Session Encrypter C++

// return an array with encrypted bytes
std::vector<std::string> encryptedBytes(int num)
{
	std::vector<std::string> temp;
	std::stringstream ss;
	for (int i = 0, j = 0; i <= num; i++)
	{
		if (i % 10 == 0 && i != 0)
		{
			ss << std::uppercase << std::hex << 83 + j + 6;
			j += 7;
		}
		else
		{
			ss << std::uppercase << std::hex << 83 + j;
			j++;
		}
		temp.push_back(ss.str());
		ss.str("");
	}
	return temp;
}

// encrypt session packet < identifier > < session >
std::string sessionEncrypt(std::string identifier, std::string session)
{
	std::vector<std::string> table = encryptedBytes(99);

	std::string str_enc;
	str_enc += 0x9A;

	std::stringstream ss;
	ss << identifier[0] << identifier[1];
	str_enc += toString(table[atoi(ss.str().c_str())]);
	ss.str("");
	ss << identifier[2] << identifier[3];
	str_enc += toString(table[atoi(ss.str().c_str())]);
	ss.str("");
	ss << identifier[4];
	
	switch (atoi(ss.str().c_str()))
	{
	case 0:
		str_enc += 0x50;
		break;
	case 1:
		str_enc += 0x60;
		break;
	case 2:
		str_enc += 0x70;
		break;
	case 3:
		str_enc += 0x80;
		break;
	case 4:
		str_enc += 0x90;
		break;
	case 5:
		str_enc += 0xA0;
		break;
	case 6:
		str_enc += 0xB0;
		break;
	case 7:
		str_enc += 0xC0;
		break;
	case 8:
		str_enc += 0xD0;
		break;
	case 9:
		str_enc += 0xE0;
		break;
	}

	ss.str("");
	ss << session[0] << session[1];
	str_enc += toString(table[atoi(ss.str().c_str())]);
	ss.str("");
	ss << session[2] << session[3];
	str_enc += toString(table[atoi(ss.str().c_str())]);
	ss.str("");
	ss << session[4];

	switch (atoi(ss.str().c_str()))
	{
	case 0:
		str_enc += 0x4F;
		break;
	case 1:
		str_enc += 0x5F;
		break;
	case 2:
		str_enc += 0x6F;
		break;
	case 3:
		str_enc += 0x7F;
		break;
	case 4:
		str_enc += 0x8F;
		break;
	case 5:
		str_enc += 0x9F;
		break;
	case 6:
		str_enc += 0xAF;
		break;
	case 7:
		str_enc += 0xBF;
		break;
	case 8:
		str_enc += 0xCF;
		break;
	case 9:
		str_enc += 0xDF;
		break;
	}

	ss.str("");

	return str_enc += 0x0E;
}

std::string toHex(std::string str)
{
	std::stringstream ss;
	for (unsigned int i = 0; i < str.size(); i++)
		ss << std::uppercase << std::hex << std::setw(2) << std::setfill('0') << (int)(unsigned char)str[i] << " ";
	return ss.str();
}

std::string toString(const std::string &input)
{
	static const char* const lut = "0123456789ABCDEF";
	size_t len = input.length();
	if (len & 1) throw std::invalid_argument("odd length");
	std::string output;
	output.reserve(len / 2);
	for (size_t i = 0; i < len; i += 2)
	{
		char a = input[i];
		const char* p = std::lower_bound(lut, lut + 16, a);
		if (*p != a) throw std::invalid_argument("not a hex digit");
		char b = input[i + 1];
		const char* q = std::lower_bound(lut, lut + 16, b);
		if (*q != b) throw std::invalid_argument("not a hex digit");
		output.push_back(((p - lut) << 4) | (q - lut));
	}
	return output;
}

sessionEncrypt("53061", "26705")