关于java:RSA加密-Java

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简介
RSA 公开密钥明码体制是一种应用不同的加密密钥与解密密钥，“由已知加密密钥推导出解密密钥在计算上是不可行的”明码体制。
原理
依据数论，寻求两个大素数比较简单，而将它们的乘积进行因式分解却极其艰难，因而能够将乘积公开作为加密密钥，即公钥，而两个大素数组合成私钥。公钥是可公布的供任何人应用，私钥则为本人所有，供解密之用。
运算速度
因为进行的都是大数计算，使得 RSA 最快的状况也比 DES 慢上好几倍，无论是软件还是硬件实现。速度始终是 RSA 的缺点。一般来说只用于大量数据加密。RSA 的速度比对应同样安全级别的对称明码算法要慢 1000 倍左右。
其它链接
RSA 加密 – Vue
RSA 分段加密 – Java
RSA 分段解密 – Vue

实现类

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;

/**
 * @Description RSA 加密算法
 * @author coisini
 * @date Jul 5, 2021
 * @Version 1.0
 */
public class RSAUtil {

  private static final String ALGO = "RSA";
  private static final String CHARSET = "UTF-8";

  /**
   * 公钥 由 generateKeyPair()生成
   */
  private static final String PUBLIC_KEY = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCaaI4MBywkCjIppZnraqN3pbrcZTq/t0+aMBo8K3pK9BDD6XkM6N2Yfcva7BSFbUWuAcI7piXak0UKn9CElDuhNzUSgQn4IXKxIt3Iva5cV83qYumj+0yRjjLT8Muu1Y1rgBZjY9oBwhVoV+Twg25+UJ+6Q6HM4xTwQQJDoyy4jwIDAQAB";

  /**
   * 私钥 由 generateKeyPair()生成
   */
  private static final String PRIVATE_KEY = "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";

  /**
   * 生成密钥对
   * @throws NoSuchAlgorithmException
   */
  private static void generateKeyPair() throws NoSuchAlgorithmException {
      // KeyPairGenerator 类用于生成公钥和私钥对，基于 RSA 算法生成对象
      KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(ALGO);
      // 初始化密钥对生成器，密钥大小为 96-1024 位
      keyPairGen.initialize(1024, new SecureRandom());
      // 生成一个密钥对，保留在 keyPair 中
      KeyPair keyPair = keyPairGen.generateKeyPair();
      // 失去私钥
      RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
      // 失去公钥
      RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
      String publicKeyString = new String(Base64.getEncoder().encode(publicKey.getEncoded()));
      // 失去私钥字符串
      String privateKeyString = new String(Base64.getEncoder().encode((privateKey.getEncoded())));
      System.out.println(publicKeyString);
      System.out.println(privateKeyString);
  }

  /**
   * RSA 公钥加密
   * @param data 加密字符串
   * @return 密文
   * @throws Exception 加密过程中的异样信息
   */
  private static String encryptByPublicKey(String data) throws Exception {
      // base64 编码的公钥
      byte[] decoded = Base64.getDecoder().decode(PUBLIC_KEY);
      RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(ALGO).generatePublic(new X509EncodedKeySpec(decoded));
      // RSA 加密
      Cipher cipher = Cipher.getInstance(ALGO);
      // 公钥加密
      cipher.init(Cipher.ENCRYPT_MODE, pubKey);
      return Base64.getEncoder().encodeToString(cipher.doFinal(data.getBytes(CHARSET)));
  }

  /**
   * RSA 私钥解密
   * @param data 加密字符串
   * @return 明文
   * @throws Exception 解密过程中的异样信息
   */
  private static String decryptByPrivateKey(String data) throws Exception {byte[] inputByte = Base64.getDecoder().decode(data.getBytes(CHARSET));
      // base64 编码的私钥
      byte[] decoded = Base64.getDecoder().decode(PRIVATE_KEY);
      RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(ALGO).generatePrivate(new PKCS8EncodedKeySpec(decoded));
      // RSA 解密
      Cipher cipher = Cipher.getInstance(ALGO);
      // 私钥解密
      cipher.init(Cipher.DECRYPT_MODE, priKey);
      return new String(cipher.doFinal(inputByte));
  }

  /**
   * 私钥加密
   * 前端公钥解密
   * @param data 加密字符串
   * @return 密文
   * @throws Exception 加密过程中的异样信息
   */
  public static String encryptByPrivateKey(String data) throws Exception {
      // 获取私钥
      PrivateKey privateKey = getPrivateKey(PRIVATE_KEY);
      Cipher cipher = Cipher.getInstance("RSA");
      cipher.init(Cipher.ENCRYPT_MODE, privateKey);
      byte[] cipherText = cipher.doFinal(data.getBytes());
      String cipherStr = Base64.getEncoder().encodeToString(cipherText);
      return cipherStr;
  }

  /**
   * 公钥解密
   * @param data 解密字符串
   * @return 明文
   * @throws Exception 解密过程中的异样信息
   */
  public static String decryptByPublicKey(String data) throws Exception {
      // 获取公钥
      PublicKey publicKey = getPublicKey(PUBLIC_KEY);
      Cipher cipher = Cipher.getInstance("RSA");
      cipher.init(Cipher.DECRYPT_MODE, publicKey);
      byte[] cipherText = Base64.getDecoder().decode(data);
      byte[] decryptText = cipher.doFinal(cipherText);
      return new String(decryptText);
  }

  /**
   * 将 base64 编码后的私钥字符串转成 PrivateKey 实例
   * @param privateKey 私钥
   * @return PrivateKey 实例
   * @throws Exception 异样信息
   */
  private static PrivateKey getPrivateKey(String privateKey) throws Exception {byte[] keyBytes = Base64.getDecoder().decode(privateKey);
      PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
      KeyFactory keyFactory = KeyFactory.getInstance(ALGO);
      return keyFactory.generatePrivate(keySpec);
  }

  /**
   * 将 base64 编码后的公钥字符串转成 PublicKey 实例
   * @param publicKey 公钥
   * @return PublicKey 实例
   * @throws Exception 异样信息
   */
  private static PublicKey getPublicKey(String publicKey) throws Exception {byte[] keyBytes = Base64.getDecoder().decode(publicKey);
      X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
      KeyFactory keyFactory = KeyFactory.getInstance(ALGO);
      return keyFactory.generatePublic(keySpec);
  }


  public static void main(String[] args) {
      String data = "RSA encrypt!";
      try {// generateKeyPair();

          String encryDataByPublicKey = encryptByPublicKey(data);
          System.out.println("encryDataByPublicKey:" + encryDataByPublicKey);
          String decryDataByPrivateKey = decryptByPrivateKey(encryDataByPublicKey);
          System.out.println("decryDataByPrivateKey:" + decryDataByPrivateKey);

          String encryDataByPrivateKey = encryptByPrivateKey(data);
          System.out.println("encryDataByPrivateKey:" + encryDataByPrivateKey);
          String decryDataByPublicKey = decryptByPublicKey(encryDataByPrivateKey);
          System.out.println("decryDataByPublicKey:" + decryDataByPublicKey);
      } catch (Exception e) {e.printStackTrace();
      }
  }

}