加解密：编码算法、哈希算法

• url编码

Java标准库提供了一个URLEncoder类来对任意字符串进行URL编码
 
# 加密
public class Main {
    public static void main(String[] args) {
        String encoded = URLEncoder.encode("中文!", StandardCharsets.UTF_8);
        System.out.println(encoded);
    }
}
# 控制台
%E4%B8%AD%E6%96%87%21
 
# 解密
public class Main {
    public static void main(String[] args) {
        String decoded = URLDecoder.decode("%E4%B8%AD%E6%96%87%21", StandardCharsets.UTF_8);
        System.out.println(decoded);
    }
}
# 控制台
中文!

• Base64编码

Base64编码可以把任意长度的二进制数据变为纯文本
 
# 加密
public class Main {
    public static void main(String[] args) {
        byte[] input = new byte[] { (byte) 0xe4, (byte) 0xb8, (byte) 0xad };
        String b64encoded = Base64.getEncoder().encodeToString(input);
        System.out.println(b64encoded);
    }
}
# 控制台
5Lit
 
# 解密
public class Main {
    public static void main(String[] args) {
        byte[] output = Base64.getDecoder().decode("5Lit");
        System.out.println(Arrays.toString(output)); 
    }
}
# 控制台
[-28, -72, -83]
 
# 数组长度不是3的整数时，加密
public class Main {
    public static void main(String[] args) {
        byte[] input = new byte[] { (byte) 0xe4, (byte) 0xb8, (byte) 0xad, 0x21 };
        String b64encoded = Base64.getEncoder().encodeToString(input);
        String b64encoded2 = Base64.getEncoder().withoutPadding().encodeToString(input);
        System.out.println(b64encoded);
        System.out.println(b64encoded2);
        byte[] output = Base64.getDecoder().decode(b64encoded2);
        System.out.println(Arrays.toString(output));
    }
}
# 控制台
5LitIQ==
5LitIQ
[-28, -72, -83, 33]
 
# 针对URL的Base64编码
public class Main {
    public static void main(String[] args) {
        byte[] input = new byte[] { 0x01, 0x02, 0x7f, 0x00 };
        String b64encoded = Base64.getUrlEncoder().encodeToString(input);
        System.out.println(b64encoded);
        byte[] output = Base64.getUrlDecoder().decode(b64encoded);
        System.out.println(Arrays.toString(output));
    }
}
# 控制台
AQJ_AA==
[1, 2, 127, 0]

• 常用哈希算法

算法	输出长度（位）	输出长度（字节）
MD5	128 bits	16 bytes
SHA-1	160 bits	20 bytes
RipeMD-160	160 bits	20 bytes
SHA-256	256 bits	32 bytes
SHA-512	512 bits	64 bytes

• md5加密

public class Main {
    public static void main(String[] args) throws Exception {
        // 创建一个MessageDigest实例:
        MessageDigest md = MessageDigest.getInstance("MD5");
        // 反复调用update输入数据:
        md.update("Hello".getBytes("UTF-8"));
        md.update("World".getBytes("UTF-8"));
        byte[] result = md.digest(); // 16 bytes: 68e109f0f40ca72a15e05cc22786f8e6
        System.out.println(new BigInteger(1, result).toString(16));
    }
}
# 控制台
68e109f0f40ca72a15e05cc22786f8e6

• md5加密、加盐

package com.md5.demo;
 
import java.security.MessageDigest;
import java.util.Random;
 
import org.apache.commons.codec.binary.Hex;
/**
 * MD5加盐加密
 */ 
public class PasswordUtil {
    /**
     * 生成含有随机盐的密码
     */
    public static String generate(String password) {
        Random r = new Random();
        StringBuilder sb = new StringBuilder(16);
        sb.append(r.nextInt(99999999)).append(r.nextInt(99999999));
        int len = sb.length();
        if (len < 16) {
            for (int i = 0; i < 16 - len; i++) {
                sb.append("0");
            }
        }
        String salt = sb.toString();
        password = md5Hex(password + salt);
        char[] cs = new char[48];
        for (int i = 0; i < 48; i += 3) {
            cs[i] = password.charAt(i / 3 * 2);
            char c = salt.charAt(i / 3);
            cs[i + 1] = c;
            cs[i + 2] = password.charAt(i / 3 * 2 + 1);
        }
        return new String(cs);
    }
 
    /**
     * 校验密码是否正确
     */
    public static boolean verify(String password, String md5) {
        char[] cs1 = new char[32];
        char[] cs2 = new char[16];
        for (int i = 0; i < 48; i += 3) {
            cs1[i / 3 * 2] = md5.charAt(i);
            cs1[i / 3 * 2 + 1] = md5.charAt(i + 2);
            cs2[i / 3] = md5.charAt(i + 1);
        }
        String salt = new String(cs2);
        return md5Hex(password + salt).equals(new String(cs1));
    }
 
    /**
     * 获取十六进制字符串形式的MD5摘要
     */
    public static String md5Hex(String src) {
        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            byte[] bs = md5.digest(src.getBytes());
            return new String(new Hex().encode(bs));
        } catch (Exception e) {
            return null;
        }
    }
}
 
# 测试
    public static void main(String[] args) {
        // 加密+加盐
        String password1 = generate("admin");
        System.out.println("结果：" + password1 + "   长度："+ password1.length());
        // 解码
        System.out.println(verify("admin", password1));
 
        // 加密+加盐
        String password2= generate("admin");
        System.out.println("结果：" + password2 + "   长度："+ password2.length());
        // 解码
        System.out.println(verify("admin", password2));
    }

• 生成随机盐

//length用户要求，随机产生字符串的长度
public static String getRandomString(int length){
    String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    Random random=new Random();
    StringBuffer sb=new StringBuffer();
    for(int i=0;i<length;i++){
        int number=random.nextInt(62);
        sb.append(str.charAt(number));
    }
    return sb.toString();
}

• 加密、加盐

# 利用Apache commons的DigestUtils工具类
String password1 = DigestUtils.md5Hex(stu1.name+stu1.password+stu1.email);
System.out.println(password1);
 
# 反复加盐
String password1 = DigestUtils.md5Hex(stu1.name+stu1.password+stu1.email);
DigestUtils.md5Hex(DigestUtils.md5Hex("774"+password1+"@@__"));

public class Main {
    public static void main(String[] args) throws Exception {
        // 创建一个MessageDigest实例:
        MessageDigest md = MessageDigest.getInstance("SHA-1");
        // 反复调用update输入数据:
        md.update("Hello".getBytes("UTF-8"));
        md.update("World".getBytes("UTF-8"));
        byte[] result = md.digest(); // 20 bytes: db8ac1c259eb89d4a131b253bacfca5f319d54f2
        System.out.println(new BigInteger(1, result).toString(16));
    }
}
# 控制台
db8ac1c259eb89d4a131b253bacfca5f319d54f2

• SHA-256加密

public class Test1 {
 
    public static void main(String[] args) throws Exception {
        // 创建一个MessageDigest实例:
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        // 反复调用update输入数据:
        md.update("Hello".getBytes("UTF-8"));
        md.update("World".getBytes("UTF-8"));
        byte[] result = md.digest(); // 20 bytes: db8ac1c259eb89d4a131b253bacfca5f319d54f2
        System.out.println(new BigInteger(1, result).toString(16));
    }
 
}
# 控制台
872e4e50ce9990d8b041330c47c9ddd11bec6b503ae9386a99da8584e9bb12c4

• SHA-512加密

public class Test1 {
 
    public static void main(String[] args) throws Exception {
        // 创建一个MessageDigest实例:
        MessageDigest md = MessageDigest.getInstance("SHA-512");
        // 反复调用update输入数据:
        md.update("Hello".getBytes("UTF-8"));
        md.update("World".getBytes("UTF-8"));
        byte[] result = md.digest(); // 20 bytes: db8ac1c259eb89d4a131b253bacfca5f319d54f2
        System.out.println(new BigInteger(1, result).toString(16));
    }
 
}
# 控制台
8ae6ae71a75d3fb2e0225deeb004faf95d816a0a58093eb4cb5a3aa0f197050d7a4dc0a2d5c6fbae5fb5b0d536a0a9e6b686369fa57a027687c3630321547596