public static byte[][] GenerateSubTables()
{
var rows = new byte[0x100][];
for (int i = 0; i < 0x100; i++)
{
rows[i] = CriHcaKey.CreateRandomRow((byte)i);
}
return(rows);
}
/// <summary>
/// Finds possible tables used to shuffle the decryption table with a known upper seed
/// </summary>
/// <remarks>
/// As in <see cref="FilterPossibleShufflersWithByte2Zeros"/>, we search each possible shuffle table
/// to find one with at least 9 rows of all zeros. The difference is this time we know which specific
/// rows need to be all zeros, the rows containing the upper nibbles 7 through 0xf.
/// The two shuffler IDs correspond to the positions of the bytes 0 or 0xFF in the table, so this is
/// used to further filter the possible shufflers.
/// </remarks>
public void FindShuffleTable()
{
byte[] upperSubTable = SubTables[UpperSeed];
byte[] inverseSubTable = CriHcaKey.InvertTable(upperSubTable);
int[] count = new int[16];
var possibleShufflers = new List <ShufflerId>();
byte row0 = inverseSubTable[0];
byte rowF = inverseSubTable[0xf];
foreach (var s in PossibleShufflers)
{
// Count the number of zeros in each row
Array.Clear(count, 0, 16);
foreach (byte v in Byte2Zeros)
{
int unshuffledUpperNibble = BackwardShuffle[s.Pos1][s.Pos2][v] >> 4;
count[unshuffledUpperNibble]++;
}
bool valid = true;
// Invalidate the tables without the required empty rows
for (int i = 0; i < upperSubTable.Length; i++)
{
for (int j = 7; j < 15; j++)
{
if (count[inverseSubTable[j]] < 16)
{
valid = false;
}
}
if (count[inverseSubTable[15]] < 15)
{
valid = false;
}
}
// Invalidate the tables without the bytes 0x00 and 0xFF in their proper rows
if ((s.Pos1 >> 4 != row0 && s.Pos1 >> 4 != rowF) ||
(s.Pos2 >> 4 != row0 && s.Pos2 >> 4 != rowF) ||
s.Pos1 >> 4 == s.Pos2 >> 4)
{
valid = false;
}
if (valid)
{
possibleShufflers.Add(s);
}
}
PossibleShufflers = possibleShufflers;
}
public static byte[] GenerateShuffler(int a, int b, bool backward)
{
byte[] table = new byte[256];
byte x = 0;
int outPos = 1;
for (int i = 0; i < 256; i++)
{
x += 17;
if (x != a && x != b)
{
table[outPos++] = x;
}
}
return(backward ? table : CriHcaKey.InvertTable(table));
}