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Add additional jumbling-up in feistel rounds

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Leonetienne 2022-05-26 02:44:22 +02:00
parent bc3dae96a3
commit 101a1e0fd6
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GPG Key ID: C33879CD92E9708C
2 changed files with 37 additions and 13 deletions
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2
GCryptLib/include/GCrypt/Feistel.h
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@ -32,7 +32,7 @@ namespace Leonetienne::GCrypt {
private: private:
//! Will run the feistel rounds, with either regular key //! Will run the feistel rounds, with either regular key
//! order or reversed key order //! order or reversed key order
Block Run(const Block& data, bool reverseKeys); Block Run(const Block& data, bool modeEncrypt);
//! Arbitrary cipher function //! Arbitrary cipher function
static Halfblock F(Halfblock m, const Key& key); static Halfblock F(Halfblock m, const Key& key);

48
GCryptLib/src/Feistel.cpp
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@ -30,7 +30,7 @@ namespace Leonetienne::GCrypt {
return Run(data, true); return Run(data, true);
} }
Block Feistel::Run(const Block& data, bool reverseKeys) { Block Feistel::Run(const Block& data, bool modeEncrypt) {
const auto splitData = FeistelSplit(data); const auto splitData = FeistelSplit(data);
Halfblock l = splitData.first; Halfblock l = splitData.first;
Halfblock r = splitData.second; Halfblock r = splitData.second;
@ -38,19 +38,43 @@ namespace Leonetienne::GCrypt {
Halfblock tmp; Halfblock tmp;
for (std::size_t i = 0; i < N_ROUNDS; i++) { for (std::size_t i = 0; i < N_ROUNDS; i++) {
// Calculate key index
std::size_t keyIndex; // Encryption
if (reverseKeys) { if (modeEncrypt) {
keyIndex = N_ROUNDS - i - 1; const std::size_t keyIndex = i;
}
else { // Do a feistel round
keyIndex = i; tmp = r;
r = l ^ F(r, roundKeys[keyIndex]);
l = tmp;
// Jumble it up a bit more
l.ShiftRowsUpInplace();
l.ShiftCellsRightInplace();
l.ShiftBitsLeftInplace();
l.ShiftColumnsLeftInplace();
// Seal all these operations with a key
l += ReductionFunction(roundKeys[keyIndex]);
}
// Decryption
else {
// Decryption needs keys in reverse order
const std::size_t keyIndex = N_ROUNDS - i - 1;
// Unjumble the jumble
r -= ReductionFunction(roundKeys[keyIndex]);
r.ShiftColumnsRightInplace();
r.ShiftBitsRightInplace();
r.ShiftCellsLeftInplace();
r.ShiftRowsDownInplace();
// Do a feistel round
tmp = r;
r = l ^ F(r, roundKeys[keyIndex]);
l = tmp;
} }
// Do a feistel round
tmp = r;
r = l ^ F(r, roundKeys[keyIndex]);
l = tmp;
} }
// Block has finished de*ciphering. // Block has finished de*ciphering.