public static string DoDecryption(string cipertext, string filepath)
{
ArrayList result = new ArrayList(); // to add list of possible findings
string[] dictionary = Helper.GetDictionary(filepath); // list of words from dictionary file.
Hashtable charFrequency = Helper.GetKeyCodes(typeof(Helper.MinFrequency)); // to have list of char frequency in hashtable
Hashtable charList = Helper.GetCharTable(); // to maintain list of codes for each indexed char
string[] cipertextList = Helper.GetCipertextArray(cipertext, ','); // cipertext code array
Hashtable numList = new Hashtable(); // to maintain list of cipercode with its corresponding letters/chars
int ciperCharIndex = 0; // to point the index of current cibertext code
int prevCiperCharIndex = 0; // to maintain the previous index of last found word
bool shallIContinue2NextWord = true; // to toggle to skip the main dictionary loop when ciperchar index reached last code in cipertext.
foreach (string word in dictionary) // loop to pick each word in the dictionary list.
{
shallIContinue2NextWord = true; // always initialize to pick next word
Hashtable tempNumList = CopyHashtableFrom(numList);
bool isMatch = true;
foreach (char ch in word)
{
string key = ch.ToString();
string ciperCode = cipertextList[ciperCharIndex];
ArrayList charCodeArray = (ArrayList)charList[key];
if (!charCodeArray.Contains(ciperCode))
{
charCodeArray.Add(ciperCode);
}
if (charCodeArray.Count > (int)charFrequency[key])
{
isMatch = false; break;
}
if (tempNumList.ContainsKey(ciperCode))
{
if (tempNumList[ciperCode].ToString() != key)
{
isMatch = false;
break;
}
}
else
{
tempNumList.Add(ciperCode, key);
}
if (++ciperCharIndex >= cipertextList.Length)
{
ciperCharIndex = prevCiperCharIndex;
shallIContinue2NextWord = false;
break;
}
}
if (isMatch)
{
result.Add(word);
Console.WriteLine("Matching Word: {0}", word);
foreach (string key in numList.Keys)
{
Console.Write("[{0},{1}] ", key, numList[key]);
}
Console.WriteLine("------------------");
prevCiperCharIndex = ciperCharIndex;
numList = CopyHashtableFrom(tempNumList);
}
else
{
ciperCharIndex = prevCiperCharIndex;
foreach (string key in charList.Keys)
{
ArrayList arrayOfCharList = ((ArrayList)charList[key]);
arrayOfCharList.Clear();
foreach (string numKey in numList.Keys)
{
if (numList[numKey].ToString().Equals(key))
{
arrayOfCharList.Add(numKey);
}
}
}
}
if (!shallIContinue2NextWord)
{
break;
}
}
string resultString = string.Empty;
foreach (string word in result)
{
resultString += word;
}
return(resultString);
}