cryptography-utils/brute.cc

#include <iostream>

void shift(char* text, int key)
{
	std::cout << key << ": ";
	for(int i = 0; text[i] != 0; ++i)
	{
		if(text[i] == ' ')
		{
			std::cout << ' ';
			continue;
		}
		// has to be int, because the result can sometimes be > 127
		int c = std::tolower(text[i])-key;
		if(c < 'a') c+=26;
		if(c > 'z') c-=26;
		std::cout << (char)c;
	}
	std::cout << std::endl;
}
int main(int argc, char** argv)
{
	if(argc < 2)
	{
		std::cout << "Usage: " << argv[0] << " <ciphertext>" << std::endl;
		return 0;
	}
	for(int i = 1; i < 26; ++i)
	{
		shift(argv[1], i);
	}
	return 0;
}