private static void HackCipher(SubstitutionPermutationNetwork spn, byte[] expectedKey, int iterationsCount)
{
var linearCryptoanalysis = new LinearCryptoanalysis(spn);
var bestLayerApproximations = linearCryptoanalysis.ChooseBestPathsStartingFromSingleSBoxInRound0(Exploit.maxSBoxesInLastRound, Exploit.maxSBoxesInRound, Exploit.thresholdBias).ToList();
Console.WriteLine($"Total approximations: {bestLayerApproximations.Count}");
var plains = Enumerable.Range(0, iterationsCount).Select(i => GenerateRandomPlainText()).ToArray();
var encs = plains.Select(plain => spn.EncryptBlock(plain)).ToArray();
var solutions = new List <Solution>();
foreach (var approximationsGroup in bestLayerApproximations
.Where(layer => layer.round0sboxNum % 8 == 6 || (layer.round0sboxNum % 8 == 7 && ((layer.round0x & 0x01) == 0)))
.GroupBy(layer => layer.ActivatedSboxesNums.Aggregate("", (s, num) => s + num))
.OrderBy(group => group.Key))
{
foreach (var approximation in approximationsGroup.Distinct().OrderByDescending(layer => layer.inputProbability.Bias()).Take(3))
{
solutions.AddRange(Exploit.HackApproximation(plains, encs, approximation, expectedKey));
}
}
Exploit.OrderSolutions(solutions, expectedKey);
}
public static void Do()
{
Console.WriteLine($"SPN: rounds {SubstitutionPermutationNetwork.RoundsCount}, blocksize {SubstitutionPermutationNetwork.BlockSizeBytes * 8 } bits");
var expectedKey = SubstitutionPermutationNetwork.GenerateRandomKey();
Console.WriteLine($"key: {expectedKey.ToHexUpperCase()}");
var spn = new SubstitutionPermutationNetwork(expectedKey);
var plainTextString = new string('X', SubstitutionPermutationNetwork.BlockSizeBytes);
var plainText = Encoding.ASCII.GetBytes(plainTextString);
var encryptedBytes = spn.EncryptBlock(plainText);
var decryptedBytes = spn.DecryptBlock(encryptedBytes);
var decryptedString = Encoding.ASCII.GetString(decryptedBytes);
Console.WriteLine($"{plainTextString} -> {encryptedBytes.ToHexUpperCase()} -> {decryptedString}");
HackCipher(spn, expectedKey, 6000);
}
