package com.tebon.ams.util;

import org.apache.commons.codec.binary.Base64;
import org.apache.log4j.Logger;

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.HashMap;
import java.util.Map;

/**
 * @description: ${description}
 * @author: dfz
 * @create: 2019-05-16
 **/
public class RSA {
    private static Logger logger = Logger.getLogger(RSA.class);

    private static final String KEY_ALGORITHM = "RSA";
    private static final int RSA_KEY_SIZE = 1024;
 
    public final static String UTF8 = "utf-8";
    private static Map<Integer, String> keyMap = new HashMap<Integer, String>();

    public static String formatString(String source) {
        if (source == null) {
            return null;
        }
        return source.replaceAll("\\r", "").replaceAll("\\n", "");
 
    }

    //用於封裝隨機產生的公鑰與私鑰
    public static void main(String[] args) throws Exception {
        //生成公鑰和私鑰
        genKeyPair();
        //加密字符串
        String message = "df723820";
        System.out.println("隨機生成的公鑰為:" + keyMap.get(0));
        System.out.println("隨機生成的私鑰為:" + keyMap.get(1));

        //公鑰加密、私鑰解密
        String messageEn = encrypt(message, keyMap.get(0));
        System.out.println(message + "公鑰加密後的字符串為:" + messageEn);
        String messageDe = decrypt(messageEn, keyMap.get(1));
        System.out.println("私鑰解密字符串為:" + messageDe);

        //私鑰加密、公鑰解密
        String enc = encryptByPrivateKey(message, keyMap.get(1));
        System.out.println(message + "私鑰加密後的字符串為:" + enc);
        String de = decryptByPublicKey(enc, keyMap.get(0));
        System.out.println("公鑰解密後的字符串:" + de);

    }

    /**
     * 隨機生成密鑰對
     *
     * @throws NoSuchAlgorithmException
     */
    public static void genKeyPair() throws NoSuchAlgorithmException {
        //KeyPairGenerator類用於生成公鑰和私鑰對，基於RSA算法生成對象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        //初始化密鑰對生成器，密鑰大小為96-1024位
        keyPairGen.initialize(RSA_KEY_SIZE, new SecureRandom());
        // 生成一個密鑰對，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        // 得到私鑰
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        // 得到公鑰
        String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
        // 得到私鑰字符串
        String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
        // 將公鑰和私鑰保存到Map
        keyMap.put(0, publicKeyString);// 0表示公鑰
        keyMap.put(1, privateKeyString);// 1表示私鑰
    }

    /**
     * RSA公鑰加密
     *
     * @param str       加密字符串
     * @param publicKey 公鑰
     * @return 密文
     * @throws Exception 加密過程中的異常信息
     */

    public static String encrypt(String str, String publicKey) throws Exception {
        publicKey = formatString(publicKey);
        //base64編碼的公鑰
        byte[] decoded = Base64.decodeBase64(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(KEY_ALGORITHM).generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes(UTF8)));
        return outStr;
    }

    /**
     * RSA私鑰解密
     *
     * @param str        加密字符串
     * @param privateKey 私鑰
     * @return 銘文
     * @throws Exception 解密過程中的異常信息
     */
    public static String decrypt(String str, String privateKey) throws Exception {
        privateKey = formatString(privateKey);
        //64位解碼加密後的字符串
        byte[] inputByte = Base64.decodeBase64(str.getBytes(UTF8));
        // base64編碼的私鑰
        byte[] decoded = Base64.decodeBase64(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(KEY_ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(decoded));
        // RSA解密
        Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }

    /**
     * 私鑰加密
     *
     * @param data       加密數據
     * @param privateKey 私鑰
     * @return
     */
    public static String encryptByPrivateKey(String data, String privateKey) {
        try {
            privateKey = formatString(privateKey);
            byte[] kb = Base64.decodeBase64(privateKey.getBytes(UTF8));
            PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(kb);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            PrivateKey key = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
            cipher.init(Cipher.ENCRYPT_MODE, key);
            byte[] b = data.getBytes(UTF8);
            byte[] encrypt = cipher.doFinal(b);
            return Base64.encodeBase64String(encrypt);
        } catch (Exception e) {
            logger.error("Failed to encryptByPrivateKey data.", e);
            throw new RuntimeException();
        }
    }

    /**
     * 公鑰解密
     *
     * @param data      解密數據
     * @param publicKey 公鑰
     * @return
     */
    public static String decryptByPublicKey(String data, String publicKey) {
        try {
            publicKey = formatString(publicKey);
            byte[] kb = Base64.decodeBase64(publicKey.getBytes(UTF8));
            X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(kb);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
            PublicKey key = keyFactory.generatePublic(x509EncodedKeySpec);
            Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
            //Cipher cipher = Cipher.getInstance(RSA_PADDING_KEY);
            cipher.init(Cipher.DECRYPT_MODE, key);
            byte[] b = data.getBytes(UTF8);
            byte[] decrypt = cipher.doFinal(Base64.decodeBase64(b));
            return new String(decrypt, UTF8);
        } catch (Exception e) {
            logger.error("Failed to decryptByPublicKey data.", e);
            throw new RuntimeException();
        }
    }
}

RSA公鑰加密-私鑰解密/私鑰加密-公鑰解密