public void CreateStegoFile(string inPath1, string message, string password, string inPath2)
{
// Mo file dau vao
FileStream inStream = new FileStream(inPath1, FileMode.Open, FileAccess.Read);
// kiem tra xem co phai anh bitmap 24 bits khong
char b = (char)inStream.ReadByte();
char m = (char)inStream.ReadByte();
if (!(b == 'B' && m == 'M'))
{
throw new Exception("Khong phai la anh bitmap");
}
// kiem tra xem co phai la anh 24 bit hay k
inStream.Seek(28, 0); // dua con tro ve vi tri byte thu 28
byte[] temp = new byte[2];
inStream.Read(temp, 0, 2); // so bit/1pixel duoc luu bang 2 byte
Int16 nBit = BitConverter.ToInt16(temp, 0); // chuyen mang byte temp[] ve so nguyen 16 bit
if (nBit != 24)
{
throw new Exception("Day khong phai la anh 24 bit");
}
// Doc 54 byte phan header roi dua vao trong outStream
int offset = 54;
inStream.Seek(0, 0);
byte[] header = new byte[offset];
inStream.Read(header, 0, offset);
//viet 54 byte nay vao trong file stego ( file dau ra)
FileStream outStream = new FileStream(inPath2, FileMode.Create, FileAccess.Write);
outStream.Write(header, 0, offset);
// ma hoa thong diep va mat khau thanh 1 thong diep duy nhat
UnicodeEncoding unicode = new UnicodeEncoding();
byte[] newMessageByte = AddMessLengthToAhead(unicode.GetBytes(message)); // them 4 byte do dai cua message vao dau cua thong diep
// thuc hien tron
newMessageByte = CryptoHelper.Encrypt(newMessageByte, password);
// thuc hien giau thong diep nay vao trong anh
inStream.Seek(offset, 0); // dua con tro ve noi bat dau cua Data o vi tri thu 54 (offset=54)
LSBHelper.Encode(inStream, newMessageByte, outStream); //thay tung bit cua thong diep vao LSB cua inStream va ghi ra outStream
inStream.Close(); // dong file anh dau vao
outStream.Close();
}
private void BTNGIAIMA_Click(object sender, EventArgs e)
{
string password = TXTMATKHAU.Text;
// kiem tra xem dau vao co hop le khong? neu khong tao ra cac exception
if (inPath2 == "")
{
MessageBox.Show("Bạn chưa chọn ảnh để giả mã");
}
else if (password == "")
{
MessageBox.Show("Bạn chưa nhập mật khẩu");
}
else
{
try
{
// kiem tra xem file dau vao co phai la file Bitmap 24 bit khong?
FileStream inStream = new FileStream(inPath2, FileMode.Open, FileAccess.Read);
inStream.Seek(0, 0); // dua con tro ve dau file
char b = (char)inStream.ReadByte();
char m = (char)inStream.ReadByte();
if (!(b == 'B' && m == 'M'))
{
throw new Exception("Day khong phai la file Bitmap");
}
// kiem tra xem co phai anh bitmap 24 bit khong
int offset = 28;
inStream.Seek(offset, 0);
byte[] temp = new byte[2]; // doc vao 2 byte
inStream.Read(temp, 0, 2); // vi tri 28 va 29
// chuyen temp[] ve so nguyen 16 bit
Int16 numOfBit = BitConverter.ToInt16(temp, 0);
if (numOfBit != 24)
{
throw new Exception("Khong phai anh 24 bit");
}
// bat dau tham nhap vao phan data
offset = 54;
inStream.Seek(offset, 0);
byte[] bLen = new byte[4]; // 4 byte luu tru do dai thong diep
bLen = LSBHelper.Decode(inStream, 4); // cho nay khong the dung method FileStream.Read duoc,do 4 byte nay thuc chat la 32 byte trong inStream
//decrypt 4 byte nay de duoc 4 byte thuc su ban dau (do ca 4 byte nay cung duoc ma hoa boi khoa Key[128])
bLen = CryptoHelper.Decrypt(bLen, password);
int length = BitConverter.ToInt32(bLen, 0); // chuyen tu mang byte thanh so nguyen
// thuc hien doc ra mang thong diep an (van bi Encrypt)
inStream.Seek(offset + 4 * 8, 0); // 32 byte dau tien de luu do dai cua thong diep
byte[] buffer = new byte[length]; // su dung mang nay de luu tru tam
try
{
buffer = LSBHelper.Decode(inStream, length);
}
catch { throw new Exception("Anh nay khong chua thong tin hoac ban da nhap sai mat khau"); } // trong qua trinh trich xuat ra thong diep giau ,neu gap 1 ngoai le nao do,coi nhu trich xuat khong thanh cong ( thong thuong ngoai le phat sinh se la khong du bo nho)
byte[] realHidenMessage = new byte[4 + buffer.Length];
realHidenMessage = ConcatTwoByteArray(bLen, buffer); // them 4 byte vao dau de tien cho viec Decrypt
realHidenMessage = CryptoHelper.Decrypt(realHidenMessage, password); // bay gio ta da duoc mang thong diep thuc su
byte[] hidenMessage = new byte[length]; // bay gio ta chi quan tam den phan thong diep
for (int i = 0; i < length; i++)
{
hidenMessage[i] = realHidenMessage[i + 4];
}
// chuyen ve dang string
UnicodeEncoding unicode = new UnicodeEncoding();
string result = unicode.GetString(hidenMessage);
TXTTHONGTIN.Text = result; // hien thi ket qua ra textbox
inStream.Close(); // dong file dau vao
}
catch
{
MessageBox.Show("Giải Mã Thất Bại");
}
}
}
