Multi Authority Attribute Based Encryption

Attribute based encryption (ABE) is an important branch of identity basedencryption. In this system,a series of description attributes instead of the identity, and amore flexible access structure is added to this system. There are two kinds of attributebased encryption：key-policy based and ciphertext-policy based. If and only if attributesmatch access structure, we can get decryption. The most advantage of the system is thatsender does not need to know the specific receiver, and receiver who is consistent withthe corresponding conditions can decrypt the message from the sender. Attribute basedencryption can be widely adopted in many application scenarios such as distributedcomputing and network storage.But the existing attribute-based encryption (ABE) is too weak to get application inthe actual environment. One of the reasons is the management problems of attributeauthorities. Lin presented a threshold multi authority attribute basedencryption(MA—ABE)scheme without a central authority. It removed the centralauthority which has the decryption ability and meets the requirements of a distributedenvironment. And it made all the authority have the coequal status. He used a secretsharing system in attribute-based encryption, so that it improved usability. On the basisof his scheme, we use another secret sharing system, so that we can add or removeattribute authority flexibility. Another reason is that the existing ABE can’t resistcollusion attack. Lin’s scheme resists collusion attack through limiting the number ofusers. In our scheme, we add a hash function to hide users’ GID, so that it can preventcollusion attack between users, to guarantee the security of encryption scheme.