utilities.cpp

#include "utilities.h"

//this function computes the Hamming Distance between two strings of bits of size a.size()
int hammingDistance(string &a, string &b) {

	int out = 0;

	for(int i = 0; i < a.size(); i++) {
		if(a[i] != b[i]) {
			out++;
		}
	}
	return out;
}
//this function returns the 3 key_sizes with the smallest hamming distances as pos[]
void find_shortest_distances(string &bin_text, int pos[]) {

	vector <float> distance;
	for(int i = 2; i <= 40; i++) {

		string foo = "";
		string bar = "";

		for(int j = 0; j < i * 8; j++) {

			foo += bin_text[j];
		}
		for(int j = i*8; j < (i*8)*2; j++) {
			bar += bin_text[j];
		}
		float temp = hammingDistance(foo,bar);
		temp = temp /i;

		distance.push_back(temp);
	}
	float temp = 10000;

	for(int i = 0; i < distance.size(); i++) {
		if(distance[i] < temp) {
			temp = distance[i];
			pos[0] = i;
		}
	}
	temp = 10000;
	for(int i = 0; i < distance.size(); i++) {
		if(distance[i] != distance[pos[0]]) {
			if(distance[i] < temp) {
				temp = distance[i];
				pos[1] = i;
			}
		}
	}
	cout << "\n";
	temp = 10000;
	for(int i = 0; i < distance.size(); i++) {
		if(distance[i] != distance[pos[0]]) {
			if(distance[i] != distance[pos[1]]) {
				if(distance[i] < temp) {
					temp = distance[i];
					pos[2] = i;
				}
			}
		}
	}
	cout << "output: " << pos[0] << " : " << distance[pos[0]] << " " << pos[1] << " : "  << distance[pos[1]] << " " << pos[2] << " : " << distance[pos[2]] << "\n";
	for(int i = 0; i < 3; i++) {
		for(int j = 0; j < pos[i]; j++) {
			
		}
	}
}

// breaks ciphertext into blocks of keysize, stores in a vector of strings
vector <string> breakIntoBlocks(int &keysize, string &ciphertext) {
	vector <string> output;

	int i = 0;

	while(i < ciphertext.size()) {
			string temp = "";
		for(int j = 0; j < keysize*8; j++) {
			temp += ciphertext[i];
			i++;
		}
		output.push_back(temp);
	}

	return output;
}
//transposes a vector of strings
vector <string> transpose(vector <string> &input) {

	vector <string> output;

	int temp = 0;

	while(temp < input[0].size()) {
		string foo = "";
		for(int i = 0; i < input.size(); i++) {

			foo += input[i][temp];
				
		}
		output.push_back(foo);
		temp++;
	}
	return output;
}


//this function converts a single character to it's binary form, stored in a string.
string ctobin(char &c) {

	string bar = "";
	//typecast ascii to int
	int foo = (int)c;

	//cout << "c: " << c << "cast to int: " << foo << "\n";
	//this while loop find's the ones
	while(foo != 0) {

		if(foo % 2 == 1) {
			bar += "1";
		}
		else {
			bar += "0";
		}
		foo = foo/2;
	}
	//this while loop fills in zeros and make's sure the ascii character is represented as a byte
	while(bar.size() < 8) {

		bar += "0";
	}
	//reverse the string to be returned, since it's in reverse order.
	reverse(bar.begin(),bar.end());

	return bar;
}

//this function converts a 8 character string of '0''s and '1''s to the ascii equivalent
char bintoc(string &input) {

	int sum = 0;

	for(int i = 0; i < 8; i++) {

		if(input[i] == '1') {
			sum += pow(2,7-i);
		}
	}
	return (char)sum;
}
//converts a 4 bit string to it's hex equivalent
char bintohex(string &input) {

	if (input == "0000")return '0';
		
	else if(input=="0001") return '1';

	else if(input=="0010") return '2';

	else if(input=="0011") return '3';

	else if(input=="0100") return '4';

	else if(input=="0101") return '5';

	else if(input=="0110") return '6';

	else if(input=="0111") return '7';

	else if(input=="1000") return '8';

	else if(input=="1001") return '9';

	else if(input=="1010") return 'a';

	else if(input=="1011") return 'b';

	else if(input=="1100") return 'c';

	else if(input=="1101") return 'd';

	else if(input=="1110") return 'e';

	else return 'f';
	
}

//converts an int to byte form represented as a string
string dectobin(int foo) {

string bar = "";

while(foo != 0) {

		if(foo % 2 == 1) {
			bar += "1";
		}
		else {
			bar += "0";
		}
		foo = foo/2;
	}
	//this while loop fills in zeros and make's sure the int is represented as a byte
	while(bar.size() < 8) {

		bar += "0";
	}
	//reverse the string to be returned, since it's in reverse order.
	reverse(bar.begin(),bar.end());

	return bar;
}

//takes in a hexadecimal character and converts it to it's binary representation
string hextobin(char &input) {
	
	switch(input) {

		case '0' :
			return "0000";
		case '1' :
			return "0001";
		case '2' :
			return "0010";
		case '3' :
			return "0011";
		case '4' :
			return "0100";
		case '5' :
			return "0101";
		case '6' :
			return "0110";
		case '7' :
			return "0111";
		case '8' :
			return "1000";
		case '9' :
			return "1001";
		case 'a' :
			return "1010";
		case 'b' :
			return "1011";
		case 'c' :
			return "1100";
		case 'd' :
			return "1101";
		case 'e' :
			return "1110";
		case 'f' :
			return "1111";
	}
	return NULL;
}

//takes in any number of bits represented as a string, returns it's decimal equivalent as an int 
//used for bintob64
int bitstodec(string &input) {

	int sum = 0;

	for(int i = 0; i < input.size(); i++) {

		if(input[i] == '1') {
			sum += pow(2,input.size()-1-i);
		}
	}
	return sum;
}