protected List <int> BytesToIndicesAndFill(byte[] plain, int columnCount, bool extraRow = false)
{
//we don't care about these values, it's probably better that
// we don't use the key-stream to generate them to not leak them at all.
// In some way, they will also act as pepper, so that's cool
IRng rng = new SysRng();
int remainder = plain.Length % columnCount;
int rowSize = columnCount;
int missingEntries = rowSize - remainder; //remainder == 0 ? 0 : rowSize - remainder;
List <int> plainIndices = plain.Select(ByteToIndex).ToList();
if (extraRow)
{
missingEntries += rowSize;
}
for (int i = 0; i < missingEntries - 1; ++i)
{
plainIndices.Add(rng.Next(_map.Count));
}
Debug.Assert(missingEntries < _map.Count);
plainIndices.Add(missingEntries);
return(plainIndices);
}
public override byte[] Encrypt(byte[] plain, byte[] key)
{
//Let's encrypt 8x8 or 16x16 at a time
//Insert padding amount at the beginning of the cypher so we know how much to remove
_matrixDimension = 8;
//if (plain.Length >= 16 * 16)
// _matrixDimension = 16;
_matrixSize = _matrixDimension * _matrixDimension;
//fix this
List <int> plainIxs = BytesToIndices(plain).ToList();
//calculate fill
int fill = _matrixDimension - plain.Length % _matrixDimension;
var noise = new SysRng();
for (int i = 0; i < fill; ++i)
{
plainIxs.Add(noise.Next(0, Alphabet.Count));
}
List <int> cypherIxs = new List <int>(plainIxs.Count + 4);
cypherIxs.AddRange(EncodeFill(fill, Alphabet.Count));
IRng rng = key.KeyToRand();
for (int i = 0; i < plainIxs.Count; i += _matrixDimension)
{
cypherIxs.AddRange(Encrypt(new ListSpan <int>(plainIxs, i, i + _matrixDimension), rng));
}
return(IndicesToBytes(cypherIxs));
}
public static List <byte[]> CreateFlips(byte[] buff, int num, IRng rng = null)
{
if (rng == null)
{
rng = new SysRng(123456);
}
var res = new List <byte[]>();
for (var ii = 0; ii < num; ++ii)
{
byte[] flip = new byte[buff.Length];
buff.CopyTo(flip, 0);
int flipByte = rng.Next(buff.Length);
int flipBit = rng.Next(8);
flip[flipByte] ^= (byte)(1 << flipBit);
res.Add(flip);
}
return(res);
}
