme. Keywords- Attribute based encryption multi authority, privacy. I