| Since the globe walked into the information age, network security has been playing an increasingly important role in our life, work and study. Large amounts of information like personal information, corporate data and national confidential paper is stored after encryption. The frequent happening of network attacks contributes to the development of encryption algorithms, in which hash algorithms are widely used due to the difficulty of reserving decryption directly. Additionally, the most popular method to encrypt hash algorithms today is pre-calculating the Rainbow Table. Since there are millions or even billions of kinds of possibilities of plaintext to considerate, we need to build TB or even PB Rainbow Table to hold those countless plaintext, which also means great demand for large amounts of data.In this paper, the writer designed and implemented a cipher-text decrypting system aimed at several popular hash algorithms like MD5, SHA-1, which is based on pre-calculating Rainbow Table and is able to decrypt up to 7 decimals cipher-texts. What’s more, to meet the TB-level data requirements, the system improved the pre-calculating Rainbow Table method by adding index to the rainbow chain and storing the start point and end point of rainbow chain separately, which not only decrease the checking time but also enhance the decrypting efficiency. Besides, there are some basic functions in the system, for example logging in, registering, managing personal information, checking history and give feedbacks, at the same time, there are also administers in the system, who can also log in the system with authentication to manage users and deal with users’ feedbacks.The system is modeled by UML modeling language. The system uses C# and Javascript language to program, and VS2008 and Server SQL 2005 are used to build the underlying framework. Finally, using the black box testing method, the system is tested. |
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