基于格和分层身份结构的广播加密方案

提出基于格和分层身份结构的广播加密方案。该方案采用格表示用户身份信息，通过格和子格的结构关系表示分层结构，以格的短基表示用户的私钥，利用格基生成算法迭代生成每层格的短基，基于格中错误学习难题设计加、解密算法。理论分析证明，对于非授权用户，该方案在适应性选择密文攻击下具有不可区分安全性，对于授权用户，在选择密文攻击下具有前向安全性，与基于双线性对的广播加密方案相比计算速度更快。

Broadcast Encryption Scheme Based on Lattice and Hierarchical Identity Structure

This paper presents a broadcast encryption scheme based on lattice and hierarchical identity,whose encryption and decryption algorithms are based on Learning with Error(LWE) hard problem.Each user’s identity is associated with a lattice matrix,and the relationship between the lattice and its sub-lattice can easily represent the hierarchical identity construction.Short basis of a lattice is treated as a private key of a user,and based on the lattice delegation algorithm,the private key for each level’s user can be derived.Theory analysis proves that the scheme is Indistinguishable-Chosen Ciphertext Attack 2(IND-CCA2) secure against the attacks by outsider users and Forward Safe-Chosen Ciphertext Attack(FS-CCA) secure against the attacks by authorized receivers.Compared with the broadcast encryption scheme based on the bilinear mapping,it is more efficient in the encryption and decryption.