Java实现RSA生成密钥并加解密

问题描述

需要对密码需要进行加密处理，使用RSA加解密对密码进行加密，对过程进行一下记录。

生成公钥和私钥

例子是通过公钥加密，私钥解密。这里后端同时进行了公钥加密，然后也进行了私钥解密，实际使用场景应该是前端加密后端解密，将公钥直接放在H5，APP等前端程序中，即使被拿到，想要用公钥破解出私钥也是极难的。公钥提供给前端，私钥放在服务端。通过RSA公钥加密明文，加密后的密文发到服务端，服务端用RSA私钥解密得出明文

步骤

① RSA工具类

package com.changkong.util;

import java.nio.charset.StandardCharsets;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import org.apache.commons.codec.binary.Base64;


public class RSAUtil {
    private static Map keyMap = new HashMap<>(); // 用于封装随机产生的公钥与私钥

    public static void main(String[] args) {
        //生成公钥和私钥
        genKeyPair();
        //加密字符串
        String message = "df723820";
        System.out.println("随机生成的公钥为:" + keyMap.get(0));
        System.out.println("随机生成的私钥为:" + keyMap.get(1));
        String messageEn = encrypt(message, keyMap.get(0));
        System.out.println("加密后的字符串为:" + messageEn);
        String messageDe = decrypt(messageEn, keyMap.get(1));
        System.out.println("还原后的字符串为:" + messageDe);
    }

    //随机生成密钥对
    public static void genKeyPair() {
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = null;

        try {
            keyPairGen = KeyPairGenerator.getInstance("RSA");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }

        // 初始化密钥对生成器，密钥大小为96-1024位
        assert keyPairGen != null;
        keyPairGen.initialize(1024, new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();   // 得到私钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  // 得到公钥
        String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
        // 得到私钥字符串
        String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
        // 将公钥和私钥保存到Map
        keyMap.put(0, publicKeyString);  //0表示公钥
        keyMap.put(1, privateKeyString);  //1表示私钥
    }

    /**
     * RSA公钥加密
     *
     * @param str       加密字符串
     * @param publicKey 公钥
     * @return 密文
     */
    public static String encrypt(String str, String publicKey) {
        //base64编码的公钥
        byte[] decoded = Base64.decodeBase64(publicKey);
        RSAPublicKey pubKey = null;
        String outStr = null;
        try {
            pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
            Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-1AndMGF1Padding");
            cipher.init(Cipher.ENCRYPT_MODE, pubKey);
            outStr = Base64.encodeBase64String(cipher.doFinal(str.getBytes(StandardCharsets.UTF_8)));
        } catch (InvalidKeySpecException | BadPaddingException | IllegalBlockSizeException | InvalidKeyException |
                NoSuchPaddingException | NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        //RSA加密
        return outStr;
    }


    /**
     * RSA私钥解密
     *
     * @param str        加密字符串
     * @param privateKey 私钥
     * @return 明文
     */
    public static String decrypt(String str, String privateKey) {
        //64位解码加密后的字符串
        byte[] inputByte = Base64.decodeBase64(str.getBytes(StandardCharsets.UTF_8));
        //base64编码的私钥
        byte[] decoded = Base64.decodeBase64(privateKey);
        RSAPrivateKey priKey = null;
        //RSA解密
        Cipher cipher = null;
        String outStr = null;
        try {
            priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
            cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-1AndMGF1Padding");
            cipher.init(Cipher.DECRYPT_MODE, priKey);
            outStr = new String(cipher.doFinal(inputByte));
        } catch (InvalidKeySpecException | NoSuchAlgorithmException | NoSuchPaddingException | BadPaddingException |
                IllegalBlockSizeException | InvalidKeyException e) {
            e.printStackTrace();
        }
        return outStr;
    }
}