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Now using full bitwidth keys

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Leonetienne 2021-12-05 18:47:42 +01:00
parent d6f47475ca
commit 1302fd38c6
1 changed files with 88 additions and 27 deletions
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85
main.cpp
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@ -9,7 +9,7 @@
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; typedef std::array<Block, 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);
@ -24,16 +24,22 @@ std::pair<Feistelblock, Feistelblock> FeistelSplit(const Block& 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 // Will generate a keyset from a seed-key
Keyset GenerateRoundkeys(const Feistelblock& seedKey); Keyset GenerateRoundkeys(const Block& seedKey);
// Feistel-cipher // Feistel-cipher
Block Feistel(const Block& data, const Keyset& keys, bool reverseKeyOrder = false); Block Feistel(const Block& data, const Keyset& keys, bool reverseKeyOrder = false);
// Will expand a halfblock to a fullblock
Block ExpansionFunction(const Feistelblock& block);
// Will compress a fullblock to a halfblock
Feistelblock CompressionFunction(const Block& block);
// Substitutes four bits by static random others // Substitutes four bits by static random others
std::string SBox(const std::string& in); std::string SBox(const std::string& in);
// Arbitrary cipher function // Arbitrary cipher function
Feistelblock F(Feistelblock m, const Feistelblock& key); Feistelblock F(Feistelblock m, const Block& key);
template<std::size_t T> template<std::size_t T>
std::bitset<T> Shiftl(const std::bitset<T>& bits, std::size_t amount); std::bitset<T> Shiftl(const std::bitset<T>& bits, std::size_t amount);
@ -71,14 +77,14 @@ std::string DebugPrint(const std::string& asciiMessage)
{ {
Block message = StringToBits(asciiMessage); Block message = StringToBits(asciiMessage);
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. const Block seedKey = StringToBits("Ich bin ein PASSWORT-SCHLÜSSEL!");
Keyset roundkeys = GenerateRoundkeys(seedKey); Keyset roundkeys = GenerateRoundkeys(seedKey);
//std::cout << "Keys: " << std::endl; //std::cout << "Keys: " << std::endl;
//for (std::size_t i = 0; i < roundkeys.size(); i++) //for (std::size_t i = 0; i < roundkeys.size(); i++)
// std::cout << roundkeys[i] << std::endl; // std::cout << roundkeys[i] << std::endl;
//std::cout << "---" << std::endl; //std::cout << "---" << std::endl;
//return 0; //exit(0);
std::cout << "Message ascii: " << asciiMessage << std::endl; std::cout << "Message ascii: " << asciiMessage << std::endl;
@ -123,28 +129,83 @@ Block Feistel(const Block& data, const Keyset& keys, bool reverseKeyOrder)
return FeistelCombine(r, l); return FeistelCombine(r, l);
} }
Feistelblock F(Feistelblock m, const Feistelblock& key) Feistelblock F(Feistelblock m, const Block& key)
{ {
// Made-up F function // Made-up F function
// Expand to full bitwidht
Block m_expanded = ExpansionFunction(m);
// Shift to left by 1 // Shift to left by 1
m = Shiftl(m, 1); m_expanded = Shiftl(m_expanded, 1);
// Xor with key // Xor with key
m ^= key; m_expanded ^= key;
// Non-linearly apply subsitution boxes // Non-linearly apply subsitution boxes
std::stringstream ss; std::stringstream ss;
const std::string m_str = m.to_string(); const std::string m_str = m_expanded.to_string();
for (std::size_t i = 0; i < m_str.size(); i += 4) for (std::size_t i = 0; i < m_str.size(); i += 4)
{ {
ss << SBox(m_str.substr(i, 4)); ss << SBox(m_str.substr(i, 4));
} }
m = Feistelblock(ss.str()); m_expanded = Block(ss.str());
return m; // Return the compressed version
return CompressionFunction(m_expanded);
}
Block ExpansionFunction(const Feistelblock& block)
{
std::stringstream ss;
const std::string bits = block.to_string();
// We have to double the bits!
for (std::size_t i = 0; i < bits.size(); i += 2)
{
const std::string sub = bits.substr(i, 2);
if (sub == "00") ss << "1101";
else if (sub == "01") ss << "1000";
else if (sub == "10") ss << "0010";
else /*if (sub == "11")*/ ss << "0111";
}
return Block(ss.str());
}
Feistelblock CompressionFunction(const Block& block)
{
std::stringstream ss;
const std::string bits = block.to_string();
// We have to double the bits!
for (std::size_t i = 0; i < bits.size(); i += 4)
{
const std::string sub = bits.substr(i, 4);
if (sub == "0000") ss << "10";
else if (sub == "0001") ss << "01";
else if (sub == "0010") ss << "10";
else if (sub == "0011") ss << "10";
else if (sub == "0100") ss << "11";
else if (sub == "0101") ss << "01";
else if (sub == "0110") ss << "00";
else if (sub == "0111") ss << "11";
else if (sub == "1000") ss << "01";
else if (sub == "1001") ss << "00";
else if (sub == "1010") ss << "11";
else if (sub == "1011") ss << "00";
else if (sub == "1100") ss << "11";
else if (sub == "1101") ss << "10";
else if (sub == "1110") ss << "00";
else /*if (sub == "1111")*/ ss << "01";
}
return Feistelblock(ss.str());
} }
std::string SBox(const std::string& in) std::string SBox(const std::string& in)
@ -210,7 +271,7 @@ 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 GenerateRoundkeys(const Block& seedKey)
{ {
Keyset keys; Keyset keys;