凯撒加密解密

• 古罗马大帝凯撒发明:对字符串偏移

 

 

 

public static String encrypt(String str, int key) {        StringBuilder stringBuilder = new StringBuilder();        char[] array = str.toCharArray();        for (char c : array) {            int value = c;            value += key;            char cs = (char) value;            stringBuilder.append(cs);        }        return stringBuilder.toString();    }

 

public static String decryp(String str, int key) {        StringBuilder stringBuilder = new StringBuilder();        char[] array = str.toCharArray();        for (char c : array) {            int value = c;            value -= key;            char cs = (char) value;            stringBuilder.append(cs);        }        return stringBuilder.toString();    }

 

频度分析法破解凯撒加密算法

• 根据统计学破解凯撒算法：一篇英文文章字母e出现的概率很高