Study On Attribute-based Cryptographic Algorithms

Since 2006 Google CEO Eric Schmidt puts forward the concept of "cloud computing" in the search engine assembly for the first time, cloud computing has been a hot area of the next generation Internet applications technology. In the cloud, what the researchers concern is how to achieve the data security through nontraditional access control policy. In addition, how to enjoy the convenience and fast of the cloud computing by the users are also concerned. In order to protect encrypted data security and achieve fine-grained access to data, attribute based encryption technique is proposed. Attribute-based encryption(ABE) is issued from identity-based encryption(IBE) technology. In the ABE, the decryption can be made without knowing the identity information of the encryptor, and it only needs to satisfy the corresponding access control policy. This thesis takes aim at the ABE and the contributions are specified as follows.1. The paper studies the existing IBE and proposes a new identity-based encryption scheme in the standard model. As its application, an efficient identity-based broadcast encryption(ABBE) is introduced. The new ABBE scheme achieves constant size ciphertexts and private keys, which not only gives the good trade-off between ciphertexts size and private keys size, but also provides a good trade-off between security and efficiency. Compared with the current identity-based broadcast encryption, the security of the scheme is reduced to a general assumption--DBDH assumption.2. Based on an ABBE, two efficient key-policy ABE schemes are proposed. The first scheme achieves sub-linear size ciphertext, and the second one contains only 3 elements. Both schemes have constant size private keys. In the random oracle model, both schemes achieve chosen plaintext security under the GBDH assumption. Based on both schemes, a chosen ciphertext attack security(CCA) scheme is also proposed.