public void Decrypt()
{
char[] keywordChars = Keyword.ToCharArray();
char[] encryptedMessage = MessageString.ToCharArray();
char[] unencryptedMessage = new char[MessageString.Length];
int alphabetMatrixLineNumber = 0;
for (int i = 0; i < encryptedMessage.Length; i++)
{
// All the letters in the charToIntDictionary are stored in upper case, so it's important that each letter is converted to an uppercase value
// or else the Dictionary search will fail
char letter = char.ToUpper(encryptedMessage[i]);
if (!char.IsLetter(letter))
{
unencryptedMessage[i] = letter;
continue;
}
// If the loop has iterated through every row in the alphabetMatrix, it will be reset to start on the first row again
if (alphabetMatrixLineNumber == keywordChars.Length)
{
alphabetMatrixLineNumber = 0;
}
// Gets the position of the first letter of the current row of the alphabetMatrix
// This position can be used to calculate how offset each character is in regards to their original position in the alphabet
// For example:'W' is the 23rd letter in the alphabet, which means that the current letter in the encrypted message is 4 positions out of place.
// We can then find the current letter's original position in the alphabet and add 4 to find the original letter (which is 'H').
int charOffset = 26 - charToIntDictionary[char.ToUpper(keywordChars[alphabetMatrixLineNumber])];
// If the letter's position hasn't changed, append it
if (charOffset == 26)
{
unencryptedMessage[i] = letter;
}
else
{
// Gets the position of the current character and finds it's position in the 'normal' alphabet.
// It's original letter is then calculated by adding the offset to the letter's current position
int originalLetterlPositionInAlphabet = charToIntDictionary[letter];
int characterPosition = originalLetterlPositionInAlphabet + charOffset;
// If the addition goes over 25, then the alphabet has looped back round to the beginning, so subtracting 26 from the total
// will give us a value towards the beginning of the alphabet
if (originalLetterlPositionInAlphabet + charOffset > 25)
{
characterPosition -= 26;
}
unencryptedMessage[i] = intToCharDictionary[characterPosition];
}
alphabetMatrixLineNumber++;
}
MessageString = new string(unencryptedMessage);
CreationDate = DateTime.Now;
}
public void Encrypt()
{
AlphabetGenerator alphabet = new AlphabetGenerator(Keyword);
char[] unencryptedMessage = MessageString.ToCharArray();
char[] encryptedMessage = new char[MessageString.Length];
int alphabetMatrixLineNumber = 0;
for (int i = 0; i < unencryptedMessage.Length; i++)
{
// All the letters in the charToIntDictionary are stored in upper case, so it's important that each letter is converted to an uppercase value
// or else the Dictionary search will fail
char letter = char.ToUpper(unencryptedMessage[i]);
if (!char.IsLetter(letter))
{
encryptedMessage[i] = letter;
continue;
}
// If the loop has iterated through every row in the alphabetMatrix, it will be reset to start on the first row again
if (alphabetMatrixLineNumber == alphabet.Matrix.GetLength(1))
{
alphabetMatrixLineNumber = 0;
}
// Finds the letter's position in the alphabet and assigns the value that is in it's position in the alphabet matrix
int letterPosition = charToIntDictionary[letter];
encryptedMessage[i] = alphabet.Matrix[letterPosition, alphabetMatrixLineNumber];
alphabetMatrixLineNumber++;
}
MessageString = new string(encryptedMessage);
CreationDate = DateTime.Now;
}
