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java encrypt
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‎bin/com/duwei/encrypt/FrequencyAnalysis$1.class‎

1.34 KB
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‎bin/com/duwei/encrypt/FrequencyAnalysis.class‎

5.62 KB
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‎bin/com/duwei/encrypt/MessageDigestTest.class‎

1.02 KB
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‎bin/com/duwei/encrypt/MyEncrypt.class‎

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‎bin/com/duwei/encrypt/RSA.class‎

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‎src/com/duwei/encrypt/FrequencyAnalysis.java‎

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package com.duwei.encrypt;
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import java.io.File;
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import java.io.FileReader;
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import java.io.FileWriter;
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import java.io.IOException;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.Map.Entry;
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/**
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* 频率分析法破解凯撒密码
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* http://blog.csdn.net/axi295309066/article/details/52491077
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*/
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public class FrequencyAnalysis {
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//英文里出现次数最多的字符
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private static final char MAGIC_CHAR = 'e';
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//破解生成的最大文件数
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private static final int DE_MAX_FILE = 4;
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public static void main(String[] args) throws Exception {
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//测试1，统计字符个数
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//printCharCount("article1_en.txt");
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//加密文件
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//int key = 3;
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//encryptFile("article1.txt", "article1_en.txt", key);
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//读取加密后的文件
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String artile = file2String("article1_en.txt");
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//解密（会生成多个备选文件）
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decryptCaesarCode(artile, "article1_de.txt");
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}
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public static void printCharCount(String path) throws IOException{
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String data = file2String(path);
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List<Entry<Character, Integer>> mapList = getMaxCountChar(data);
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for (Entry<Character, Integer> entry : mapList) {
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//输出前几位的统计信息
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System.out.println("字符'" + entry.getKey() + "'出现" + entry.getValue() + "次");
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}
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}
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public static void encryptFile(String srcFile, String destFile, int key) throws IOException {
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String artile = file2String(srcFile);
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//加密文件
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String encryptData = MyEncrypt.encrypt(artile, key);
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//保存加密后的文件
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string2File(encryptData, destFile);
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}
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/**
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* 破解凯撒密码
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* @param input 数据源
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* @return 返回解密后的数据
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*/
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public static void decryptCaesarCode(String input, String destPath) {
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int deCount = 0;//当前解密生成的备选文件数
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//获取出现频率最高的字符信息（出现次数越多越靠前）
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List<Entry<Character, Integer>> mapList = getMaxCountChar(input);
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for (Entry<Character, Integer> entry : mapList) {
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//限制解密文件备选数
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if (deCount >= DE_MAX_FILE) {
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break;
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}
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//输出前几位的统计信息
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System.out.println("字符'" + entry.getKey() + "'出现" + entry.getValue() + "次");
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++deCount;
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//出现次数最高的字符跟MAGIC_CHAR的偏移量即为秘钥
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int key = entry.getKey() - MAGIC_CHAR;
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System.out.println("猜测key = " + key + "， 解密生成第" + deCount + "个备选文件" + "\n");
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String decrypt = MyEncrypt.decrypt(input, key);
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String fileName = "de_" + deCount + destPath;
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string2File(decrypt, fileName);
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}
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}
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//统计String里出现最多的字符
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public static List<Entry<Character, Integer>> getMaxCountChar(String data) {
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Map<Character, Integer> map = new HashMap<Character, Integer>();
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char[] array = data.toCharArray();
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for (char c : array) {
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if(!map.containsKey(c)) {
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map.put(c, 1);
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}else{
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Integer count = map.get(c);
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map.put(c, count + 1);
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}
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}
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//输出统计信息
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/*for (Entry<Character, Integer> entry : map.entrySet()) {
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System.out.println(entry.getKey() + "出现" + entry.getValue() + "次");
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}*/
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//获取获取最大值
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int maxCount = 0;
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for (Entry<Character, Integer> entry : map.entrySet()) {
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//不统计空格
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if (/*entry.getKey() != ' ' && */entry.getValue() > maxCount) {
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maxCount = entry.getValue();
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}
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}
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//map转换成list便于排序
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List<Entry<Character, Integer>> mapList = new ArrayList<Map.Entry<Character,Integer>>(map.entrySet());
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//根据字符出现次数排序
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Collections.sort(mapList, new Comparator<Entry<Character, Integer>>(){
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@Override
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public int compare(Entry<Character, Integer> o1,
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Entry<Character, Integer> o2) {
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return o2.getValue().compareTo(o1.getValue());
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}
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});
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return mapList;
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}
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public static String file2String(String path) throws IOException {
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FileReader reader = new FileReader(new File(path));
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char[] buffer = new char[1024];
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int len = -1;
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StringBuffer sb = new StringBuffer();
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while ((len = reader.read(buffer)) != -1) {
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sb.append(buffer, 0, len);
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}
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return sb.toString();
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}
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public static void string2File(String data, String path){
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FileWriter writer = null;
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try {
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writer = new FileWriter(new File(path));
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writer.write(data);
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} catch (Exception e) {
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e.printStackTrace();
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}finally {
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if (writer != null) {
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try {
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writer.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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}
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}

‎src/com/duwei/encrypt/MessageDigestTest.java‎

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package com.duwei.encrypt;
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import java.security.MessageDigest;
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import java.security.NoSuchAlgorithmException;
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public class MessageDigestTest {
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/**
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* @param args
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*/
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public static void main(String[] args) {
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// TODO Auto-generated method stub
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}
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public void MDAl(String content){
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//常用算法：MD5、SHA、CRC
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MessageDigest digest = null;
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try {
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digest = MessageDigest.getInstance("MD5");
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} catch (NoSuchAlgorithmException e) {
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e.printStackTrace();
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}
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byte[] result = digest.digest(content.getBytes());
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//消息摘要的结果一般都是转换成16 进制字符串形式展示
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//String hex = Hex.encode(result);
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//MD5 结果为16 字节（128 个比特位）、转换为16 进制表示后长度是32 个字符
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//SHA 结果为20 字节（160 个比特位）、转换为16 进制表示后长度是40 个字符
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//System.out.println(hex);
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}
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}

‎src/com/duwei/encrypt/MyEncrypt.java‎

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package com.duwei.encrypt;
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public class MyEncrypt {
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public static void main(String[] args) {
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}
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/**
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* 加密
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* @param input 数据源（需要加密的数据）
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* @param key 秘钥，即偏移量
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* @return 返回加密后的数据
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*/
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public static String encrypt(String input, int key) {
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//得到字符串里的每一个字符
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char[] array = input.toCharArray();
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for (int i = 0; i < array.length; ++i) {
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//字符转换成ASCII 码值
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int ascii = array[i];
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//字符偏移，例如a->b
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ascii = ascii + key;
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//ASCII 码值转换为char
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char newChar = (char) ascii;
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//替换原有字符
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array[i] = newChar;
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//以上4 行代码可以简写为一行
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//array[i] = (char) (array[i] + key);
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}
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//字符数组转换成String
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return new String(array);
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}
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/**
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* 解密
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* @param input 数据源（被加密后的数据）
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* @param key 秘钥，即偏移量
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* @return 返回解密后的数据
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*/
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public static String decrypt(String input, int key) {
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//得到字符串里的每一个字符
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char[] array = input.toCharArray();
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for (int i = 0; i < array.length; ++i) {
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//字符转换成ASCII 码值
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int ascii = array[i];
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//恢复字符偏移，例如b->a
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ascii = ascii - key;
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//ASCII 码值转换为char
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char newChar = (char) ascii;
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//替换原有字符
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array[i] = newChar;
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//以上4 行代码可以简写为一行
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//array[i] = (char) (array[i] - key);
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}
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//字符数组转换成String
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return new String(array);
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}
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}

‎src/com/duwei/encrypt/RSA.java‎

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package com.duwei.encrypt;
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import java.security.InvalidKeyException;
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import java.security.KeyPair;
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import java.security.KeyPairGenerator;
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import java.security.NoSuchAlgorithmException;
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import java.security.PrivateKey;
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import java.security.PublicKey;
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import javax.crypto.BadPaddingException;
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import javax.crypto.Cipher;
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import javax.crypto.IllegalBlockSizeException;
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import javax.crypto.NoSuchPaddingException;
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public class RSA {
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//一次性加密数据的长度不能大于117 字节
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private static final int ENCRYPT_BLOCK_MAX = 117;
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//一次性解密的数据长度不能大于128 字节
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private static final int DECRYPT_BLOCK_MAX = 128;
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public static void main(String[] args) {
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}
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/**
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* RSA加密解密API
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* @param content
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*/
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public void encryptRsa(String content) {
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try {
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// 1，获取cipher 对象
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Cipher cipher = Cipher.getInstance("RSA");
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// 2，通过秘钥对生成器KeyPairGenerator 生成公钥和私钥
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KeyPair keyPair = KeyPairGenerator
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.getInstance("RSA")
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.generateKeyPair();
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PublicKey publicKey = keyPair.getPublic();//公钥
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PrivateKey privateKey = keyPair.getPrivate();//私钥
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// 3,使用公钥初始化密码器
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cipher.init(Cipher.ENCRYPT_MODE, publicKey);
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// 4，执行加密操作
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byte[] result = cipher.doFinal(content.getBytes());
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// 使用私钥初始化密码器
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cipher.init(Cipher.DECRYPT_MODE, privateKey);
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// 执行解密操作
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byte[] deResult = cipher.doFinal(result);
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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}

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