A Survey On Improving Privacy And Security In Decentralized Cipher Text-Policy Attribute-Based Encryption
In traditional encryption scheme, user encrypts the data by using a single key which is associated with the user.
Cipher Policy Attribute Based Encryption is another encryption technique in which central authority distributes key to the
user by using which the data is decrypted under a logical formula. In order to reduce the trust on central authority Privacy
Preserving Multi authority Attribute Based Encryption (PPMA-ABE) scheme is introduced. In this scheme, central authority
is used only for system initialization. These multiple authorities coordinate with each other and generate the secret keys for
the user by knowing his/her attributes. Multiple authorities can identify a user by collecting and analyzing users attribute.
Hence the PPMA-ABE scheme is not suitable for protecting the user’s privacy. Moreover, there is another efficient public
key encryption technique called Cipher Policy ABE (CP-ABE) in which the messages are encrypted by using flexible access
structure which is selected by encrypt generator. These techniques are based upon the central authority . Since the trusted
authority is a central system which may get crashed or hanged when the overload increases. Therefore it is a challenging task
to construct a PPMA-ABE scheme which doesn’t use a central authority and the attributes will be hidden from the
authorities. These ideas are extended into a technique called Privacy –Preserving Decentralized CP-ABE (PPDCP-ABE). In
this paper the trust on the central authority is reduced and user’s identity is protected. In this scheme, each and every
authority works independently based upon their rules. Furthermore, multiple authorities generate the secret keys for user
without knowing the user’s attribute.