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

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;