属性基加密及其应用研究详解.ppt

为什么进行检索 基本框架 具有关键字检索的ABE 具有关键字检索的外包ABE Our Proposed Schemes Idea 报告内容 背景及相关工作 一 存在问题 二 具有固定密文长度ABE 三 具有关键字检索的ABE 四 具有用户撤销的ABE 五 属性基加密的应用 六 Attribute Revocation Ciphertext User B (History, Male, Teacher) User A (History, Male, Teacher) User B (History, Male, Teacher) User A (History, Male) (History AND Teacher) When a user’s attribute is changed, his access to a ciphertext also will be changed. √ √ × √ Attribute is revoked. Private key will be updated. Before Revocation After Revocation User Revocation When a user leaves from a company to another one, his access to the ciphertexts also will be changed. User A User B User B User C Company UP Company TH √ × √ √ A simple method Tysowski et al. gave an easy method to perform user revocation operation through combining the techniques of CP-ABE with re-encryption. In their scheme, each user belongs to a group and holds a group secret key issued by the group. However, their scheme is not secure against collusion attack performed by revoked users through cooperating with existing users. P.K. Tysowski and M.A. Hasan: Hybrid Attribute-Based Encryption and Re-Encryption for Scalable Mobile Applications in Clouds. In: IEEE Trans, Cloud Computing’13, pp. 172-186. 2013. Ciphertext is associated with an access structure and a group public key. CP-ABE of Tysowski et al. Secret key is labeled by a set of attributes and a group secret key. AND OR History 2012 2013 {History, 2012, Student} Bob Ciphertext GPK GMK {History, 2012, Student} Bob AND OR History 2012 2013 Satisfy Bob Successfully decrypt History AND (2012 OR 2013) GPK Ciphertext CP-ABE of Tysowski et al. GMK Satisfy GPK Ciphertext (History AND Teacher) ∪ GPK User A {History, Teacher} GMK User B {History, Student} GMK User B {History, Student} Updated GMK User A {History, Teacher} GMK Group Hohai Group Hohai Ciphertext (History AND Teacher) ∪ Updated GPK Re-encryption √ × × × Leave User B {History, Student} Updated GMK User A {History, Teacher} GMK Group Hohai {History,