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package io.github.util.encryption;

import org.apache.tomcat.util.codec.binary.Base64;

import javax.crypto.Cipher;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;
import java.security.*;
import java.security.spec.RSAPrivateCrtKeySpec;
import java.security.spec.RSAPublicKeySpec;

/**
 *    Genius

 **/
public class RSAEncryptionUtils implements EncryptionUtil {

    /** 指定加密算法为DESede */
    private String ALGORITHM = "RSA";
    /** 指定key的大小 */
    private int KEYSIZE = 1024;
    /** 指定公钥存放文件 */
    private String PUBLIC_KEY_FILE = "./src/main/resources/public.keystore";
    /** 指定私钥存放文件 */
    private String PRIVATE_KEY_FILE = "./src/main/resources/private.keystore";

    /**
     * 生成密钥对
     */
    private void generateKeyPair() throws Exception {
        /** RSA算法要求有一个可信任的随机数源 */
        SecureRandom sr = new SecureRandom();
        /** 为RSA算法创建一个KeyPairGenerator对象 */
        KeyPairGenerator kpg = KeyPairGenerator.getInstance(ALGORITHM);
        /** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */
        kpg.initialize(KEYSIZE, sr);
        /** 生成密匙对 */
        KeyPair kp = kpg.generateKeyPair();
        /** 得到公钥 */
        Key publicKey = kp.getPublic();
        /** 得到私钥 */
        Key privateKey = kp.getPrivate();
        /** 用对象流将生成的密钥写入文件 */
        ObjectOutputStream oos1 = new ObjectOutputStream(new FileOutputStream(PUBLIC_KEY_FILE));
        ObjectOutputStream oos2 = new ObjectOutputStream(new FileOutputStream(PRIVATE_KEY_FILE));
        oos1.writeObject(publicKey);
        oos2.writeObject(privateKey);
        /** 清空缓存，关闭文件输出流 */
        oos1.close();
        oos2.close();
    }

    /**
     * 生成密钥对字符串
     */
    private void generateKeyPairString() throws Exception {
        /** RSA算法要求有一个可信任的随机数源 */
        SecureRandom sr = new SecureRandom();
        /** 为RSA算法创建一个KeyPairGenerator对象 */
        KeyPairGenerator kpg = KeyPairGenerator.getInstance(ALGORITHM);
        /** 利用上面的随机数据源初始化这个KeyPairGenerator对象 */
        kpg.initialize(KEYSIZE, sr);
        /** 生成密匙对 */
        KeyPair kp = kpg.generateKeyPair();
        /** 得到公钥 */
        Key publicKey = kp.getPublic();
        /** 得到私钥 */
        Key privateKey = kp.getPrivate();
        /** 用字符串将生成的密钥写入文件 */

        String algorithm = publicKey.getAlgorithm(); // 获取算法
        KeyFactory keyFact = KeyFactory.getInstance(algorithm);
        BigInteger prime = null;
        BigInteger exponent = null;

        RSAPublicKeySpec keySpec = (RSAPublicKeySpec) keyFact.getKeySpec(publicKey, RSAPublicKeySpec.class);

        RSAPrivateCrtKeySpec privateKeySpec = (RSAPrivateCrtKeySpec) keyFact.getKeySpec(privateKey,
                RSAPrivateCrtKeySpec.class);


    }
    @Override
    public String Encipher(String password) throws Exception {
        generateKeyPair();
        /** 将文件中的公钥对象读出 */
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));
        Key key = (Key) ois.readObject();
        ois.close();

        String algorithm = key.getAlgorithm(); // 获取算法
        KeyFactory keyFact = KeyFactory.getInstance(algorithm);
        BigInteger prime = null;
        BigInteger exponent = null;
        if ("RSA".equals(algorithm)) { // 如果是RSA加密
            RSAPublicKeySpec keySpec = (RSAPublicKeySpec) keyFact.getKeySpec(key, RSAPublicKeySpec.class);
        }

        /** 得到Cipher对象来实现对源数据的RSA加密 */
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        byte[] b = password.getBytes();
        /** 执行加密操作 */
        byte[] b1 = cipher.doFinal(b);
        return Base64.encodeBase64String(b1);
    }

    @Override
    public String Decrypt(String password) throws Exception{
        /** 将文件中的私钥对象读出 */
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));
        Key key = (Key) ois.readObject();

        String algorithm = key.getAlgorithm(); // 获取算法
        KeyFactory keyFact = KeyFactory.getInstance(algorithm);
        RSAPrivateCrtKeySpec privateKeySpec = (RSAPrivateCrtKeySpec) keyFact.getKeySpec(key,
                RSAPrivateCrtKeySpec.class);
        BigInteger privateModulus = privateKeySpec.getModulus();
        BigInteger privateExponent = privateKeySpec.getPrivateExponent();


        /** 得到Cipher对象对已用公钥加密的数据进行RSA解密 */
        Cipher cipher = Cipher.getInstance(ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, key);

        byte[] b1 = Base64.decodeBase64(password);
        /** 执行解密操作 */
        byte[] b = cipher.doFinal(b1);
        return new String(b);
    }
}