Java implementation MD5 encryption and decryption of code instance sharing _java

Foundation: The use of messagedigest classes

In fact, in Java to complete MD5 encryption, messagedigest most of the class to help you achieve good, a few lines of code enough:

/**
 * For string MD5 encryption
 *
 @param str
 * @return
/import java.security.MessageDigest;
public static string getMD5 (String str) {
 try {
 //Generate a MD5 Cryptographic Calculation digest
 messagedigest MD = Messagedigest.getinstance ("MD5");
 Compute the MD5 function
 md.update (str.getbytes ());
 Digest () finally determines that the MD5 hash value is returned and the return value is 8 as a string. Because the MD5 hash value is a 16-bit hex value, it is actually a 8-bit character
 //BigInteger function that converts a 8-bit string into a 16-bit hex value, represented by a string; hash value in string form return
 new BigInteger (1, Md.digest ()). ToString ();
 catch (Exception e) {
 throw new Speedexception ("MD5 encryption Error");
 }

Advanced: Encryption and Decryption class
Java Implementation MD5 encryption and decryption class, with the test class, see Code.

MD5 encryption decryption class--mymd5util, code as follows

Package com.zyg.security.md5;
Import java.io.UnsupportedEncodingException;
Import Java.security.MessageDigest;
Import java.security.NoSuchAlgorithmException;
Import Java.security.SecureRandom;

Import Java.util.Arrays;
 public class Mymd5util {private static final String hex_nums_str= "0123456789ABCDEF";
 
 private static final Integer salt_length = 12; /** * Converts a 16-string into a byte array * @param hex * @return/public static byte[] Hexstringtobyte (string hex) {int len = (he
 X.length ()/2);
 Byte[] result = new Byte[len];
 char[] Hexchars = Hex.tochararray ();
 for (int i = 0; i < len; i++) {int pos = i * 2; Result[i] = (byte) (Hex_nums_str.indexof (Hexchars[pos)) << 4 |
 Hex_nums_str.indexof (Hexchars[pos + 1]));
 return result; /** * Converts the specified byte array to a 16-character string * @param b * @return/public static string bytetohexstring (byte[] b) {Stringbuffe
 R hexstring = new StringBuffer (); for (int i = 0; i < b.length i++) {String hex = integer.tohexstring (b[i) &0xFF);
 if (hex.length () = = 1) {hex = ' 0 ' + hex;
 } hexstring.append (Hex.touppercase ());
 return hexstring.tostring (); /** * Verify password is valid * @param password * @param passwordindb * @return * @throws nosuchalgorithmexception * @throws U Nsupportedencodingexception */public static Boolean Validpassword (string password, string passwordindb) throws Nosucha Lgorithmexception, Unsupportedencodingexception {//convert 16 string format password to byte array byte[] pwdindb = Hexstringtobyte (passwordindb
 );
 Declare salt variable byte[] Salt = new Byte[salt_length];
 Extract the salt from the password byte array stored in the database system.arraycopy (pwdindb, 0, salt, 0, salt_length);
 Create a message digest object MessageDigest MD = messagedigest.getinstance ("MD5");
 The salt data is passed into the Message digest object Md.update (salt);
 Pass the password's data to the Message Digest object Md.update (Password.getbytes ("UTF-8"));
 Generates a message digest for the input password byte[] Digest = Md.digest ();
 Declares a variable byte[] that holds the password message digest in the database digestindb = new Byte[pwdindb.length-salt_length];
 Gets the message digest for the password in the database system.arraycopy (pwdindb, Salt_length, digestindb, 0, digestindb.length); ThanThe message digest based on the input password and the message digest in the database are the same if (Arrays.equals (Digest, DIGESTINDB)) {//password correctly returns the password matching message return true;
 else {//password incorrect return password mismatch message returns false; /** * Obtains encrypted 16-in-form password * @param password * @return * @throws nosuchalgorithmexception * @throws Unsupportedenco Dingexception */public static string Getencryptedpwd (string password) throws NoSuchAlgorithmException, Unsupportedenco
 dingexception {///declares the encrypted password array variable byte[] pwd = null;
 Random number generator SecureRandom random = new SecureRandom ();
 Declare salt array variable byte[] Salt = new Byte[salt_length];

 Put the random number into the salt variable random.nextbytes (salt);
 Declares a message digest object MessageDigest MD = NULL;
 Create message Digest MD = messagedigest.getinstance ("MD5");
 The salt data is passed into the Message digest object Md.update (salt);
 Pass the password's data to the Message Digest object Md.update (Password.getbytes ("UTF-8"));

 Gets the byte array of the message digest byte[] Digest = Md.digest ();
 Because you want to store the salt in the byte array of the password, add the byte length of the salt pwd = new Byte[digest.length + salt_length];
 Copies the byte of the salt to the first 12 bytes of the generated encrypted password byte array so that the salt system.arraycopy (salts, 0, pwd, 0, salt_length) are removed when the password is validated; Copy message digest to encrypted password byte array from 13th wordSection begins with Byte System.arraycopy (digest, 0, pwd, salt_length, digest.length);
 Converts the password in the encrypted byte array format to the password return bytetohexstring (PWD) in the 16 string format;

 }
}

Test class--client, code as follows:

Package com.zyg.security.md5;
Import java.io.UnsupportedEncodingException;
Import java.security.NoSuchAlgorithmException;
Import Java.util.HashMap;

Import Java.util.Map;
 
 public class Client {private static MAP users = new HashMap ();
 public static void Main (string[] args) {String userName = "Zyg";
 String Password = "123";
 
 RegisterUser (Username,password);
 UserName = "Changong";
 Password = "456";
 
 RegisterUser (Username,password);
 String Loginuserid = "Zyg";
 String pwd = "1232"; try {if (Loginvalid (loginuserid,pwd)) {System.out.println ("Welcome to LOGIN!!!")
 "); }else{System.out.println ("Password error, please re-enter!!!
 ");
 The catch (NoSuchAlgorithmException e) {//TODO auto-generated catch block E.printstacktrace ();
 catch (Unsupportedencodingexception e) {//TODO auto-generated catch block E.printstacktrace ();  }/** * Registered user * * @param userName * @param password * * public static void RegisterUser (String username,string
 Password) {String encryptedpwd = null; try {Encryptedpwd = mymd5util.getencryptedpwd (password);
 
 Users.put (UserName, encryptedpwd);
 catch (NoSuchAlgorithmException e) {//TODO auto-generated catch block E.printstacktrace ();
 catch (Unsupportedencodingexception e) {//TODO auto-generated catch block E.printstacktrace (); }/** * Verify login * * @param userName * @param password * @return * @throws unsupportedencodingexception * @thro WS NoSuchAlgorithmException */public static Boolean loginvalid (String username,string password) throws Nosuchalgorit
 Hmexception, unsupportedencodingexception{String pwdindb = (string) users.get (userName);
 if (NULL!=PWDINDB) {//the user exists return Mymd5util.validpassword (password, pwdindb); }else{System.out.println ("The user is not present!!!
 ");
 return false;
 }
 }
}

PS: Here again for you to provide 2 MD5 encryption tools, interested friends can refer to:

MD5 Online Encryption Tool:

Http://tools.jb51.net/password/CreateMD5Password

Online md5/hash/sha-1/sha-2/sha-256/sha-512/sha-3/ripemd-160 Encryption Tool:

Http://tools.jb51.net/password/hash_md5_sha