cryptosystem.cpp

des preko c neznam hocel pomoci

/* cryptosystem.cpp */
/* Apstraktna klasa kriptosustava. */
/* 2004. godina */
/* Autor: Darko Poljak */

/* za objasnjenje f-ja vidjeti header */

#include "cryptosystem.h"
#include <ctype.h>

string CryptoSystem::toHexString(const string& text) {
	string result;
	for(uint i=0;i<text.length();++i) {
		uint16 c=(unsigned char)text[i];
		result+=CONVERT_DEC_HEX[(c>>4)&0xF];
		result+=CONVERT_DEC_HEX[c&0xF];
	}
	return result;
}

string CryptoSystem::toBinaryString(const string& text) {
	string result;

	for(uint i=0;i<text.length();++i) {
		uint8 ch=(unsigned char)text[i];
		for(int j=7;j>=0;--j) {
			result+=(unsigned char)((ch>>j)&0x1)+'0';
		}
	}
	return result;
}

int CryptoSystem::hexDigitNumber(const char hex) {
	int result=-1;

	if(isdigit(hex)) {
		result=hex-'0';
	} else if((hex>='A' && hex<='F') ||
				(hex>='a' && hex<='f')) {
		result=toupper(hex)-'A'+10;
	}
	return result;
}

string CryptoSystem::hexToAscii(const string& hex) {
	string result;
	int n;
	int digit,len=hex.length();

	for(int i=len-1;i>=len%2;i-=2) {
		digit=hexDigitNumber(hex[i]);
		if(digit<0) {
			throw string("Invalid hex digit!");
		}
		n=digit;
		digit=hexDigitNumber(hex[i-1]);
		if(digit<0) {
			throw string("Invalid hex digit!");
		}
		n+=digit*16;
		string s;
		s+=(char)n;
		result.insert(0,s);
	}
	if(len%2) {
		n=hexDigitNumber(hex[0]);
		if(n<0) {
			throw string("Invalid hex digit!");
		}
		string s;
		s+=(char)n;
		result.insert(0,s);
	}
	return result;
}

string CryptoSystem::binToAscii(const string& bin) {
	int len=bin.length();
	string result;
	uint8 num;

	for(int i=1;i<=len/8;++i) {
		num=0;
		for(int j=0;j<8;++j) {
			uint8 digit=bin[len-i*8+j];
			if(digit!='0' && digit!='1') {
				throw string("Invalid binary digit!");
			}
			num<<=1;
			num|=digit-'0';
		}
		string s;
		s+=(char)num;
		result.insert(0,s);
	}
	len%=8;
	if(len!=0) {
		num=0;
		for(int i=0;i<len;++i) {
			uint8 digit=bin[i];
			if(digit!='0' && digit!='1') {
				throw string("Invalid binary digit!");
			}
			num<<=1;
			num|=digit-'0';
		}
		string s;
		s+=(char)num;
		result.insert(0,s);
	}
	return result;
}