Added a FeistelManager to en/decipher arbitrarily long messages using cipher block chaining

Feistel.cpp

@@ -21,17 +21,17 @@ void Feistel::SetKey(const Block& key)
     return;
 }
 
-Block Feistel::Encipher(const Block& data)
+Block Feistel::Encipher(const Block& data) const
 {
     return Run(data, false);
 }
 
-Block Feistel::Decipher(const Block& data)
+Block Feistel::Decipher(const Block& data) const
 {
     return Run(data, true);
 }
 
-Block Feistel::Run(const Block& data, bool reverseKeys)
+Block Feistel::Run(const Block& data, bool reverseKeys) const
 {
     const auto splitData = FeistelSplit(data);
     Halfblock l = splitData.first;
@@ -173,6 +173,8 @@ std::string Feistel::SBox(const std::string& in)
 
 void Feistel::GenerateRoundKeys(const Block& seedKey)
 {
+    // Generate round keys via output feedback modus (OFM) method
+
     // Clear initial key memory
     ZeroKeyMemory();
     roundKeys = Keyset();

Feistel.h

@@ -8,7 +8,11 @@
 class Feistel
 {
 public:
-	Feistel(const Block& key);
+	explicit Feistel(const Block& key);
+
+	Feistel(const Feistel& other) = delete;
+	Feistel(Feistel&& other) noexcept = delete;
+
 	~Feistel();
 
 	//! Will set the seed-key for this feistel network.
@@ -16,14 +20,14 @@ public:
 	void SetKey(const Block& key);
 
 	//! Will encipher a data block via the set seed-key
-	Block Encipher(const Block& data);
+	Block Encipher(const Block& data) const;
 
 	//! Will decipher a data block via the set seed-key
-	Block Decipher(const Block& data);
+	Block Decipher(const Block& data) const;
 
 private:
 	//! Will run the feistel rounds, with either regular key order or reversed key order
-	Block Run(const Block& data, bool reverseKeys);
+	Block Run(const Block& data, bool reverseKeys) const;
 
 	//! Arbitrary cipher function
 	static Halfblock F(Halfblock m, const Block& key);

Feistel.vcxproj

@@ -146,12 +146,15 @@
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Release|x64'">true</ExcludedFromBuild>
     </ClCompile>
     <ClCompile Include="Feistel.cpp" />
+    <ClCompile Include="FeistelMan.cpp" />
     <ClCompile Include="main.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="Block.h" />
     <ClInclude Include="Config.h" />
     <ClInclude Include="Feistel.h" />
+    <ClInclude Include="FeistelMan.h" />
+    <ClInclude Include="Flexblock.h" />
     <ClInclude Include="Halfblock.h" />
     <ClInclude Include="Keyset.h" />
     <ClInclude Include="Util.h" />

Feistel.vcxproj.filters

@@ -24,6 +24,9 @@
     <ClCompile Include="main.cpp">
       <Filter>Quelldateien</Filter>
     </ClCompile>
+    <ClCompile Include="FeistelMan.cpp">
+      <Filter>Quelldateien</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="Feistel.h">
@@ -44,5 +47,11 @@
     <ClInclude Include="Util.h">
       <Filter>Headerdateien</Filter>
     </ClInclude>
+    <ClInclude Include="FeistelMan.h">
+      <Filter>Headerdateien</Filter>
+    </ClInclude>
+    <ClInclude Include="Flexblock.h">
+      <Filter>Headerdateien</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

FeistelMan.cpp

@@ -0,0 +1,114 @@
+#include "FeistelMan.h"
+#include "Util.h"
+#include <iostream>
+
+FeistelMan::FeistelMan(const Block& key)
+	:
+	key { key }
+{
+
+	return;
+}
+
+FeistelMan::FeistelMan(const std::string& password)
+{
+	key = PasswordToKey(password);
+
+	return;
+}
+
+FeistelMan::~FeistelMan()
+{
+	// Clear key memory
+	ZeroKeyMemory();
+
+	return;
+}
+
+void FeistelMan::SetKey(const Block& key)
+{
+	ZeroKeyMemory();
+
+	this->key = key;
+	return;
+}
+
+void FeistelMan::SetPassword(const std::string& password)
+{
+	ZeroKeyMemory();
+
+	key = PasswordToKey(password);
+	return;
+}
+
+Flexblock FeistelMan::Encipher(const Flexblock& data) const
+{
+	// Split cleartext into blocks
+	std::vector<Block> blocks;
+
+	for (std::size_t i = 0; i < data.size(); i += BLOCK_SIZE)
+		blocks.push_back(Block(
+			PadStringToLength(data.substr(i, BLOCK_SIZE), BLOCK_SIZE, '0', false))
+		);
+
+	// Encrypt individual blocks using cipher block chaining
+	Feistel feistel(key);
+
+	for (std::size_t i = 0; i < blocks.size(); i++)
+	{
+		const Block& lastBlock = (i>0) ? blocks[i-1] : emptyBlock;
+		blocks[i] = feistel.Encipher(blocks[i] ^ lastBlock);
+	}
+
+	// Concatenate ciphertext blocks back into a flexblock
+	std::stringstream ss;
+	for (Block& b : blocks)
+		ss << b;
+
+	// Return it
+	return ss.str();
+}
+
+Flexblock FeistelMan::Decipher(const Flexblock& data) const
+{
+	// Split ciphertext into blocks
+	std::vector<Block> blocks;
+
+	for (std::size_t i = 0; i < data.size(); i += BLOCK_SIZE)
+		blocks.push_back(Block(
+			PadStringToLength(data.substr(i, BLOCK_SIZE), BLOCK_SIZE, '0', false))
+		);
+
+	// Decrypt individual blocks
+	Feistel feistel(key);
+
+	// We can't do this in-loop for decryption, because we are decrypting the blocks in-place.
+	Block lastBlock = emptyBlock;
+	
+	for (std::size_t i = 0; i < blocks.size(); i++)
+	{
+		Block tmpCopy = blocks[i];
+
+		blocks[i] = feistel.Decipher(blocks[i]) ^ lastBlock;
+
+		lastBlock = std::move(tmpCopy);
+	}
+
+	// Concatenate ciphertext blocks back into a flexblock
+	std::stringstream ss;
+	for (Block& b : blocks)
+		ss << b;
+
+	// Return it
+	return ss.str();
+}
+
+#pragma optimize("", off )
+void FeistelMan::ZeroKeyMemory()
+{
+	key.reset();
+	return;
+}
+#pragma optimize("", on )
+
+const Block FeistelMan::emptyBlock;

FeistelMan.h

@@ -0,0 +1,38 @@
+#pragma once
+#include "Feistel.h"
+#include "Flexblock.h"
+
+/** Class to apply a block cipher to messages of arbitrary length in a distributed manner
+*/
+class FeistelMan
+{
+public:
+	explicit FeistelMan(const Block& key);
+	explicit FeistelMan(const std::string& password);
+
+	FeistelMan(const FeistelMan& other) = delete;
+	FeistelMan(FeistelMan&& other) noexcept = delete;
+	
+	~FeistelMan();
+
+	//! Will set the key
+	void SetKey(const Block& key);
+
+	//! Will set the key from a password
+	void SetPassword(const std::string& password);
+
+	//! Will encipher a flexblock of data
+	Flexblock Encipher(const Flexblock& data) const;
+
+	//! Will decipher a flexblock of data
+	Flexblock Decipher(const Flexblock& data) const;
+
+private:
+	Block key;
+
+	//! Will zero the memory used by the key
+	void ZeroKeyMemory();
+
+	// Initial value for cipher block chaining
+	static const Block emptyBlock;
+};

Flexblock.h

@@ -0,0 +1,5 @@
+#pragma once
+#include <vector>
+
+//! A "bitset" of variable length
+typedef std::string Flexblock;

main.cpp

@@ -1,10 +1,27 @@
 #pragma once
 #include <iostream>
 #include "Util.h"
-#include "Feistel.h"
+#include "FeistelMan.h"
 
 int main()
 {
+	FeistelMan feistel("Password yo");
+
+	const std::string message = "I am a veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeery long message!";
+
+	std::cout << "Cleartext: " << message << std::endl;
+
+	// Encrypt
+	const Flexblock ciphertext = feistel.Encipher(StringToBits(message));
+	const std::string cipherHex = BitsToHexstring(ciphertext);
+
+	std::cout << "Ciphertext: " << cipherHex << std::endl;
+
+
+	// Decrypt
+	const Flexblock cleartextBits = feistel.Decipher(HexstringToBits(cipherHex));
+	std::cout << "Decrypted:  " << BitsToString(cleartextBits) << std::endl;
+
 
 	return 0;
 }