Implementation principle of MD5 encryption algorithm
of MD5 encryption algorithm in Java:
public class MD5 { // 全局数组 private final static String[] strDigit = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"}; public class MD5 { } // 返回形式为数字和字符串 private static String byteToArrayString(byte bByte) { int iRet = bByte; if (iRet < 0) { iRet += 256; } int iD1 = iRet / 16; int iD2 = iRet % 16; return strDigits[iD1] + strDigits[iD2]; } // 返回形式只为数字 private static String byteToNum(byte bByte) { int iRet = bByte; if (iRet < 0) { iRet += 256; } return String.valueOf(iRet); } // 将字节数组转换成为16进制的字符串 private static String byteToString(byte[] bByte) { StringBuffer stringBuffer = new StringBuffer(); for (int i; i < bByte.length; i++) { StringBuffer.append(byteToArrayString(bByte[i])); } return stringBuffer.toString(); } // 获取MD5值 public static String GetMD5Code(String strObj) { String resultString = null; try { resultString = new String(); MessageDigest md5 = MessageDigest.getInstance("MD5"); // md5.digest() - 返回值为存放Hash值结果的byte数组 resultString = byteToString(md5.digest(strObj.getBytes())); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } return resultString; } }MessageDigest class
MessageDigest class:
- Provides the function of information digest algorithm for applications. Such as MD5 algorithm and SHA algorithm
- The message digest is a secure one-way Hash function : Receives data of any size and outputs a fixed-length Hash value
update
- The MessageDigest object is initialized at the beginning
The object processes data by calling update() method
/** * 使用指定的byte数组更新摘要 * * @param input 指定的byte数组 */ public void update(byte[] input);reset
The digest can be reset at any time by calling reset() method
digest
- Once the data to be updated has been updated, the digest() method should be called to complete the Hash calculation
For a given amount of updated data , the digest() method can only be called once. After calling the digest() method, the MessageDigest object is reset to its initial state
/** * 通过执行诸如填充之类的最终操作完成Hash计算. * 在调用此方法之后,摘要被重置 * * @return byte[] Hash计算后的byte数组 */ public byte[] digest();isEqual
/** * 比较两个摘要的相等性.做简单的字节比较 * * @param digestA 比较的摘要字节数组A * @param digestB 比较的摘要字节数组B * @return boolean 是否相等 */ public static boolean isEqual(byte[] digestA, byte[] digestB);getInstance
Returns a MessageDigest object implementing the specified digest algorithm
/** * 返回实现指定摘要算法的MessageDigest对象 * * @param algorithm 请求的算法的名称 * @param provider 提供者名称 * @return MessageDigest 指定摘要算法的MessageDigest对象 * @throws NoSuchAlgorithmException 当指定的请求算法名称不存在时抛出异常 */ public static MessageDigest getInstance(String algorithm) throws NoSuchAlgorithmException; /** * 返回实现指定摘要算法的MessageDigest对象 * * @param algorithm 请求算法的名称 * @return MessageDigest 指定摘要算法的MessageDigest对象 * @throws NoSuchAlgorithmException 当指定的请求算法名称不存在时抛出异常 */ public static MessageDigest getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException;- Provider The list of registered providers can be obtained through the getProviders() method of java.security.Security
Common algorithms provided by SUN:
- MD2
- MD5
- SHA-1
- SHA-256
- SHA-384
SHA-512
MD5 encryption algorithm for strings
Use Java's own MessageDigest to implement the MD5 encryption algorithm for text:
/** * 将字符串转换为MD5 */ public class ParseMD5 { public static String parseStrToMd5L32(String str) { // 将字符串转换为32位小写MD5 String reStr = null; try { MessageDigest md5 = MessageDigest.getInstance("MD5"); byte[] bytes = md5.digest(str.getBytes()); StringBuffer stringBuffer = new StringBuffer(); for (byte b : bytes) { int bt = b&0xff; if (bt < 16) { stringBuffer.append(0); } stringBuffer.append(Integer.toHexString(bt)); } reStr = stringBuffer.toString(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } return reStr; } // 将字符串转换为32位大写的MD5 public static String parseStrToMd5U32(String str) { String reStr = parseStrToMd5L32(str); if (reStr != null) { reStr = reStr.toUpperCase(); } return resStr; } // 将字符串转换为16位小写的MD5 public static String parseStrToMd5L16(String str) { String reStr = paseStrToMd5L32(str); if (reStr != null) { reStr = reStr.subString(8, 24); } return reStr; } // 将字符串转换为16位大写的MD5 public static String parseStrToMd5U16(String str) { String reStr = parseStrToMd5L32(str); if (reStr != null) { reStr = reStr.toUpperCase().subString(8, 24); } return reStr; } }MD5 encryption tool for text
Java provides the built-in MessageDigest to implement the encryption algorithm for text. The MD5 encryption tool class for encrypting text is as follows:
public class MD5Util { // 将文本转换为32位小写的MD5 public static String textToMd5L32(String plainText) { String result = null; // 判断需要转换的文本是否为空 if (StringUtils.isBlank(plainText)) { return null; } try { // 进行实例化和初始化 MessageDigest md5 = MessageDigest.getInstance("MD5"); // 得到一个操作系统默认的字节编码格式的字节数组 byte[] byteInput = plainText.getBytes(); // 对得到的字节数组进行处理 md5.update(byteInput); // 进行Hash计算并得到返回结果 byte[] btResult = md5.digest(); // 得到进行Hash计算后数据的长度 StringBuffer stringBuffer = new StringBuffer(); for (byte b : btResult) { int bt = b&0xff; if (bt < 16) { stringBuffer.append(0); } stringBuffer.append(Integer.toHexString(bt)); } reStr = stringBuffer.toString(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } return reStr; } // 将文本转换为32位大写的MD5 public static String textToMd5U32(String plainText) { if (StringUtils.isBlank(plainText)) { return null; } String result = textToMd5L32(plainText); result = result.toUpperCase(); return result; } }
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