Example of how to implement asymmetric encryption using RSA in Java

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java Examples of implementing asymmetric encryption using RSA

Popular understanding of RSA:

You just need to think about it: since it is encryption, you definitely don’t want others to Knowing my message, only I can decrypt it, so it can be concluded that the public key is responsible for encryption and the private key is responsible for decryption. Similarly, since it is a signature, I definitely don’t want someone to pretend to be me and send a message. Only I can publish this signature. Therefore, it can be concluded that the private key is responsible for signing and the public key is responsible for verification.

Implementation code:

package com.sahadev; 
 
import java.security.KeyFactory; 
import java.security.KeyPair; 
import java.security.KeyPairGenerator; 
import java.security.PrivateKey; 
import java.security.PublicKey; 
import java.security.interfaces.RSAPrivateKey; 
import java.security.interfaces.RSAPublicKey; 
import java.security.spec.PKCS8EncodedKeySpec; 
import java.security.spec.X509EncodedKeySpec; 

import javax.crypto.Cipher; 
import org.apache.commons.codec.binary.Base64; 

public class RSA { 
public static void main(String[] args) { 
    JDKRSA(); 
  } 
 
  public static void JDKRSA() { 
    try { 
      // 构建密钥对儿 
      KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA"); 
      keyPairGenerator.initialize(512); 
      KeyPair keyPair = keyPairGenerator.generateKeyPair(); 
      RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic(); 
      RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate(); 
      System.out.println("Public Key : " + org.apache.commons.codec.binary.Base64.encodeBase64String(rsaPublicKey.getEncoded())); 
      System.out.println("Private Key : " + org.apache.commons.codec.binary.Base64.encodeBase64String(rsaPrivateKey.getEncoded())); 
 
      // 2.私钥加密，公钥解密---加密 
      PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded()); 
      KeyFactory keyFactory = KeyFactory.getInstance("RSA"); 
      PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec); 
      Cipher cipher = Cipher.getInstance("RSA"); 
      cipher.init(Cipher.ENCRYPT_MODE, privateKey); 
      byte[] result = cipher.doFinal(DH.src.getBytes()); 
      System.out.println("私钥加密，公钥解密------加密 : " + Base64.encodeBase64String(result)); 
 
      // 3.私钥加密，公钥解密---解密 
      X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded()); 
      keyFactory = KeyFactory.getInstance("RSA"); 
      PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec); 
      cipher = Cipher.getInstance("RSA"); 
      cipher.init(Cipher.DECRYPT_MODE, publicKey); 
      result = cipher.doFinal(result); 
      System.out.println("私钥加密，公钥解密------解密 : " + new String(result)); 
 
      // 4.公钥加密，私钥解密---加密 
      x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded()); 
      keyFactory = KeyFactory.getInstance("RSA"); 
      publicKey = keyFactory.generatePublic(x509EncodedKeySpec); 
      cipher = Cipher.getInstance("RSA"); 
      cipher.init(Cipher.ENCRYPT_MODE, publicKey); 
      result = cipher.doFinal(DH.src.getBytes()); 
 
      System.out.println("公钥加密，私钥解密------加密 : " + Base64.encodeBase64String(result)); 
 
      // 5.公钥加密，私钥解密---解密 
      pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded()); 
      keyFactory = KeyFactory.getInstance("RSA"); 
      privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec); 
      cipher = Cipher.getInstance("RSA"); 
      cipher.init(Cipher.DECRYPT_MODE, privateKey); 
      result = cipher.doFinal(result); 
      System.out.println("公钥加密，私钥解密------解密 : " + new String(result)); 
    } catch (Exception e) { 
      e.printStackTrace(); 
    } 
  } 
}

Attached is the output result:

Public Key : MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAJcFshoP5xm94r2aTbe++aMZMzJtXHxDpqmMQ9aL1cEthr2Xtac+Eckv32Kzb4R8C/6vObNBfd8sWx9FU5N2y6cCAwEAAQ== 
Private Key : MIIBVAIBADANBgkqhkiG9w0BAQEFAASCAT4wggE6AgEAAkEAlwWyGg/nGb3ivZpNt775oxkzMm1cfEOmqYxD1ovVwS2GvZe1pz4RyS/fYrNvhHwL/q85s0F93yxbH0VTk3bLpwIDAQABAkBdAA7rabug6IRGykztyFcmjxAuD5aSl358jnoAFuCtMo4skfxh1vR4ENFUE0Lt0zJ3CKVH0o9UQDNG0r4jeOGRAiEA3KuXps9OG0AXuxLggg0e7B1Os5C3gNrH2fMqAPjtpY0CIQCvM4EPfdrjjNQiM0ATVBT5jZnw3PRu33pdyISWuoMHAwIgDOLMSUZjxj2Y5Si2CYIgoyMW/G9f99tOvlBvzHy8y+UCIF94MVu/uQdGNlJsmv3tU4CpKLmXrZq9LHDuU1HPUJcBAiEAy/0OS2Q9EBfmPwhsGXF4WMxj4wG0xzNFWxSeZB0qxzk= 
私钥加密，公钥解密------加密 : NXF87irBEmK3x/fW7IWY4GuA8AP4Rvj4DJSp2Cjjsoo5X/ScHHKdvYtlM+9TOUAvMeuKWk5WH70g53q7+E73zg== 
私钥加密，公钥解密------解密 : Hello,sahadev! 
公钥加密，私钥解密------加密 : hjL8928jCbNtVCRhKaYAxQNJmiIAktBskhff2I01pbaHtfGH6GJTcP1i345/3I9OzwoVFxvi/oXgVJsIsg7MOQ== 
公钥加密，私钥解密------解密 : Hello,sahadev!

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