md5加密，盐

import java.security.MessageDigest;
public static String MD5(String key) {
        char hexDigits[] = {
                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
        };
        try {
            byte[] btInput = key.getBytes();
            // 获得MD5摘要算法的 MessageDigest 对象
            MessageDigest mdInst = MessageDigest.getInstance("MD5");
            // 使用指定的字节更新摘要
            mdInst.update(btInput);
            // 获得密文
            byte[] md = mdInst.digest();
            // 把密文转换成十六进制的字符串形式
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
            logger.error("生成MD5失败", e);
            return null;
        }
        public static void main(String[] args) {
		String password = "12345";
		String md5password = MD5(password);
		System.out.println(md5password);//827CCB0EEA8A706C4C34A16891F84E7B
	}
    }

不足之处,通过大量的对比，可以解密,所以引入盐的概念.salt

package md5;

import java.security.MessageDigest;
import java.util.UUID;

public class Md5Test {
	public static String MD5(String key) {
        char hexDigits[] = {
                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
        };
        try {
            byte[] btInput = key.getBytes();
            // 获得MD5摘要算法的 MessageDigest 对象
            MessageDigest mdInst = MessageDigest.getInstance("MD5");
            // 使用指定的字节更新摘要
            mdInst.update(btInput);
            // 获得密文
            byte[] md = mdInst.digest();
            // 把密文转换成十六进制的字符串形式
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte byte0 = md[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            return new String(str);
        } catch (Exception e) {
        	System.out.println("加密生成失败");
            e.printStackTrace();
            return null;
        }
    }
	public static String getSalt() {
		String salt=UUID.randomUUID().toString().replaceAll("-","").substring(0, 10);
		return salt;
		
	}
	
	public static void main(String[] args) {
		String password = "12345";
		String salt = getSalt();
		String md5password = MD5(password+salt);
		System.out.println(salt);
		System.out.println("salt,md5加密后的密码"+md5password);
		System.out.println("............");
		String  loginpassword = "123";
		boolean result = MD5(loginpassword+salt).equals(md5password);
		System.out.println(result);
	}
	
}

shiro自带的带盐加密n次 

package md5;
import org.apache.shiro.crypto.SecureRandomNumberGenerator;
import org.apache.shiro.crypto.hash.SimpleHash;


public class shiroMd5 {
	public static void main(String[] args) {
	        String password = "123";
	        String salt = new SecureRandomNumberGenerator().nextBytes().toString();
	        int times = 2;
	        String algorithmName = "md5";
	         
	        String encodedPassword = new SimpleHash(algorithmName,password,salt,times).toString();
	         
	        System.out.printf("原始密码是 %s , 盐是： %s, 运算次数是： %d, 运算出来的密文是：%s ",password,salt,times,encodedPassword);
	         
	    }
	
}

Shiro 整合加密

数据库调整

user表加入salt字段
alter table user add (salt varchar(100) )