RSA非对称加密和MD5不可逆加密代码示例

加密算法可以分为三大类：

• 对称加密算法:DES 
• 非对称加密算法: RSA
• Hash算法: MD5

登陆密码加密流程:

web端用公钥加密密码,server端用私钥解码,将解出的明文用MD5加密后存入数据库或与数据库的密码比较,这种方式会有中间人攻击的问题,只能用https方式,

如果用http方式,需要在web端生成公钥和私钥,将公钥发给server端,server端生成一串随机字符串并用公钥加密发给web端,web端用私钥解码并拼接上密码组成新的

字符串,将随机字符串作为AES加密算法的密码对密码进行加密发送给server端,server端使用随机字符串对新的字符串进行解密,server端系解析解密后的字符串，校验随机字符串是否一致.

RSA:

package login;

import javax.crypto.Cipher;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;

public class RSAUtil {
    static final Base64.Decoder decoder = Base64.getDecoder();
    static final Base64.Encoder encoder = Base64.getEncoder();

    public static void main(String[] args) throws Exception {
        // 随机生成一对密钥（包含公钥和私钥）
        KeyPair keyPair = generateKeyPair();
        // 获取 公钥 和 私钥
        RSAPublicKey pubKey = (RSAPublicKey) keyPair.getPublic();
        // 创建 已编码的公钥规格
        X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(pubKey.getEncoded());
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);

        RSAPrivateKey priKey = (RSAPrivateKey) keyPair.getPrivate();
        // 创建 已编码的私钥规格
        PKCS8EncodedKeySpec pkcs8EncodedKeySpec5 = new PKCS8EncodedKeySpec(priKey.getEncoded());
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec5);
        // 原文数据
        String data = "你好, World!";
        // 客户端: 用公钥加密原文, 返回加密后的数据
        byte[] cipherData = encrypt(data.getBytes(), publicKey);
        // 服务端: 用私钥解密数据, 返回原文
        byte[] plainData = decrypt(cipherData, privateKey);
        // 输出密文
        System.out.println(new String(cipherData));
        // 输出查看解密后的原文
        System.out.println(new String(plainData));  // 结果打印: 你好, World
    }



    /**
     * 随机生成密钥对（包含公钥和私钥）
     */
    private static KeyPair generateKeyPair() throws Exception {
        // 获取指定算法的密钥对生成器
        KeyPairGenerator gen = KeyPairGenerator.getInstance("RSA");
        // 初始化密钥对生成器（密钥长度要适中, 太短不安全, 太长加密/解密速度慢）
        gen.initialize(2048);
        // 随机生成一对密钥（包含公钥和私钥）
        KeyPair keyPair = gen.generateKeyPair();
        RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
        RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();
        //公钥私钥base64编码
        String publicKeyString = new String(encoder.encode(rsaPublicKey.getEncoded()));
        String privateKeyString = new String(encoder.encode(rsaPrivateKey.getEncoded()));
        return keyPair;
    }
    /**
     * 公钥加密数据
     */
    private static byte[] encrypt(byte[] plainData, PublicKey pubKey) throws Exception {
        // 获取指定算法的密码器
        Cipher cipher = Cipher.getInstance("RSA");
        // 初始化密码器（公钥加密模型）
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        // 加密数据, 返回加密后的密文
        return cipher.doFinal(plainData);
    }
    /**
     * 私钥解密数据
     */
    private static byte[] decrypt(byte[] cipherData, PrivateKey priKey) throws Exception {
        // 获取指定算法的密码器
        Cipher cipher = Cipher.getInstance("RSA");
        // 初始化密码器（私钥解密模型）
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        // 解密数据, 返回解密后的明文
        return cipher.doFinal(cipherData);
    }

}

MD5加盐:

package login;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class PasswordEncoder {
    private final static String[] hexDigits = { "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
 
    private Object salt;
    private String algorithm;
 
    public PasswordEncoder(Object salt, String algorithm) {
        this.salt = salt;
        this.algorithm = algorithm;
    }
 
    public String encode(String rawPass) {
        String result = null;
        try {
            //参数可以是"MD5"，"SHA"等
            MessageDigest md = MessageDigest.getInstance(algorithm);
            //加密后的字符串
            result = byteArrayToHexString(md.digest(mergePasswordAndSalt(rawPass).getBytes("utf-8")));
        } catch (Exception ex) {
        }
        return result;
    }
 
    public boolean isPasswordValid(String encPass, String rawPass) {
        String pass1 = "" + encPass;
        String pass2 = encode(rawPass);
 
        return pass1.equals(pass2);
    }
 
    private String mergePasswordAndSalt(String password) {
        if (password == null) {
            password = "";
        }
 
        if ((salt == null) || "".equals(salt)) {
            return password;
        } else {
            return password + "{" + salt.toString() + "}";
        }
    }
 
    /**
     * 转换字节数组为16进制字串
     * @param b 字节数组
     * @return 16进制字串
     */
    private static String byteArrayToHexString(byte[] b) {
        StringBuffer resultSb = new StringBuffer();
        for (int i = 0; i < b.length; i++) {
            resultSb.append(byteToHexString(b[i]));
        }
        return resultSb.toString();
    }
 
    private static String byteToHexString(byte b) {
        int n = b;
        if (n < 0)
            n = 256 + n;
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }
 
 
    public static void main(String[] args) throws NoSuchAlgorithmException, UnsupportedEncodingException {
        String salt = "be5e0323a9195ade5f56695ed9f2eb6b036f3e6417115d0cbe2fb9d74d8740406838dc84f152014b39a2414fb3530a40bc028a9e87642bd03cf5c36a1f70801e";
        PasswordEncoder encoderMd5 = new PasswordEncoder(salt, "MD5");
        String encode = encoderMd5.encode("zxp52077");
        System.out.println(encode);
        boolean passwordValid = encoderMd5.isPasswordValid("c21feb87d79fd42e4336e4c231785ff9", "test");
        System.out.println(passwordValid);
 
        PasswordEncoder encoderSha = new PasswordEncoder(salt, "SHA");
        String pass2 = encoderSha.encode("test");
        System.out.println(pass2);
        boolean passwordValid2 = encoderSha.isPasswordValid("409cf43cbdc92e1979018b2e2fdc60c7f07673e9", "test");
        System.out.println(passwordValid2);


    }
 
}