Railfence cipher encoder

• Download source code + tester - 21.1 KB

Introduction

The rail fence cipher is where you have some text like joejoe and you split it on two lines like:

j e o
o j e

Now you combine the two lines and get: jeooje

Encoding

At school, I have been taught how to encode stuff into the rail fence cipher. Here's how:

/// <summary>
/// Encodes stuff
/// </summary>
/// <param name="input">The string to encode</param>
/// <returns>Encoding result</returns>
public static string Encode(string input)
{
    char[] inputc = input.ToCharArray();
    string pasA = "";
    string pasB = "";
    bool x = true;
    foreach(char ch in inputc)
    {
        if(x == true)
        {
            pasA += ch;
            x = false;
        }
        else
        {
            x = true;
            pasB += ch;
        }
    }
    return pasA + pasB;
}

Decoding

This is how to decode the stuff:

/// <summary>
/// Decodes stuff into plain text
/// </summary>
/// <param name="input">The string to decode</param>
/// <returns>The decoded result</returns>
public static string DeCode(string input)
{
    int lnl = (int)Math.Round((decimal)input.Length / 2);
    //Write Strings
    char[] ln1, ln2;
    ln1 = input.Substring(0, lnl).ToCharArray();
    ln2 = input.Substring(lnl).ToCharArray();
#if DEBUG
    Debug.WriteLine("Line 1: " + input.Substring(0, lnl));
    Debug.WriteLine("Line 2: " + input.Substring(lnl, input.Length - lnl));
#endif
    //Writen strings, now seperate into one
    bool top = true;
    string output = "";
    int x, topx, botx;
    x = 1; topx = 0; botx = 0;
    while( x != input.Length + 1)
    {
        if(top == true)
        {
            if(topx > ln1.Length - 1)
            {
                return output;
            }
            output += ln1[topx]; topx += 1; top = false;
#if DEBUG
            Debug.WriteLine("topx: " + topx + " ln1 length: " + ln1.Length);
            #endif
        }
        else
        {
            output += ln2[botx]; botx += 1; top = true;
        }
        x++;
    }
    return output;
}