/// <summary>
/// The method decodes ciphertext with a cipher "Rail-Fence" with the specified key.
/// </summary>
/// <param name="ciphertext">Text to decrypt.</param>
/// <param name="key">Fence height.</param>
/// <returns>Decrypted text.</returns>
public string Decrypt(string ciphertext, string key)
{
int numericKey;
int.TryParse(KeyValidation.ModifyKey(key, TypesOfCiphers.RailFence), out numericKey);
if (numericKey == 0)
{
numericKey = 1;
}
int currentPos = 0;
char[] plaintext = new char[ciphertext.Length];
for (int rowNumber = 0; rowNumber < numericKey; rowNumber++)
{
for (int i = rowNumber, currentCharInStr = 0; i < ciphertext.Length;
i += GetIndexNextChar(currentCharInStr, rowNumber, numericKey), currentCharInStr++)
{
plaintext[i] = ciphertext[currentPos++];
}
}
return(new string(plaintext));
}
private void BtnDecrypt_Click(object sender, EventArgs e)
{
TypesOfCiphers typesOfCipher = TypesOfCiphers.RailFence;
if (rbRailFence.Checked)
{
typesOfCipher = TypesOfCiphers.RailFence;
}
else if (rbRotatingSquare.Checked)
{
typesOfCipher = TypesOfCiphers.RotatingSquare;
}
else if (rbVigenerCipher.Checked)
{
typesOfCipher = TypesOfCiphers.Vigenere;
}
tbKey.Text = KeyValidation.ModifyKey(tbKey.Text, typesOfCipher).ToString();
rtbSrcText.Text = TextValidation.ModifyText(rtbSrcText.Text, typesOfCipher);
if (cbUseDataInRcb.Checked)
{
rtbResText.Text = MainController.Decrypt(rtbSrcText.Text, tbKey.Text,
typesOfCipher);
}
else
{
try
{
MainController.Decrypt(tbPathToSrcFile.Text, tbPathToResFile.Text,
tbKey.Text, typesOfCipher);
}
catch (ArgumentException)
{
MessageBox.Show("Incorrect file path entered!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
catch (IOException)
{
MessageBox.Show("Incorrect file path entered!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}
}
/// <summary>
/// The method encodes plaintext with a cipher "Rail-Fence" with the specified key.
/// </summary>
/// <param name="plaintext">Text to be encrypted.</param>
/// <param name="key">Fence height.</param>
/// <returns>The ciphertext.</returns>
public string Encrypt(string plaintext, string key)
{
int numericKey;
int.TryParse(KeyValidation.ModifyKey(key, TypesOfCiphers.RailFence), out numericKey);
if (numericKey == 0)
{
numericKey = 1;
}
string ciphertext = null;
for (int rowNumber = 0; rowNumber < numericKey; rowNumber++)
{
for (int i = rowNumber, currentCharInStr = 0; i < plaintext.Length;
i += GetIndexNextChar(currentCharInStr, rowNumber, numericKey), currentCharInStr++)
{
ciphertext += plaintext[i];
}
}
return(ciphertext);
}