RSA暗号化方式と復号方式の実現方法（推奨）

package com.mstf.rsa;
 
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 com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
 
/*RSA    。    ，  ，        。
RSA       
RSA            ，            （  100     ）   。
   ，                             
     ： 
 1.        p,q ,   n=p*q; 
 2.         e ,   e   (p-1)*(q-1)   
 3.   Euclid          d ,      e*d = 1(mod(p-1)*(q-1)) (   n,d     ) 
 4:        (n,e)     (n,d) 
 RSA   
 *            ，  RSA       DES  100 ，            。 
 *      RSA   。              。*/
public class RSAsecurity {
 
 public static String src = "admin";
 
 public void priENpubDE() {
 
  try {
   //      
   KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
   //     
   keyPairGenerator.initialize(1024);
   //       
   KeyPair keyPair = keyPairGenerator.generateKeyPair();
   //   
   RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
   //   
   RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();
 
   // 2.    ，    ----  
   //     
   PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
   KeyFactory keyFactory = KeyFactory.getInstance("RSA");
   PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
   // Cipher             ，  getinstance     
   Cipher cipher = Cipher.getInstance("RSA");
   //      
   cipher.init(Cipher.ENCRYPT_MODE, privateKey);
   byte[] result = cipher.doFinal(src.getBytes());
   System.out.println("    ，    ----  :" + Base64.encode(result));
 
   // 3.    ，    ----  
   //     
   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("    ，    ----  :" + new String(result));
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 
 }
 
 public void pubENpriDE() {
  try {
   // 1.     
   KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
   //     
   keyPairGenerator.initialize(512);
   //       
   KeyPair keyPair = keyPairGenerator.generateKeyPair();
   //   
   RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic();
   //   
   RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate();
 
   // 2.    ，    ----  
   X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
   KeyFactory keyFactory = KeyFactory.getInstance("RSA");
   PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
   //      
   // Cipher             ，  getinstance     
   Cipher cipher = Cipher.getInstance("RSA");
   cipher.init(Cipher.ENCRYPT_MODE, publicKey);
   //      
   byte[] result = cipher.doFinal(src.getBytes());
   System.out.println("    ，    ----  :" + Base64.encode(result));
 
   // 3.    ，    -----  
   PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
   keyFactory = KeyFactory.getInstance("RSA");
   PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
   //      
   cipher.init(Cipher.DECRYPT_MODE, privateKey);
   //      
   result = cipher.doFinal(result);
   System.out.println("    ，    -----  :" + new String(result));
 
  } catch (Exception e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
 
 }
}

package com.mstf.rsa;
 
import com.mstf.rsa.RSAsecurity;
 
public class RSAtest {
 public static void main(String[] args) {
  RSAsecurity rsAsecurity = new RSAsecurity();
  System.out.println("         ：");
  rsAsecurity.priENpubDE();
  System.out.println("         ：");
  rsAsecurity.pubENpriDE();
 }
}