基于字母频率的单表替换密码破译算法

Password Breaking Algorithm of Single Table Replacement Based on Frequency of Letters

替换式加密根据加密构成方式可分为移位、仿射、随机三类。论文对替换式加密的密文进行破译求解,主要依靠字母频率分布。对于移位采用对比统计字母的各移位数,在此基础之上确定移位数众数从而作为最终移位数。对于仿射、随机而言,不能简单获得所有位置的各个位移数。故而只有在此基础上,依据大数据样本高稳定性的特点,确定文中出现概率居前两位的字符与统计中前两位字符对应。在此基础上,采用欧几里得辗转除余法求解仿射。随机加密则采用数据字典进行查找分析。最后得到解密明文。最后的求解结果是,对于移位、仿射由于加密较为简单且变化有规律所以求解准确率较高,而随机需要对比计算,故而速度以及准确率有较大的不确定性,同时需求时间较长。

Replace cryptographic methods can be divided according to the encryption constitute a shift,affine,random categories.This paper replacement formula to decipher the encrypted ciphertext solvd mainly rely on the frequency distribution of the letters.For rotate each shift using the comparative statistics letters to determine the number of shifts plural on this basis so as the final number of shifts.For affine,random,you can not simply get all the various shifts in the number of locations.Only on this basis,therefore,the characteristics of high stability based on a large sample of data to determine the probability and statistics ranking the first two characters in the first two characters in the corresponding text appears.On this basis,the use of more than Euclid removed except Solving affine.Random encryption is used to find the data dictionary analysis.Finally get decrypted plaintext.The final result is solved for the shift,affine since the encryption is relatively simple to solve and change regularly so high accuracy rate,and need to compare a random basis,and therefore have a greater speed and accuracy uncertainty,while demand time than long.