package com.example.secret;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

import javax.crypto.Cipher;
import java.io.IOException;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 * RSA加密工具類
 *
 * @author sunziwen
 * 2018-07-31 20:27
 * @version 1.0
 **/
public class RSAUtil {
    /**
     * 獲取RSA公私鑰匙對
     * @return
     * @throws NoSuchAlgorithmException
     */
    public static KeyPair getKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
        keyPairGenerator.initialize(2048);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();
        return keyPair;
    }

    /**
     * 獲取公鑰(base64編碼)
     * @param keyPair
     * @return
     */
    public static String getPublicKey(KeyPair keyPair) {
        PublicKey publicKey = keyPair.getPublic();
        byte[] bytes = publicKey.getEncoded();
        return byte2Base64(bytes);
    }

    /**
     * 獲取私鑰(Base64編碼)
     * @param keyPair
     * @return
     */
    public static String getPrivateKey(KeyPair keyPair){
        PrivateKey privateKey = keyPair.getPrivate();
        byte[] bytes = privateKey.getEncoded();
        return byte2Base64(bytes);
    }

    /**
     * 將Base64編碼後的公鑰轉換成PublicKey物件
     * @param pubStr
     * @return
     * @throws Exception
     */
    public static PublicKey string2PublicKey(String pubStr) throws Exception{
        byte[] keyBytes = base642Byte(pubStr);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PublicKey publicKey = keyFactory.generatePublic(keySpec);
        return publicKey;
    }

    /**
     * 將Base64編碼後的私鑰轉換成PrivateKey物件
     * @param priStr
     * @return
     * @throws Exception
     */
    public static PrivateKey string2PrivateKey(String priStr) throws Exception{
        byte[] keyBytes = base642Byte(priStr);
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
        return privateKey;
    }

    /**
     * 公鑰加密
     * @param content
     * @param publicKey
     * @return
     * @throws Exception
     */
    public static byte[] publicEncrypt(byte[] content, PublicKey publicKey) throws Exception{
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] bytes = cipher.doFinal(content);
        return bytes;
    }

    /**
     * 私鑰解密
     * @param content
     * @param privateKey
     * @return
     * @throws Exception
     */
    public static byte[] privateDecrypt(byte[] content, PrivateKey privateKey) throws Exception{
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        byte[] bytes = cipher.doFinal(content);
        return bytes;
    }

    /**
     * 位元組陣列轉Base64編碼
     * @param bytes
     * @return
     */
    public static String byte2Base64(byte[] bytes){
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(bytes);
    }

    /**
     * Base64編碼轉陣列
     * @param base64Key
     * @return
     * @throws IOException
     */
    public static byte[] base642Byte(String base64Key) throws IOException {
        BASE64Decoder base64Decoder = new BASE64Decoder();
        return base64Decoder.decodeBuffer(base64Key);
    }
}
 

例項：

package com.example.secret;

import java.security.KeyPair;
import java.security.PrivateKey;
import java.security.PublicKey;
import org.junit.Test;


public class TestRSA {
    public static void main(String args[]) throws Exception {
        KeyPair keyPair = RSAUtil.getKeyPair();
        System.out.println("公鑰:");
        String publicKey = RSAUtil.getPublicKey(keyPair);
        System.out.println(publicKey);
        System.out.println("私鑰:");
        String privateKey = RSAUtil.getPrivateKey(keyPair);
        System.out.println(privateKey);
        String string = "勇敢行動才是我們面對生活的必然選擇";
        PublicKey publicKey1 = RSAUtil.string2PublicKey(publicKey);
        byte[] bytes = RSAUtil.publicEncrypt(string.getBytes(),publicKey1 );
        String msg = RSAUtil.byte2Base64(bytes);
        System.out.println("傳輸的加密後內容:");
        System.out.println(msg);
        byte[] bytes1 = RSAUtil.privateDecrypt(RSAUtil.base642Byte(msg), RSAUtil.string2PrivateKey(privateKey));
        System.out.println("解密後內容:");
        System.out.println(new String(bytes1));
    }

    @Test
    public void testRSA(){
        try {
            //===============生成公鑰和私鑰，公鑰傳給客戶端，私鑰服務端保留==================
            //生成RSA公鑰和私鑰，並Base64編碼
            KeyPair keyPair = RSAUtil.getKeyPair();
            String publicKeyStr = RSAUtil.getPublicKey(keyPair);
            String privateKeyStr = RSAUtil.getPrivateKey(keyPair);
            System.out.println("RSA公鑰Base64編碼:" + publicKeyStr);
            System.out.println("RSA私鑰Base64編碼:" + publicKeyStr);

            //=================客戶端=================
            //hello, i am infi, good night!加密
            String message = "hello, i am infi, good night!";
            //將Base64編碼後的公鑰轉換成PublicKey物件
            PublicKey publicKey = RSAUtil.string2PublicKey(publicKeyStr);
            //用公鑰加密
            byte[] publicEncrypt = RSAUtil.publicEncrypt(message.getBytes(), publicKey);
            //加密後的內容Base64編碼
            String byte2Base64 = RSAUtil.byte2Base64(publicEncrypt);
            System.out.println("公鑰加密並Base64編碼的結果：" + byte2Base64);


            //##############	網路上傳輸的內容有Base64編碼後的公鑰 和 Base64編碼後的公鑰加密的內容     #################



            //===================服務端================
            //將Base64編碼後的私鑰轉換成PrivateKey物件
            PrivateKey privateKey = RSAUtil.string2PrivateKey(privateKeyStr);
            //加密後的內容Base64解碼
            byte[] base642Byte = RSAUtil.base642Byte(byte2Base64);
            //用私鑰解密
            byte[] privateDecrypt = RSAUtil.privateDecrypt(base642Byte, privateKey);
            //解密後的明文
            System.out.println("解密後的明文: " + new String(privateDecrypt));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}