private List <DifferentialCharacteristic> GetPossibleSubstitutionOutcomes(int inputDifference, Dictionary <int, List <SubstitutionBoxOutput> > sBoxOutputs, double previosProbability = 1)
{
List <List <SubstitutionBoxOutput> > allOutputs = sBoxOutputs.Select(k => k.Value).ToList();
IEnumerable <IEnumerable <SubstitutionBoxOutput> > possibleOutcomes = allOutputs.CartesianProduct();
List <DifferentialCharacteristic> outcomes = new List <DifferentialCharacteristic>();
foreach (IEnumerable <SubstitutionBoxOutput> possibleOutcome in possibleOutcomes)
{
List <int> sBoxIndexes = sBoxOutputs.Keys.ToList();
int currentIndex = 0, output = 0;
double probability = previosProbability;
foreach (SubstitutionBoxOutput sBoxOutput in possibleOutcome)
{
output |= (sBoxOutput.Output << ((_spn.SubstitutionBoxCount - 1 - sBoxIndexes[currentIndex++]) * Substitution.InputLength));
probability *= sBoxOutput.Bias;
}
if (probability > LOWER_BOUND_PROBABILITY)
{
DifferentialCharacteristic characteristic = new DifferentialCharacteristic(inputDifference, output, probability);
characteristic.AddUsedSubstitionBoxForRound(possibleOutcome.ToList());
outcomes.Add(characteristic);
}
}
return(outcomes);
}
private List <DifferentialCharacteristic> GetPermutatedOutcomes(List <DifferentialCharacteristic> characteristics)
{
List <DifferentialCharacteristic> permutatedOutcomes = new List <DifferentialCharacteristic>();
foreach (DifferentialCharacteristic characteristic in characteristics)
{
int output = Permutation.Permutate(characteristic.OutputDifference);
DifferentialCharacteristic newCharacteristic = new DifferentialCharacteristic(characteristic.InputDifference, output, characteristic.Probability);
newCharacteristic.AddIntermediateOutputs(characteristic.IntermediateOutputs);
newCharacteristic.AddUsedSubstitionBoxes(characteristic.UsedSubstitutionBoxes);
permutatedOutcomes.Add(newCharacteristic);
}
return(permutatedOutcomes);
}
private List <DifferentialCharacteristic> GetCharacteristicForRound(DifferentialCharacteristic characteristic)
{
byte[] sBoxInputs = GetBytes(characteristic.OutputDifference);
Dictionary <int, List <SubstitutionBoxOutput> > sBoxOutputs = GetSubstitutionOutputs(sBoxInputs);
List <DifferentialCharacteristic> possibleOutcomes = GetPossibleSubstitutionOutcomes(characteristic.InputDifference, sBoxOutputs, characteristic.Probability);
possibleOutcomes.ForEach(e => {
e.AddIntermediateOutputs(characteristic.IntermediateOutputs);
e.AddIntermediateOutput(characteristic.OutputDifference);
List <List <SubstitutionBoxOutput> > usedBoxes = new List <List <SubstitutionBoxOutput> >(characteristic.UsedSubstitutionBoxes);
usedBoxes.AddRange(e.UsedSubstitutionBoxes);
e.SetUsedSubstitionBoxes(usedBoxes);
});
List <DifferentialCharacteristic> permutatedOutcomes = GetPermutatedOutcomes(possibleOutcomes);
return(permutatedOutcomes);
}
private List <DifferentialCharacteristic> GetCharacteristicsForSPN(int inputDifference)
{
List <DifferentialCharacteristic> inputCharacteristics = new List <DifferentialCharacteristic>()
{
new DifferentialCharacteristic(inputDifference, inputDifference, 1)
};
for (int r = 1; r < _spn.RoundCount; r++)
{
for (int i = inputCharacteristics.Count - 1; i >= 0; i--)
{
DifferentialCharacteristic inputCharacteristic = inputCharacteristics[i];
inputCharacteristics.RemoveAt(i);
List <DifferentialCharacteristic> outputCharacteristics = GetCharacteristicForRound(inputCharacteristic);
inputCharacteristics.AddRange(outputCharacteristics);
}
}
return(inputCharacteristics);
}
