2012

IT352 : Network Security | Najwa AlGhamdi

[MINI PROJECT 1] Instructions about mini-project1 programming assignments

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Programming environment

1. Programming language : C#.net

2. Programming environment: Visual Studio.net, you can download an express version

of c# from here.

Part 1 – Encryption

Project Setup

Go to File>New>Project. The following dialog box will appear.

Select “Console Application” template. Name the project part_Encryption. Place the file

ciphertext.dat and key.dat in your project folder>bin>debug.

Code

In “program.cs” header add using System.Security.Cryptography;

using System.IO;

add the following functions befor main.

IT 352 :Network Security

2nd Semester 1432/33 H

Mini Project1 : Encryption

Due:Fri, 2 March @ Midnight

King Saud University

College of Computer and Information Sciences

Department of Information Technology

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static string decrypt ( byte[] key , byte[] data)

{

// write the decryption code here

}

Use this function to read data

static byte[] read_data( string filename)

{

Byte[] bytes;

FileStream stream = new FileStream(filename, FileMode.Open,

FileAccess.Read);

BinaryReader br = new BinaryReader(stream);

//read the stream

bytes = br.ReadBytes( Convert.ToInt16 (stream.Length));

//store data in array of bytes

br.Close();

stream.Close();

return bytes;

}

in “program.cs” static void Main(string[] args) add

string cipherfile= "";

string key_file = "" ;

string output = "" ;

// read input from console

cipherfile = args[0];

key_file = args[1];

output = args[2];

// read data and key from file

byte[] data= read_data(cipherfile);

byte[] key = read_data(key_file);

// write output in file

StreamWriter writer =new StreamWriter(output);

writer.WriteLine(decrypt(key, data);

writer.Close();

To view the output, go to your project folder >bin>debug, copy all files there in a folder

named “EXE-FILE” . Then open the command line prompt window and do as it shown in the

figure below.

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I placed the EXE-FILE folder under the D to easy access it. Now, open EXE-FILE folder, you should find

a text file called “output” containing the decrypted message.

Part2- Brute Force

Project Setup

Go to File>New>Project. The following dialog box will appear.

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Select “Console Application” template. Name the project “findk”. Place the file ciphertext2.dat

and partial_key.dat in your project folder>bin>debug.

Code

In “program.cs” header add using System.Security.Cryptography;

using System.IO;

add the following functions befor main.

static string decrypt ( byte[] key , byte[] data)

{

// use the same decryption function in part1

}

Use this function to read data

static byte[] read_data( string filename)

{

Byte[] bytes;

FileStream stream = new FileStream(filename, FileMode.Open,

FileAccess.Read);

BinaryReader br = new BinaryReader(stream);

//read the stream

bytes = br.ReadBytes( Convert.ToInt16 (stream.Length));

//store data in array of bytes

br.Close();

stream.Close();

return bytes;

}

static string findkey(byte[] cipher_text, byte[]partial_key)

{

//write your brute force function here

}

use this function for output

static void print_resaults(string resault , byte[] key)

{ //' function objective : to print the decrypted message , the missing

bytes and the time spend in searching process

//' parametter : resault that hold the decrypted message

//' key that hold the decryption key

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string hex ;

byte[] missingbytes = {0,0,0,0} ;

Array.Copy (key, 12, missingbytes, 0, 4);

Console.WriteLine(" The message = " + resault);

span = date2.Subtract(date1);

//' convert the missing bytes to hex

hex = System.BitConverter.ToString(missingbytes, 0, 4);

Console.WriteLine("The key = " + System.BitConverter.ToString(key, 0,

16));

Console.WriteLine(" The missing bytes in hex = " + hex);

// print the time spent

Console.WriteLine(" press any key to continue ");

Console.Read();

}

in “program.cs” static void Main(string[] args) add

string cipherfile = "";

string partial_key_file = "";

string plain_text ;

cipherfile = args[0];

partial_key_file = args[1];

byte[] data= read_data(cipherfile);

byte[] partial_key = read_data(partial_key_file);

byte[] fullkey = {0,0,0,0, 0,0,0,0 ,0,0,0,0, 0,0,0,0};

System.Array.Copy(partial_key, 0, fullkey, 0, 12);

plain_text = findkey(data, fullkey);

print_resaults(plain_text, fullkey);

To view the output, go to your project folder >bin>debug, copy all files there in the folder

“EXE-FILE” . Then open the command line prompt window and do as it shown in the figure

below.

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What to submit A zipped folder contains the following

1. EXE-FILE : contains the two-parts’ EXE files.

2. Source-code : contains the two projects.

3. Report: tell your story in how did decrypt and implement the brute force with screen shots of

the results.