java实用RSA的简单例子

绝地灬酷狼 2021-12-17 05:49 256阅读 0赞

import  java.io.BufferedReader;   
 import  java.io.BufferedWriter;  
 import  java.io.FileInputStream;   
 import  java.io.FileOutputStream;   
 import  java.io.IOException;  
 import  java.io.InputStreamReader;   
 import  java.io.ObjectInputStream;  
 import  java.io.ObjectOutputStream;   
 import  java.io.OutputStreamWriter;  
 import  java.math.BigInteger;  
 import  java.security.KeyPair;  
 import  java.security.KeyPairGenerator;  
 import  java.security.NoSuchAlgorithmException;  
 import  java.security.PrivateKey;  
 import  java.security.PublicKey;  
 import  java.security.SecureRandom;  
 import  java.security.interfaces.RSAPrivateKey;  
 import  java.security.interfaces.RSAPublicKey;  
  
 public   class  RSA  
\{  
     public   static   void  main(String\[\] args)  throws  NoSuchAlgorithmException, IOException, ClassNotFoundException  
    \{  
        KeyPair pair  =  generateKeyPair();  
        PrivateKey privateKey  =  pair.getPrivate();  
        PublicKey publicKey  =  pair.getPublic();  
  
         //  Save Pirvate Key   
         FileOutputStream f1  =   new  FileOutputStream( " private.ppk " );  
        ObjectOutputStream b1  =   new  ObjectOutputStream(f1);  
        b1.writeObject(privateKey);  
  
         //  Save Public Key   
         FileOutputStream f2  =   new  FileOutputStream( " public.ppk " );  
        ObjectOutputStream b2  =   new  ObjectOutputStream(f2);  
        b2.writeObject(publicKey);  
  
        encrypt();  
          
        decrypt();  
  
    \}  
  
     public   static   void  encrypt()  throws  IOException, ClassNotFoundException  
    \{  
        String msg  =   " Hello World! " ;  
  
        FileInputStream f  =   new  FileInputStream( " public.ppk " );  
        ObjectInputStream b  =   new  ObjectInputStream(f);  
        RSAPublicKey pbk  =  (RSAPublicKey) b.readObject();  
  
         //  RSA算法是使用整数进行加密的，在RSA公钥中包含有两个整数信息：e和n。对于明文数字m,计算密文的公式是m的e次方再与n求模。   
         BigInteger e  =  pbk.getPublicExponent();  
        BigInteger n  =  pbk.getModulus();  
  
         //  获取明文的大整数   
          byte  ptext\[\]  =  msg.getBytes( " utf-8 " );  
        BigInteger m  =   new  BigInteger(ptext);  
  
         //  加密明文   
         BigInteger c  =  m.modPow(e, n);  
          
         //  打印密文c   
         System.out.println( " c=  "   \+  c);  
          
         //  将密文以字符串形式保存在文件中   
         String cs  =  c.toString();  
        BufferedWriter out  =   new  BufferedWriter( new  OutputStreamWriter( new  FileOutputStream( " encrypt.dat " ),  " utf-8 " ));  
        out.write(cs,  0 , cs.length());  
        out.close();  
  
    \}  
  
     public   static   void  decrypt()  throws  IOException, ClassNotFoundException  
    \{  
        BufferedReader in  =   new  BufferedReader( new  InputStreamReader( new  FileInputStream( " encrypt.dat " ),  " utf-8 " ));  
        String ctext  =  in.readLine();  
        BigInteger c  =   new  BigInteger(ctext);  
          
         //  获取私钥   
         FileInputStream f  =   new  FileInputStream( " private.ppk " );  
        ObjectInputStream b  =   new  ObjectInputStream(f);  
        RSAPrivateKey prk  =  (RSAPrivateKey) b.readObject();  
          
         //  获取私钥的参数d,n   
         BigInteger d  =  prk.getPrivateExponent();  
        BigInteger n  =  prk.getModulus();  
              
         //  解密明文   
         BigInteger m  =  c.modPow(d, n);  
          
          
         //  计算明文对应的字符串并输出。   
          byte \[\] mt  =  m.toByteArray();  
        System.out.println( " PlainText is  "   \+   new  String(mt,  " utf-8 " ));  
          
    \}  
  
     public   static  KeyPair generateKeyPair()  throws  NoSuchAlgorithmException  
    \{  
        KeyPairGenerator keyPairGen  =  KeyPairGenerator.getInstance( " RSA " );  
         final   int  KEY\_SIZE  =   1024 ;  
        keyPairGen.initialize(KEY\_SIZE,  new  SecureRandom());  
        KeyPair keyPair  =  keyPairGen.genKeyPair();  
         return  keyPair;  
    \}  
  
\}

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转载于:https://www.cnblogs.com/hdjjun/archive/2011/06/28/2092761.html

[http_yanglingsx.blog.163.com_blog_static_90584353200910545647561]: http://yanglingsx.blog.163.com/blog/static/90584353200910545647561/