dec_rsa.java

java程序实现的RSA算法

/*
m:明文;
c:密文;
p,q:两个大素数
n=p*q;FI(n)=(p-1)(q-1);
加密密钥(私钥):e;
解密密钥(公钥):d;
d*e=1 mod FI(n)
加密过程:
c=m^e(mod n);
解密过程:
m=c^d(mod n);
*/

//加密过程

//引入相关头文件,主要是java.security包下的类和java.crpto下的类

import java.security.interfaces.*;
import java.math.*;
import java.io.*;


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

    FileInputStream f=new FileInputStream("Skey_RSA_priv.txt");
    ObjectInputStream b=new ObjectInputStream(f);
    RSAPrivateKey prk=(RSAPrivateKey)b.readObject( );
    BigInteger d=prk.getPrivateExponent();
    BigInteger n=prk.getModulus();
	
    //BigInteger n = new BigInteger("65531".getBytes());//打算用自己的私钥
	//BigInteger d = new BigInteger("21905".getBytes());
    
    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();
    String test = new String(mt);
    System.out.println("PlainText is " + test);
    //////for(int i=0;i<mt.length;i++){
     ////   System.out.print(mt.toString());
    //}

    
  }
}