关于java:RSA分段加密-Java

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RSA 的 key 长度为 1024 用公钥加密比拟长的字符串时会异样，这里介绍 java 如何对长文本进行分段加密，附上其它链接
RSA 加密 – Java
RSA 加密 – Vue
RSA 分段解密 – Vue

实现类

import com.alibaba.fastjson.JSONObject;
import org.apache.commons.lang3.ArrayUtils;
import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.EncodedKeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;

public class RSAUtils {

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

  /**
   * 私钥
   */
  private static final String PRIVATE_KEY = "MIICdgIBADANBgkqhkiG9w0BAQEFAASCAmAwggJcAgEAAoGBAJpojgwHLCQKMimlmetqo3elutxlOr+3T5owGjwrekr0EMPpeQzo3Zh9y9rsFIVtRa4BwjumJdqTRQqf0ISUO6E3NRKBCfghcrEi3ci9rlxXzepi6aP7TJGOMtPwy67VjWuAFmNj2gHCFWhX5PCDbn5Qn7pDoczjFPBBAkOjLLiPAgMBAAECgYBnBBKhG7frY5IMDxwd4Euna767hB4qAlbte+JE+ozgrOzyiDXm0wXk0yjKqm8WhczTRwEbYsImjdKmP/GSQoN1AU7yEzM8j0Jgq46m9ZVrHhu2NpuZpr+XueWnA6FNz6tybBgcCwA4t8dvfbOrvjqhrCu01O1xWIpjronyFBN4IQJBAPGuF58xjXyANnp5YU8NhUQ73tTIveRlOpMXDSYkf9lWG26XIGUIsTe0f5jssiNmYtxG+lUm9LLfZgOLcrVkDZ0CQQCjjrBNMXub49efVTCg+nCGT2QXW2BHg/qs5vu8Y34LUHoD/hoEJ+AOWOdnhpRoYOpBwJAm3Gu4a1VmZGGafp0bAkAdfY3aWhSWtZpwNXF/UPoLCnc1Zc1uGkAchLqRBfEn1w7/3qcQTRA66OaNBYzzLuIvWOXhECDZ1tK+6fw0UCItAkAOLibW6n1fDKf7JnWq30u2OVfiNofoa2bmarhUowOgk3+grP0wcwyX8dlOPnrLeeuVe86DsASe3p9u2zEjJesVAkEAhkLiv4TXrC1QlJl7ghksUfFmdT7M4Zxlzj10ConMgq68HkLdmn2nNLsjhUHGwJe3EqM6aozn4zw/Z7uPIT9Fsw==";

  /**
   * 私钥分段加密
   * @param content
   * @return
   * @throws Exception
   */
  public static String encryptLongByPrivateKey(String content) throws Exception {
      // 获取私钥
      PrivateKey privateKey = getPrivateKey(PRIVATE_KEY);
      Cipher cipher = Cipher.getInstance("RSA");
      cipher.init(Cipher.ENCRYPT_MODE, privateKey);

      // URLEncoder 编码解决中文乱码问题
      byte[] data = URLEncoder.encode(content, "UTF-8").getBytes("UTF-8");
      // 加密时超过 117 字节就报错。为此采纳分段加密的方法来加密
      byte[] enBytes = null;
      for (int i = 0; i < data.length; i += 117) {
          // 留神要应用 2 的倍数，否则会呈现加密后的内容再解密时为乱码
          byte[] doFinal = cipher.doFinal(ArrayUtils.subarray(data, i, i + 117));
          enBytes = ArrayUtils.addAll(enBytes, doFinal);
      }
      return Base64.getEncoder().encodeToString(enBytes);
  }

  /**
   * 公钥分段解密
   * @param content
   * @return
   * @throws Exception
   */
  public static String decryptLongByPublicKey(String content) throws Exception {
      // 获取公钥
      PublicKey publicKey = getPublicKey(PUBLIC_KEY);
      Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
      cipher.init(Cipher.DECRYPT_MODE, publicKey);
      byte[] data =  Base64.getDecoder().decode(content);

      // 返回 UTF- 8 编码的解密信息
      int inputLen = data.length;
      ByteArrayOutputStream out = new ByteArrayOutputStream();
      int offSet = 0;
      byte[] cache;
      int i = 0;
      // 对数据分段解密
      while (inputLen - offSet > 0) {if (inputLen - offSet > 128) {cache = cipher.doFinal(data, offSet, 128);
          } else {cache = cipher.doFinal(data, offSet, inputLen - offSet);
          }
          out.write(cache, 0, cache.length);
          i++;
          offSet = i * 128;
      }
      byte[] decryptedData = out.toByteArray();
      out.close();
      return URLDecoder.decode(new String(decryptedData, "UTF-8"));
  }

  /**
   * 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
   */
  public static PublicKey getPublicKey(String publicKey) throws Exception {EncodedKeySpec keySpec = new X509EncodedKeySpec(Base64.getDecoder().decode(publicKey));
      KeyFactory keyFactory = KeyFactory.getInstance("RSA");
      return keyFactory.generatePublic(keySpec);
  }

  /**
   * 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("RSA");
      return keyFactory.generatePrivate(keySpec);
  }

  public static void main(String[] args) throws Exception {Map<String,Object> map = new HashMap<>();
      map.put("name", "Cosini");
      map.put("phone", "13888888888");
      String content = JSONObject.toJSONString(map);

      // 密文
      String cipherText = RSAUtils.encryptLongByPrivateKey(content);
      System.out.println("cipherText:" + cipherText);

      // 明文
      String plainText = RSAUtils.decryptLongByPublicKey(cipherText);
      System.out.println("plainText:" + plainText);
  }

}