ch8_10.cs

《c#技术内幕代码》

using System;
using System.IO ;
using System.Security;
using System.Security.Cryptography;

public class StoreCryptoStream : ICryptoStream
{
    static byte[] tag1 = {(byte)'[',(byte)'S',(byte)'a',(byte)'u' ,(byte)'d' ,(byte)'e',(byte)'s' ,(byte)']'};
    static byte[] tag2=  {(byte)'[',(byte)'S',(byte)'a',(byte)'u' ,(byte)'r' ,(byte)'c',(byte)'2' ,(byte)']'};

    FileStream fs;
    
    public StoreCryptoStream(FileStream fout)
    {
    	fs=fout ;
    }
    
    public virtual void CloseStream() {fs.Close();}
    public virtual void CloseStream(Object obj) {fs.Close();}
    public virtual void SetSink(ICryptoStream pstm) {}
    public virtual void  SetSource(CryptographicObject co) {}
    public virtual ICryptoStream  GetSink () {return null;}
    
    public virtual void Write(byte[] bin)
    {
        int len = bin.GetLength(0);
        Write(bin, 0, len);
    }
    
    public virtual void Write(byte[] bin, int start, int len )
    {
        fs.Write(bin,start,len);
    }

}


public class CH8_10
{
    private byte[] symKey ;
    private byte[] symIV ;

    private bool GenerateKey(string password)
    {
        try
	{
           int i;
           int len;
           char[] cp = password.ToCharArray();
           len = cp.GetLength(0) ;
           byte[] bt = new byte[len];
	   
           for(i=0 ; i<len ;i++)
           {
               bt[i] =(byte) cp[i];
           }

           symKey=new byte[8] ;
           symIV = new byte[8] ;

           SHA1_CSP sha = new SHA1_CSP() ;
           sha.Write(bt) ;
           sha.CloseStream() ;
           for(i=0 ; i<8 ; i++)
           {
               symKey[i] = sha.Hash[i] ;
           }
           for(i=8 ; i<16 ; i++)
           {
               symIV[i-8]= sha.Hash[i] ;
           }

           return true;
       }
       
       catch(Exception e)
       {
           Console.WriteLine("A Exception Occured in Generating Keys :"+e.ToString()) ;
           return false ;
       }
    }
    
    private void DecryptData(string infile, string outfile)
    {
        try
	{
            FileStream fin = new FileStream(infile,FileMode.Open,FileAccess.Read);
            FileStream fout = new FileStream(outfile,FileMode.OpenOrCreate,FileAccess.Write);
            fout.SetLength(0) ;

            byte[] bin = new byte[4096] ;
            long totlen = fin.Length ;
            long rdlen=8;
            int len ;

            // Create the basic objects                
            SymmetricAlgorithm des = new DES_CSP() ;
	    
            // Create the stream.
            StoreCryptoStream scs = new StoreCryptoStream(fout);
            SymmetricStreamDecryptor ssd = des.CreateDecryptor(symKey, symIV);
	    
            ssd.SetSink(scs);
            scs.SetSource(ssd);
                        
            while (rdlen < totlen) 
	    {
                len = fin.Read(bin,0,4096);
                ssd.Write(bin,0,len);
                rdlen = rdlen + len;
            }
                        
            // Free up the resources
            ssd.CloseStream();
            fin.Close();
            fout.Close();
        }

        catch(Exception e)
        {
            Console.WriteLine("An exception occured while decrypting :" +e.ToString());
        }
    }
    
    public static void Main(string[] args)
    {
       CH8_10 app = new CH8_10();
       app.GenerateKey(args[0]);
       app.DecryptData( args[1], args[2] );
    }
}