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In a cloud, the data are subjected to many forms of security and privacy issues. A fundamental task in security is to create cryptographic primitives based on hard mathematical problems that are computationally intractable. Here, the paper propose a Multi authority based privacy-preserving CP-ABE with captcha protocol (MAPA-c) to address security and privacy issue for cloud storage. In the MAPA-c 1) CaRP are both a captcha and a graphical password scheme, which addresses a number of security problems altogether, such as online guessing attacks, relay attacks. 2)Multi access authority is achieved by MA-CP-ABE scheme which provides anonymous access request matching mechanism with security and privacy considerations; and 3) attribute based access control is adopted to realize that the user can only access its own data fields. |
