/// <summary>
/// encrypt or decrypt a byte[] array
/// </summary>
/// <param name="encrypt">ENCRYPT - encrypt (true), DECRYPT - decrypt (false)</param>
public static byte[] Encode(StreamCtx ctx, byte[] data, bool encrypt)
{
MemoryStream instr = null, outstr = null;
byte[] output = null;
try
{
instr = new MemoryStream(data, false);
outstr = new MemoryStream((data.Length - (data.Length % ctx.BlockSize())) + ctx.BlockSize());
if (encrypt)
{
Encrypt(ctx, instr, outstr);
}
else
{
Decrypt(ctx, instr, outstr);
}
outstr.Seek(0, SeekOrigin.Begin);
output = new byte[outstr.Length];
outstr.Read(output, 0, output.Length);
}
finally
{
if (instr != null)
{
instr.Close();
}
if (outstr != null)
{
outstr.Close();
}
}
return(output);
}
/// <summary>
/// creates the context to be used by the other methods
/// once created the context is readonly
/// use always this method (or its overwrites) to obtain a context
/// </summary>
/// <param name="ibc">this method will call InitCipher, you dot not need to call it before</param>
/// <param name="key">make sure the length of the key is as required
/// some ciphers have key size restrictions</param>
/// <param name="iv">is ignored in EBC mode</param>
/// <param name="mode"></param>
/// <returns></returns>
public static StreamCtx MakeStreamCtx(IBlockCipher ibc, byte[] key, byte[] iv, StreamCipher.Mode mode)
{
StreamCtx ctx = new StreamCtx();
ctx.Ibc = ibc;
ctx.Ibc.InitCipher(key);
ctx.IV = iv;
ctx.Mode = mode;
ctx.MakeReadOnly();
return(ctx);
}
/// <summary>
/// just to make stream encryption have the same interface as for bytes
/// buffer streams before passing them to this method
/// </summary>
public static void Encode(StreamCtx ctx, Stream instr, Stream outstr, bool encrypt)
{
if (encrypt)
{
Encrypt(ctx, instr, outstr);
}
else
{
Decrypt(ctx, instr, outstr);
}
}
/// <summary>
/// encrypts Stream instr to outStr
/// buffer streams before passing them to this method
/// </summary>
public static void Encrypt(StreamCtx ctx, Stream instr, Stream outstr)
{
if (instr.Length <= 0)
{
return;
}
byte[] buffer = new byte[ctx.BlockSize()];
byte[] output = new byte[ctx.BlockSize()];
bool ivInited = false;
int i = 0;
do
{
i = instr.Read(buffer, 0, ctx.BlockSize());
if (i < 0)
{
i = 0;
}
if ((i > 0) && (!ivInited)) // first block
{
ivInited = true;
if (ctx.Mode == Mode.CBC)
{
Array.Copy(ctx.IV, 0, output, 0, output.Length);
}
}
if ((i <= 0) || (i < buffer.Length)) // lastBlock
{
PrepareLastBuffer(buffer, i);
PrepareBuffer(ctx.Mode, buffer, output);
ctx.Ibc.Cipher(buffer, output);
outstr.Write(output, 0, output.Length);
break;
}
PrepareBuffer(ctx.Mode, buffer, output);
ctx.Ibc.Cipher(buffer, output);
outstr.Write(output, 0, output.Length);
} while (true);
outstr.Flush();
}
/// <summary>
/// decrypts Stream instr to outStr
/// buffer streams before passing them to this method
/// </summary>
public static void Decrypt(StreamCtx ctx, Stream instr, Stream outstr)
{
// in this method we fail silently
if (instr.Length <= 0)
{
return;
}
byte[] buffer = new byte[ctx.BlockSize()];
byte[] output = new byte[ctx.BlockSize()];
int i = 0;
bool ivInited = false;
byte[] iv = new byte[ctx.BlockSize()];
// to delay the output, required because we do not rely in
// instr.Length to find the end of stream
bool lastInited = false;
byte[] last = new byte[ctx.BlockSize()];
do
{
i = instr.Read(buffer, 0, buffer.Length);
if (i < 0)
{
i = 0;
}
// must be a multiple of ctx.blockSize
if ((i > 0) && (i != buffer.Length))
{
return; //throw new Exception();
}
if ((i > 0) && (!ivInited))
{
ivInited = true;
if (ctx.Mode == Mode.CBC)
{
Array.Copy(ctx.IV, 0, iv, 0, ctx.IV.Length);
}
}
if (i <= 0) //lastblock
{
// buffer has no data
if (!lastInited)
{
return; // throw new Exception();
}
Array.Copy(last, output, output.Length);
// remove padd data
int k = (int)output[output.Length - 1];
if (k > output.Length)
{
return;
}
outstr.Write(output, 0, output.Length - k);
break;
}
ctx.Ibc.InvCipher(buffer, output);
if (ctx.Mode == Mode.CBC)
{
PrepareBuffer(ctx.Mode, output, iv);
Array.Copy(buffer, iv, buffer.Length);
}
//delay output
if (!lastInited)
{
Array.Copy(output, last, output.Length);
lastInited = true;
}
else
{
outstr.Write(last, 0, last.Length);
Array.Copy(output, last, output.Length);
}
} while (true);
outstr.Flush();
}