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Automatically generating round keyset

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Leonetienne 2021-12-05 17:09:01 +01:00
parent dd8942ed1c
commit 5c73a3b35e
1 changed files with 34 additions and 18 deletions
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52
main.cpp
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@ -5,10 +5,11 @@
#define BLOCK_SIZE 128 #define BLOCK_SIZE 128
#define FEISTELBLOCK_SIZE (BLOCK_SIZE / 2) #define FEISTELBLOCK_SIZE (BLOCK_SIZE / 2)
#define N_ROUNDS 8 #define N_ROUNDS 64
typedef std::bitset<BLOCK_SIZE> Block; typedef std::bitset<BLOCK_SIZE> Block;
typedef std::bitset<FEISTELBLOCK_SIZE> Feistelblock; typedef std::bitset<FEISTELBLOCK_SIZE> Feistelblock;
typedef std::array<Feistelblock, N_ROUNDS> Keyset;
// Will convert a string to a data block // Will convert a string to a data block
Block StringToBits(const std::string& s); Block StringToBits(const std::string& s);
@ -22,37 +23,37 @@ std::pair<Feistelblock, Feistelblock> FeistelSplit(const Block& block);
// Combine two feistel blocks (L and R) into a regular data block // Combine two feistel blocks (L and R) into a regular data block
Block FeistelCombine(const Feistelblock& l, const Feistelblock& r); Block FeistelCombine(const Feistelblock& l, const Feistelblock& r);
// Will generate a keyset from a seed-key
Keyset GenerateRoundkeys(const Feistelblock& seedKey);
// Feistel-cipher // Feistel-cipher
Block Feistel(const Block& data, const std::array<Feistelblock, 8>& keys, bool reverseKeyOrder = false); Block Feistel(const Block& data, const Keyset& keys, bool reverseKeyOrder = false);
// Arbitrary cipher function // Arbitrary cipher function
Feistelblock F(Feistelblock m, const Feistelblock& key); Feistelblock F(Feistelblock m, const Feistelblock& key);
int main() int main()
{ {
const std::string asciiMessage = "Hello, World! :3"; const std::string asciiMessage = "Guten Abend!";
Block message = StringToBits(asciiMessage); Block message = StringToBits(asciiMessage);
const std::array<Feistelblock, N_ROUNDS> keys = { const Feistelblock seedKey(StringToBits("Ich bin ein PASSWORT-SCHLÜSSEL!").to_string()); // StringToBits returns a bitset that's too large. We have to trim it to fit the smaller FeistelBlock bitset.
0b11101101, const Keyset roundkeys = GenerateRoundkeys(seedKey);
0b01110101,
0b10111101, //std::cout << "Keys: " << std::endl;
0b00010110, //for (std::size_t i = 0; i < roundkeys.size(); i++)
0b00000011, // std::cout << roundkeys[i] << std::endl;
0b10110011, //std::cout << "---" << std::endl;
0b11011101,
0b00111101
};
std::cout << "Message ascii: " << asciiMessage << std::endl; std::cout << "Message ascii: " << asciiMessage << std::endl;
std::cout << "Message: " << message << std::endl; std::cout << "Message: " << message << std::endl;
Block ciphertext = Feistel(message, keys); Block ciphertext = Feistel(message, roundkeys);
std::cout << "Ciphertext: " << ciphertext << std::endl; std::cout << "Ciphertext: " << ciphertext << std::endl;
Block decrypted = Feistel(ciphertext, keys, true); Block decrypted = Feistel(ciphertext, roundkeys, true);
std::cout << "Decrypted: " << decrypted << std::endl; std::cout << "Decrypted: " << decrypted << std::endl;
const std::string asciiDecrypted = BitsToString(decrypted); const std::string asciiDecrypted = BitsToString(decrypted);
@ -61,7 +62,7 @@ int main()
return 0; return 0;
} }
Block Feistel(const Block& data, const std::array<Feistelblock, 8>& keys, bool reverseKeyOrder) Block Feistel(const Block& data, const Keyset& keys, bool reverseKeyOrder)
{ {
const auto splitData = FeistelSplit(data); const auto splitData = FeistelSplit(data);
Feistelblock l = splitData.first; Feistelblock l = splitData.first;
@ -91,8 +92,10 @@ Feistelblock F(Feistelblock m, const Feistelblock& key)
{ {
// Made-up F function // Made-up F function
// Shift 5 to the left // Shift to left by 3 for every 1 in the key
m <<= 5; for (std::size_t i = 0; i < key.size(); i++)
if (key[i])
m <<= 3;
// Xor with key // Xor with key
return m ^ key; return m ^ key;
@ -140,3 +143,16 @@ Block FeistelCombine(const Feistelblock& l, const Feistelblock& r)
{ {
return Block(l.to_string() + r.to_string()); return Block(l.to_string() + r.to_string());
} }
Keyset GenerateRoundkeys(const Feistelblock& seedKey)
{
Keyset keys;
keys[0] = seedKey;
for (std::size_t i = 1; i < keys.size(); i++)
{
keys[i] = std::hash<Feistelblock>{}(keys[i-1]);
}
return keys;
}