public long Decrypt(Tuple tuple, Key.PrivateKey key)
{
var a = tuple.a;
var b = tuple.b;
var p = key.P;
var x = key.X;
// q = (a^x)^-1
var q = modular_pow(a, p - 1 - x, p);
var m = (b * q) % p;
return m;
}
public void Decrypt(string sourceFileName, string targetFileName, Key.PrivateKey key)
{
// Fetch tuples
tuples = ReadTuplesFromFile(sourceFileName, key);
System.Diagnostics.Debug.WriteLine("Count Decrypt : " + tuples.Count());
// Calculate byte length
// byteLength is used to determine how to write to the target file
var byteLength = getByteLength(key.P);
// Open filewrite handle
var bw = new BinaryWriter(File.Open(targetFileName, FileMode.Create));
// Loop through each tuple, decrypt, and write
long m;
foreach (var t in tuples)
{
// Decrypt
m = Decrypt(t, key);
// Write
// TODO if number of bytes is not power of 2
switch (getByteLength(m))
{
case 1:
bw.Write((byte)m);
break;
case 2:
bw.Write((short)m);
break;
case 4:
bw.Write((int)m);
break;
case 8:
bw.Write((long)m);
break;
case 16:
bw.Write((decimal)m);
break;
}
// Written.
}
bw.Close();
}
private void button1_Click(object sender, EventArgs e)
{
if (!validate_generate_key())
{
MessageBox.Show("X and G must be less than p");
return;
}
// Generate Key Button
SaveFileDialog fileBrowser = new SaveFileDialog();
if (fileBrowser.ShowDialog() == DialogResult.OK)
{
string fileName = fileBrowser.FileName;
Key key = new Key((long)key_generate_p.Value, (long)key_generate_g.Value,
(long)key_generate_x.Value);
key.saveToFile(fileName);
}
}
public void Encrypt(string fileName, Key.PublicKey key)
{
tuples.Clear();
FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
// Block Message Length based on value of P in key
int blockLength = getBitLength(key.P);
int n_blockLength = blockLength;
// byte to read from file
int n_byte = 8;
int byte_read = fs.ReadByte();
// Message that want to be encrypt
long message = 0;
// Process Message
while (byte_read >= 0)
{
int temp_bit = -1;
while (byte_read >= 0 && message < key.P && n_blockLength > 0)
{
if (n_byte == 0)
{
// Read next byte of file
byte_read = fs.ReadByte();
n_byte = 8;
if (byte_read < 0) break;
}
int bit = (byte_read >> (n_byte - 1)) % 2 == 0 ? 0 : 1;
message = (message << 1 )+ bit;
n_byte--;
n_blockLength--;
}
// if Message more than block or P
if (message >= key.P || n_blockLength < 0)
{
temp_bit = (byte_read >> (n_byte - 1)) % 2 == 0 ? 0 : 1;
message = message >> 1;
}
long k = key.P-2; // Must be random
long a = modular_pow(key.G, k, key.P);
long b = modular_pow(message, key.Y, k, key.P);
Tuple t = new Tuple();
t.a = a;
t.b = b;
tuples.Add(t);
message = 0;
n_blockLength = blockLength;
// if only the temp_bit have any value
if (temp_bit >= 0)
{
message = message << 1 + temp_bit;
n_blockLength--;
}
}
fs.Close();
}
private void saveKeysButton_Click(object sender, RoutedEventArgs e)
{
try
{
// Fetch ingredients for private key
long p = Convert.ToInt64(pTextBox.Text);
long g = Convert.ToInt64(gTextBox.Text);
long x = Convert.ToInt64(xTextBox.Text);
// Generate key
Key k = new Key(p, g, x);
ElGamalApplication.Key.PrivateKey pri = k.GeneratePrivateKey();
ElGamalApplication.Key.PublicKey pub = k.GeneratePublicKey();
SaveFileDialog fileBrowser = new SaveFileDialog();
Nullable<bool> result = fileBrowser.ShowDialog();
if (result == true)
{
string fileName = fileBrowser.FileName;
k.saveToFile(fileName);
}
}
catch (Exception ex)
{
ShowMessageBox("Key generation failed.");
}
}
private void generatePrivateKeyButton_Click(object sender, RoutedEventArgs e)
{
try
{
// Fetch ingredients for private key
long p = Convert.ToInt64(pTextBox.Text);
long g = Convert.ToInt64(gTextBox.Text);
long x = Convert.ToInt64(xTextBox.Text);
// Generate key
Key k = new Key(p, g, x);
ElGamalApplication.Key.PrivateKey pri = k.GeneratePrivateKey();
ElGamalApplication.Key.PublicKey pub = k.GeneratePublicKey();
xTextBox.Text = pri.X.ToString();
yTextBox.Text = pub.Y.ToString();
}
catch (Exception ex)
{
ShowMessageBox("Key generation failed.");
}
}
public void Encrypt(string fileName, Key.PublicKey key)
{
tuples.Clear();
FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
// Block Message Length based on value of P in key
int blockLength = getByteLength(key.P);
int n_blockLength = blockLength;
System.Diagnostics.Debug.WriteLine(blockLength);
// byte to read from file
int byte_read = 0;
// Message that want to be encrypt
long message = 0;
// Process Message
while (byte_read >= 0)
{
int temp_byte = -1;
while (byte_read >= 0 && message < key.P && n_blockLength > 0)
{
byte_read = fs.ReadByte();
if (byte_read < 0) break;
message = 256 * message + byte_read;
n_blockLength--;
System.Diagnostics.Debug.WriteLine((char)byte_read);
}
// if Message more than block or P
if (message >= key.P )
{
temp_byte = byte_read;
message = message/256;
}
long k = 1520; // Must be random
long a = modular_pow(key.G, k, key.P);
long b = modular_pow(message, key.Y, k, key.P);
Tuple t = new Tuple();
t.a = a;
t.b = b;
tuples.Add(t);
System.Diagnostics.Debug.WriteLine("process :" + (char)message + "," + message);
//Console.WriteLine(message);
message = 0;
n_blockLength = blockLength;
// if only the temp_bit have any value
if (temp_byte >= 0)
{
message = message*256 + temp_byte;
n_blockLength--;
}
}
System.Diagnostics.Debug.WriteLine("Count Encrypt : " + tuples.Count());
fs.Close();
}
public List<Tuple> ReadTuplesFromFile(string fileName, Key.PrivateKey key)
{
var tuples = new List<Tuple>();
// Read text - init
BinaryReader br = new BinaryReader(File.OpenRead(fileName));
// Get block length
int blockLength = getByteLength(key.P);
int pos = 0;
char currentChar;
string hexString;
while (pos < br.BaseStream.Length)
{
br.ReadChar(); // (
++pos;
currentChar = br.ReadChar();
++pos;
hexString = "";
while (currentChar != ',')
{
hexString += currentChar;
currentChar = br.ReadChar();
++pos;
}
long a = long.Parse(hexString, System.Globalization.NumberStyles.HexNumber);
currentChar = br.ReadChar();
++pos;
hexString = "";
while (currentChar != ')')
{
hexString += currentChar;
currentChar = br.ReadChar();
++pos;
}
long b = long.Parse(hexString, System.Globalization.NumberStyles.HexNumber);
Tuple t = new Tuple();
t.a = a;
t.b = b;
tuples.Add(t);
}
return tuples;
}
