RailFence Algorithm

using System;
using System.Linq;
using Laba1.Interfaces;

namespace Laba1.Algorithms
{
    public class RailFence : IAlgorithm
    {
        public string Decrypt(string text, string key)
        {
            int rkey = Convert.ToInt32(key);
            char[,]  charMatrix = new char[rkey, text.Length];
            bool dir_down = false;
            int row = 0, col = 0;
            for (int i = 0; i < text.Length; i++)
            {
                if (row == 0 || row == rkey - 1)
                    dir_down = !dir_down;
                charMatrix[row, col++] = '*';
                if (dir_down)
                    row++;
                else
                    row--;
            }
            int ind = 0;
            for (int i = 0; i < rkey; i++)
            {
                for (int j = 0; j < text.Length; j++)
                {
                    if (charMatrix[i, j] == '*')
                        charMatrix[i, j] = text[ind++];
                }
            }
            string resultText = "";
            row = 0;
            col = 0;
            for (int i = 0; i < text.Length; i++)
            {
                if (row == 0)
                    dir_down = true;
                if (row == rkey - 1)
                    dir_down = false;
                resultText += charMatrix[row, col++];
                if (dir_down)
                    row++;
                else
                    row--;
            }
            return resultText;
        }

        public string Encrypt(string text, string key)
        {
            var rkey = Convert.ToInt32(key);
            var matrix = new char[rkey, text.Length];
            int k = 0;
            int j = 0;
            int buf = 0;
            string resultString = "";
            while (k < text.Length)
            {
                for (int i = 0; (i < rkey) && (j < text.Length); i++)
                {
                    matrix[i, buf] = text[buf];
                    buf = ++j;
                    k++;
                }
                for (int i = rkey - 2; (i > 0) && (j < text.Length); i--)
                {
                    matrix[i, buf] = text[buf];
                    buf = ++j;
                    k++;
                }
            }
            k = 0;
            while (k < text.Length)
            {
                for (int i = 0; i < rkey; i++)
                {
                    for (int y = 0; y < text.Length; y++)
                    {
                        if (matrix[i, y] != '\0')
                            resultString += matrix[i, y];
                        k++;
                    }
                }
            }
            return resultString;
        }
    }
}