using System;
using System.IO;
using System.Security;
using System.Security.Cryptography;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;

namespace JavaScience {
public class SignFilehash{
 const int AT_KEYEXCHANGE = 1;  //keyspec values
 const int AT_SIGNATURE = 2;

 public static void Main()
	{
	const String ContainerName = "{EDEE793E-4FDB-47BC-A23A-EFC2A840E461}";
	int KeyType = AT_KEYEXCHANGE;
	String filename, sigfilename, rsapubparms, resp;
	FileStream fs = null;

	Console.Write("Enter name of file to sign: ");
	filename = Console.ReadLine();
	if(!File.Exists(filename)){
	 Console.WriteLine("File {0} not found. ", filename);
	 return;
	 }
	byte[] data1ToHash = SignFilehash.GetFileBytes(filename);
	Console.WriteLine("File has {0} bytes", data1ToHash.Length);
	SHA1Managed SHhash = new SHA1Managed();
	// --- compute SHA-1 hash of ASCII file bytes
	byte[] hashvalue = SHhash.ComputeHash(data1ToHash);
	Console.WriteLine("\nSHA1 hash of file {0} ({1} bytes):\n{2}", filename, hashvalue.Length, BitConverter.ToString(hashvalue));
	// --- compute the encrypted hash (RSA PKCS #1 version 1.5 signature)  -----
	byte[] sigvalue = SignFilehash.GetSignature(hashvalue, ContainerName, KeyType);
	if(sigvalue ==null){
	 Console.WriteLine("Couldn't get signature");
	 return;
	}
 	Console.WriteLine("\nSigned Hash of file {0} ({1} bytes):\n{2}", filename, sigvalue.Length, BitConverter.ToString(sigvalue));

 //------ Write signature to output file ---------------
	Console.Write("\nWrite encrypted hash (signature) to file? ");
	resp = Console.ReadLine();
	if(resp.Equals("y") || resp.Equals("y") ||resp.Equals("yes") ||resp.Equals("YES")){
	 Console.Write("Enter name of output signature file: ");
	 sigfilename = Console.ReadLine();
	  if (File.Exists(sigfilename)) {
           Console.WriteLine("File '{0}' already exists!", sigfilename);
           return;
	  }	 
	try{
	 fs = new FileStream(sigfilename, FileMode.CreateNew);
	 fs.Write(sigvalue, 0, sigvalue.Length);
	 Console.WriteLine("\nWrote signature file '{0}'", sigfilename) ;
	}
	catch(Exception e) {
	 Console.WriteLine(e.Message) ; 
	}
	finally {
	 fs.Close();
	}
      }

 //------ Serialize RSAParams to store public key info. ---------------
	Console.Write("\nWrite public key information to file? ");
	resp = Console.ReadLine();
	if(resp.Equals("y") || resp.Equals("y") ||resp.Equals("yes") ||resp.Equals("YES")){
	 Console.Write("Enter name of output PUBLIC KEY (serialized RSAParams) file: ");
	 rsapubparms = Console.ReadLine();
	  if (File.Exists(rsapubparms)) {
           Console.WriteLine("File '{0}' already exists!", rsapubparms);
           return;
	  }	 
        CspParameters cp = new CspParameters();
        cp.KeyContainerName = ContainerName;
	cp.KeyNumber = KeyType;
	RSACryptoServiceProvider rsaCSP = new RSACryptoServiceProvider(cp);
       	RSAParameters rsaParams = rsaCSP.ExportParameters(false); //only export public part

 Console.WriteLine("\nModulus\n {0}", BitConverter.ToString(rsaParams.Modulus));
 Console.WriteLine("\nExponent\n {0}", BitConverter.ToString(rsaParams.Exponent));



	fs = new FileStream(rsapubparms, FileMode.CreateNew);
	BinaryFormatter formatter = new BinaryFormatter();
        try 
        {
	 formatter.Serialize(fs, rsaParams);
	 Console.WriteLine("\nWrote RSAParameters file '{0}'", rsapubparms) ;
        }
        catch (SerializationException e) 
        {
            Console.WriteLine("Failed to serialize:  " + e.Message);
        }
	catch (Exception e) {
	 Console.WriteLine(e.Message) ;
	}
        finally 
        {
            fs.Close();
        }
    }

  }


 private static byte[] GetFileBytes(String filename){
	if(!File.Exists(filename))
	 return null;
	Stream stream=new FileStream(filename,FileMode.Open);
	int datalen = (int)stream.Length;
	byte[] filebytes =new byte[datalen];
	stream.Seek(0,SeekOrigin.Begin);
	stream.Read(filebytes,0,datalen);
	stream.Close();
	return filebytes;
  }


 private static byte[] GetSignature(byte[] HashValue, String ContainerName, int keyspec) {
  //--- automatically creates CrypoAPI key container with ContainerName and keyspec if doesn't already exist
        CspParameters cp = new CspParameters();
        cp.KeyContainerName = ContainerName;
	cp.KeyNumber = keyspec;
  if(HashValue == null || HashValue.Length==0)
	return null;
	byte[] SignedHash=null;
	try{
	RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(cp);
	RSAPKCS1SignatureFormatter RSAFormatter = new RSAPKCS1SignatureFormatter(RSA);
	RSAFormatter.SetHashAlgorithm("SHA1");
	SignedHash = RSAFormatter.CreateSignature(HashValue);
	}
	catch(CryptographicException e){
		Console.WriteLine(e.Message) ;
	}
  return SignedHash;
  }
 }
}