Research And Implementation Of Two Common Compressed File’s Password Recovery

Compressed file need less storage and transport bandwidth. So, it becomes more and more popular today. However, when we face an encrypted compressed file without password, how to recover the file becomes a hot topic.This paper focuses on password recovery algorithms and algorithms optimization about two popular compressed modes named ZIP and RAR. The article will divides password recovery into three steps: 1) Analyze the structure of the compressed file and their encryptionrelated key fields, then develop extraction program to extract ciphertext; 2) Due to the special nature of the compressed file’s encryption and GPU’s architecture, this paper develop the preliminary program which is run on GPU to filter passwords in some conditions; 3) To develop the program which is run on CPU to check the passwords gained by preliminary program and gain the correct password. Here the password recovery program is divided into three parts, not only make the program operational efficiency, and effectively solve the problem that if the file recovered by others it may discloses the file’s information.To further enhance the speed of password recovery, this paper optimize the codes base on the compressed file’s structure, the basic algorithms, the system we used for password recovery and architecture of GPU’s framework to achieve maximum efficiency.Finally, the codes’ correctness and efficiency can be proved by test results. The paper proves the optimization techniques by comparing test result before and after.