Energy big data: A survey <s> 3) ACCESS CONTROL SCHEME <s> As more sensitive data is shared and stored by third-party sites on the Internet, there will be a need to encrypt data stored at these sites. One drawback of encrypting data, is that it can be selectively shared only at a coarse-grained level (i.e., giving another party your private key). We develop a new cryptosystem for fine-grained sharing of encrypted data that we call Key-Policy Attribute-Based Encryption (KP-ABE). In our cryptosystem, ciphertexts are labeled with sets of attributes and private keys are associated with access structures that control which ciphertexts a user is able to decrypt. We demonstrate the applicability of our construction to sharing of audit-log information and broadcast encryption. Our construction supports delegation of private keys which subsumesHierarchical Identity-Based Encryption (HIBE). <s> BIB001 </s> Energy big data: A survey <s> 3) ACCESS CONTROL SCHEME <s> We propose a Multi-Authority Attribute-Based Encryption (ABE) system. In our system, any party can become an authority and there is no requirement for any global coordination other than the creation of an initial set of common reference parameters. A party can simply act as an ABE authority by creating a public key and issuing private keys to different users that reflect their attributes. A user can encrypt data in terms of any boolean formula over attributes issued from any chosen set of authorities. Finally, our system does not require any central authority. ::: ::: In constructing our system, our largest technical hurdle is to make it collusion resistant. Prior Attribute-Based Encryption systems achieved collusion resistance when the ABE system authority "tied" together different components (representing different attributes) of a user's private key by randomizing the key. However, in our system each component will come from a potentially different authority, where we assume no coordination between such authorities. We create new techniques to tie key components together and prevent collusion attacks between users with different global identifiers. ::: ::: We prove our system secure using the recent dual system encryption methodology where the security proof works by first converting the challenge ciphertext and private keys to a semi-functional form and then arguing security. We follow a recent variant of the dual system proof technique due to Lewko and Waters and build our system using bilinear groups of composite order. We prove security under similar static assumptions to the LW paper in the random oracle model. <s> BIB002
All the sensitive information must be sent separately to the specific terminals, thus access should be restricted and controlled. Sahai and Waters  proposed a cryptographic protocol called Attribute Based Encryption (ABE) which is mainly to distribute attributes to senders and receivers so that only the receiver with matching attributes set has the access to the data. However, this protocol is restricted to only support threshold access structures. Therefore, many researches have been launched to improve this protocol. Goyal et al. BIB001 proposed a novel ABE scheme called Key-Policy based (KP-ABE) scheme which can handle any monotonic access structure. Bethencourt et al.  proposed another type of protocol which is known as Ciphertext-Policy ABE (CP-ABE). In these schemes, ciphertexts are encrypted under a given access structure with a set of attributes. Only a receiver has a matching attributes set can it decrypt the information. Lewko and Waters BIB002 proposed an access control scheme and gave limited access to authorized data users. It is mainly based on a ABE cryptographic technique where RTUs have attributes and cryptographic keys distributed by multiple Key Distribution Centers (KDCs). When an RTU R i wants to store a message m, R i defines an access structure S firstly which helps it to select the authorized users to access the message m. R i then creates a k × l-matrix R (k represents the attributes' number in the access structure and l is the leaves' number in the access spanning tree). R i also defines a mapping function ψ of which rows is a set of attributes: ψ : {1, 2, · · · , k} → W, where W means a attributes set. Obviously, ψ is a permutation. Then the RTU R i runs the ABE encryption algorithm to calculate the ciphertext C by C = ABE.Encrypt(m, R, ψ). Ciphertext C is thus stored in the data repository. If a user u has a valid set of attributes, his request to access to the ciphertext C from the data repository will be accepted and the C will be decrypted into the message where SK [i, u] represents the secret key of KDC corresponding to the attribute i given to the user u.