c#

Collage Generator

I needed to find images of money. I searched the Internet but couldn’t find anything that great or multiple images that were unique but in the same style. I decided to download images of bills from Wikipedia and write my own program to generate a few different collages. Below I’ve included some screen shots of example usages and their corresponding output. Scroll to the bottom of this post to download the program.

Collage Generator v1.0.0 Copyright (c) 2011 Tanner Jepsen

Friday, April 8th, 2011 algorithms, c#, coding, computers 1 Comment

Identify This Cipher

Using cryptographic analysis on a cipher produced by an existing software program, I was able to write my own compatible algorithm for re-producing the cipher. The only trouble is I have no idea which cipher it is. Perhaps combinations of different ciphers or maybe even a new cipher all together? No, I won’t say which software program uses this cipher, but I wonder if anyone can identify and/or classify it. I believe it to be a symmetric key stream cipher–albeit, very weak and very easy to analyze.

Disclaimer: I invoke my right to free speech to post cryptographic source code. See Bernstein v. United States.

Usage Examples:

Console.WriteLine(Convert.ToBase64String("mypassword".Cipher("378518030611953")));
// or
Console.WriteLine("mypassword".Cipher("378518030611953").ToHexString());
// or
Console.WriteLine("mypassword".Cipher(ASCIIEncoding.ASCII.GetBytes("somekey")).ToHexString());

Corresponding Output Examples:

// y8kJikhp6ItISg==
// or
// cbc9098a4869e88b484a
// or
// c5c4a58605c4c785a527

The Code:

using System;
using System.Text;

namespace MyExtensions
{
    public static class Extensions
    {
        public static byte[] Cipher(this string password, string key)
        {
            byte[] cipher = System.Text.ASCIIEncoding.ASCII.GetBytes(password);
            return cipher.Cipher(key);
        }

        public static byte[] Cipher(this string password, byte[] key)
        {
            byte[] cipher = System.Text.ASCIIEncoding.ASCII.GetBytes(password);
            return cipher.Cipher(key);
        }

        public static byte[] Cipher(this byte[] password, string key)
        {
            try
            {
                byte[] k = key.ParseBytes();
                return password.Cipher(k);
            }
            catch (Exception e)
            {
                throw new Exception("The key can consist only of a string of numbers. No letters or special characters.", e);
            }
        }

        public static byte[] Cipher(this byte[] password, byte[] key)
        {
            byte[] cipher = password;
            for (int i = 0; i < cipher.Length; i++)
            {
                int first = 0x09;
                int last = 0xE9;
                int rounds = cipher[i] ^ key[i % key.Length];

                for (int y = 0; y <= rounds; y++)
                {
                    last += 32;
                    if (last > 255) last = first = first + (y % 16 / 2) - 3;
                    if (last < 0) last = first = 14;
                }
                cipher[i] = (byte)last;
            }
            return cipher;
        }

        public static byte[] ParseBytes(this string s)
        {
            return s.ToCharArray().ParseBytes();
        }

        public static byte[] ParseBytes(this char[] data)
        {
            byte[] p = new byte[data.Length];
            for (int i = 0; i < data.Length; i++)
            {
                byte parsed;
                if (!byte.TryParse(data[i].ToString(), out parsed))
                    throw new Exception("The input can only consist of numbers. No letters or special characters.");
                p[i] = parsed;
            }
            return p;
        }

        public static string ToHexString(this byte[] data)
        {
            string s = string.Empty;
            for (int i = 0; i < data.Length; i++)
            {
                s += data[i].ToHexString();
            }
            return s;
        }

        public static string ToHexString(this byte b)
        {
            return Convert.ToString(b, 16).PadLeft(2, "0");
        }

        public static string PadLeft(this string s, int totalWidth, string padding)
        {
            return s.PadLeft(totalWidth, char.Parse(padding));
        }

        public static string PadRight(this string s, int totalWidth, string padding)
        {
            return s.PadRight(totalWidth, char.Parse(padding));
        }
    }
}
Saturday, March 12th, 2011 academic, algorithms, c#, coding, computers, data No Comments