Abstract: This paper presents a key management scheme based on elliptic curve cryptosystem to solve the problem of rights management among hierarchical users and access the encrypted database. In the proposed scheme, each user can independently choose own user key, and securely transfer it to trusted center. The trusted center calculates the  relational parameters of the user having the partially ordered relation by using the elliptic curve cryptosystem after collecting the secret key parameters. The higher-privileged class will have the right to derive the key information created or owned by a user in a lower-privileged class, and then take advantage of it to decrypt the encrypted database which is also created by the lower-privileged class. The update method of the encrypted database is also considered after the partially ordered relation is changed. Experiments show that key generation, key derivation and access database have high efficiency and security.

Key words: encrypted database, key management, elliptic curve cryptosystem, partially ordered relation, user hierarchy

摘要： 针对等级体制下用户权限管理和访问密文数据库的问题，提出了基于椭圆曲线密码体制的密钥管理方案。该方案中每个用户都可以独立选择自己的用户密钥，并安全传送给可信中心，可信中心在收集完密钥参数之后使用椭圆曲线密码体制计算出具有偏序关系的用户关系参数。高级别用户利用关系参数和用户密钥便可以安全有效地推导出低级别用户的密钥信息，然后利用密钥信息解密低级别用户的密文数据库。方案中还考虑了偏序关系变化后密文数据库的更新方法。实验表明，安全等级的密钥推导和访问数据库具有较高的效率和安全性。

关键词: 密文数据库, 密钥管理, 椭圆曲线密码体制, 偏序关系, 用户分级