java实现的基于RSA的公钥加密算法

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//非对称秘钥生成

import java.io.*;
import java.security.*;
import javax.crypto.*;
import javax.crypto.spec.*;

public class Skey_RSA
{
public static void main(String args[])throws Exception
  {
   KeyPairGenerator kpg=KeyPairGenerator.getInstance("RSA");
   kpg.initialize(1024);
   KeyPair kp=kpg.genKeyPair();
   PublicKey pbkey=kp.getPublic();
   PrivateKey prkey=kp.getPrivate();
   FileOutputStream f1=new FileOutputStream("Skey_RSA_pub.dat");
   ObjectOutputStream b1=new ObjectOutputStream(f1);
   b1.writeObject(pbkey);
   FileOutputStream f2=new FileOutputStream("Skey_RSA_priv.dat");
   ObjectOutputStream b2=new ObjectOutputStream(f2);
   b2.writeObject(prkey);
  }
}

//非对称加密

import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import javax.crypto.interfaces.*;
import java.security.interfaces.*;
import java.math.*;
import java.io.*;

public class Enc_RSA
{
public static void main (String args[])throws Exception{
  String s="Hello World!";
  FileInputStream f=new FileInputStream("Skey_RSA_pub.dat");
  ObjectInputStream b=new ObjectInputStream(f);
     RSAPublicKey pbk=(RSAPublicKey)b.readObject();
  BigInteger e=pbk.getPublicExponent();
  BigInteger n=pbk.getModulus();
  System.out.println("e="+e);
     System.out.println("n="+n);
  byte ptext[]=s.getBytes("UTF8");
  BigInteger m=new BigInteger(ptext);
  BigInteger c=m.modPow(e,n);
  System.out.println("c="+c);
  String cs=c.toString();
  BufferedWriter out=new BufferedWriter(new OutputStreamWriter(new FileOutputStream("Enc_RSA.dat")));
  out.write(cs,0,cs.length());
  out.close();
}
}

//非对称解密

public class Dec_RSA{
public static void main (String args[])throws Exception{
  BufferedReader in=new BufferedReader(new InputStreamReader(new FileInputStream("Enc_RSA.dat")));
  String ctext=in.readLine();
  BigInteger c=new BigInteger(ctext);

  FileInputStream f=new FileInputStream("Skey_RSA_priv.dat");
  ObjectInputStream b=new ObjectInputStream(f);
     RSAPrivateKey prk=(RSAPrivateKey)b.readObject();
  BigInteger d=prk.getPrivateExponent();
  BigInteger n=prk.getModulus();
  System.out.println("d="+d);
     System.out.println("n="+n);

  BigInteger m=c.modPow(d,n);
  System.out.println("m="+m);
  byte[] mt=m.toByteArray();
  System.out.println("PlainText is");
  for(int i=0;i<mt.length;i++)
  {
   System.out.print((char)mt[i]);
  }
}
}