Research On Database Encryption System

With the development and wildly used of computer technology, people depend on it in their everyday life. But the accidents that stealing or altering important data information happened frequently, people have to put more emphasis on information security.As the "warehouse" of data, the security of database takes a very important role in computer security. To encrypt data in database is one of the important ways to protect database information security, so, it has crucial meaning to have some research of encryption technology in database.In the field of database encryption, there have two central problems unsolved: one is management of encryption key; since storage of data in database is concentrated and there have some logical relationship among these data, it needs a secure, practicable method of cipher key management. The other problem is caused by the order shift of plaintext after encryption, so, it needs a method which can query cipher text quickly.In this thesis, we propose a two-step key management system to solve the first problem. The first key is primary key, client keeps one part of it and special database server keeps the other part, it can be dynamically assembled by authentic third party process when using; the second key is working key preserved after being encrypted by primary key, it used to encrypt relevant data. In this way we can achieve the security of key management, also keeps its usability.Since the query sentence is plaintext, we should decrypt cipher text first and compare it with query sentence. It is not reasonable to decrypt all relevant cipher text, so, a secure and quick method of cipher text query is needed. In this thesis, we use Cipher Field Index Table to achieve querying cipher text by querying index table instead. This structure can make sure that database can not be decrypted easily without key even being stolen and legal user can quickly query cipher text.