public static void BC()
{
Random r = new Random();
byte[] input = new byte[1 << 4];
byte[] key = new byte[1 << 4];
r.NextBytes(input);
r.NextBytes(key);
Console.WriteLine("Input:");
print(input);
Console.WriteLine("Key:");
print(key);
blockCipher Block = new blockCipher(input, key);
Console.WriteLine("EN:");
print(Block.encrypt());
blockCipher Block2 = new blockCipher(Block.encrypt(), key);
Console.WriteLine("DC:");
print(Block2.decrypt());
}
/// <summary>
/// Encrypt a given source file and save it to a given target file.
/// </summary>
/// <param name="sourceFileName">The filename of the source file. Presumed to exist.</param>
/// <param name="destinationFileName">The filename of the target file. Will be overwritten.</param>
/// <param name="key">The key to encrypt with</param>
/// <param name="mode">The mode of encryption. Use Engine.* constants.</param>
/// <param name="blockSize">The chosen block size.</param>
public static void StartEncryption(String sourceFileName, String destinationFileName, String key, byte mode, int blockSize = 16)
{
if (mode != ECB && mode != CBC && mode != CFB && mode != OFB)
{
throw new Exception("Invalid block cipher mode of operation.");
}
// Auxiliary variables
byte[] crlf = { Convert.ToByte('\r'), Convert.ToByte('\n') };
// Key processing
char[] keyChars = key.ToCharArray();
int keyLength = Math.Max(key.Length, blockCipherEnDc.SIZE);
byte[] keyBytes = new byte[keyLength];
for (var i = 0; i < keyLength; ++i)
{
if (i < key.Length)
{
keyBytes[i] = Convert.ToByte(keyChars[i]);
}
else
{
keyBytes[i] = 0;
}
}
// Open read handle. Treat all files as binary.
FileStream fr = File.OpenRead(sourceFileName);
BinaryReader br = new BinaryReader(fr);
// Open write handle.
FileStream fw = File.OpenWrite(destinationFileName);
BinaryWriter bw = new BinaryWriter(fw);
// Start by writing the header
// The header consists of the following bytes:
// 1-8 Original file length
// 9-12 Block Size
// 13 Block cipher mode of operation
// 14-15 CRLF
// 16-.. Initialization vector (according to blocksize)
// ..-.. CRLF
Int64 originalLength = Convert.ToInt64(fr.Length);
Console.WriteLine(originalLength.ToString("X8"));
bw.Write(originalLength);
Int32 blockSizeField = Convert.ToInt32(blockSize);
bw.Write(blockSizeField);
bw.Write(mode);
bw.Write(crlf);
Random iv = new Random();
byte[] initializationVector = new byte[blockSize];
iv.NextBytes(initializationVector);
bw.Write(initializationVector);
bw.Write(crlf);
// Header is written.
// Write body
long pos = 0;
long length = fr.Length;
byte[] readBuffer;
byte[] paddedBuffer;
blockCipher Cipher;
byte[] previousBlock = (byte[])initializationVector.Clone();
while (pos < length)
{
// Load one block into buffer
readBuffer = br.ReadBytes(blockSize);
paddedBuffer = PadByteArray(readBuffer, blockSize);
byte[] cipherBuffer;
byte[] pre;
switch (mode)
{
case ECB:
Cipher = new blockCipher(paddedBuffer, keyBytes);
bw.Write(Cipher.encrypt());
break;
case CBC:
pre = XorByteArray(paddedBuffer, previousBlock);
Cipher = new blockCipher(pre, keyBytes);
cipherBuffer = Cipher.encrypt();
bw.Write(cipherBuffer);
Array.Copy(cipherBuffer, previousBlock, blockSize);
break;
case CFB:
Cipher = new blockCipher(previousBlock, keyBytes);
pre = Cipher.encrypt();
cipherBuffer = XorByteArray(pre, paddedBuffer);
bw.Write(cipherBuffer);
Array.Copy(cipherBuffer, previousBlock, blockSize);
break;
case OFB:
Cipher = new blockCipher(previousBlock, keyBytes);
pre = Cipher.encrypt();
cipherBuffer = XorByteArray(paddedBuffer, pre);
bw.Write(cipherBuffer);
Array.Copy(pre, previousBlock, blockSize);
break;
default:
break;
}
pos += blockSize;
}
// Body is written.
// Close write handle
bw.Close();
fw.Close();
// Close read handle
br.Close();
fr.Close();
}
/// <summary>
/// Decrypt a given source file and save it to a given target file.
/// </summary>
/// <param name="sourceFileName">The filename of the source file. Presumed to exist.</param>
/// <param name="destinationFileName">The filename of the target file. Will be overwritten.</param>
/// <param name="key">The key to decrypt with.</param>
public static void StartDecryption(String sourceFileName, String destinationFileName, String key)
{
// Auxiliary variables
int readPos = 0; // Reading position
Int64 originalFileSize = 0; // Original file size
Int64 remainingBody = 0; // Bytes left to read
Int32 blockSize = 0;
byte cipherMode = 0;
byte cr = Convert.ToByte('\r');
byte lf = Convert.ToByte('\n');
byte[] initializationVector;
char[] keyChars = key.ToCharArray();
int keyLength = Math.Max(key.Length, blockCipherEnDc.SIZE);
byte[] keyBytes = new byte[keyLength];
for (var i = 0; i < keyLength; ++i)
{
if (i < key.Length)
{
keyBytes[i] = Convert.ToByte(keyChars[i]);
}
else
{
keyBytes[i] = 0;
}
}
// Open read handle. Treat all files as binary.
FileStream fr = File.OpenRead(sourceFileName);
BinaryReader br = new BinaryReader(fr);
// Open write handle.
FileStream fw = File.OpenWrite(destinationFileName);
BinaryWriter bw = new BinaryWriter(fw);
// Read header
// 1. Original filesize
originalFileSize = br.ReadInt64();
readPos += sizeof(Int64);
// 2. Block size
blockSize = br.ReadInt32();
readPos += sizeof(Int32);
// 3. Cipher mode
cipherMode = br.ReadByte();
readPos += sizeof(byte);
// 4. CRLF -- validate their existence
if (br.ReadByte() != cr)
{
throw new Exception("Invalid ciphertext header.");
}
readPos += sizeof(byte);
if (br.ReadByte() != lf)
{
throw new Exception("Invalid ciphertext header.");
}
readPos += sizeof(byte);
// 5. Initialization vector
initializationVector = br.ReadBytes(blockSize);
readPos += blockSize;
// 6. CRLF again -- validate their existence
if (br.ReadByte() != cr)
{
throw new Exception("Invalid ciphertext header.");
}
readPos += sizeof(byte);
if (br.ReadByte() != lf)
{
throw new Exception("Invalid ciphertext header.");
}
readPos += sizeof(byte);
// We're done with the header, we can now proceed to the body.
remainingBody = originalFileSize;
byte[] previousBlock = initializationVector;
while (readPos < fr.Length)
{
byte[] cipherBuffer = br.ReadBytes(blockSize);
byte[] toWrite = new byte[blockSize];
byte[] plainBuffer;
byte[] preXor;
blockCipher Cipher;
// Decrypt the buffer and write to destination file
switch (cipherMode)
{
case ECB:
Cipher = new blockCipher(cipherBuffer, keyBytes);
plainBuffer = Cipher.decrypt();
toWrite = plainBuffer;
break;
case CBC:
Cipher = new blockCipher(cipherBuffer, keyBytes);
preXor = Cipher.decrypt();
plainBuffer = XorByteArray(preXor, previousBlock);
toWrite = plainBuffer;
previousBlock = cipherBuffer;
break;
case CFB:
Cipher = new blockCipher(previousBlock, keyBytes);
preXor = Cipher.encrypt();
plainBuffer = XorByteArray(preXor, cipherBuffer);
toWrite = plainBuffer;
previousBlock = cipherBuffer;
break;
case OFB:
Cipher = new blockCipher(previousBlock, keyBytes);
preXor = Cipher.encrypt();
plainBuffer = XorByteArray(preXor, cipherBuffer);
toWrite = plainBuffer;
previousBlock = preXor;
break;
default:
break;
}
if (remainingBody < blockSize)
{
byte[] writeBuffer = new byte[remainingBody];
Array.Copy(toWrite, writeBuffer, (int)remainingBody);
bw.Write(writeBuffer);
}
else
{
bw.Write(toWrite);
}
readPos += blockSize;
remainingBody -= blockSize;
}
// Mode is read from the header of the file
// Close write handle
bw.Close();
fw.Close();
// Close read handle
br.Close();
fr.Close();
}
