MatasanoCrypto/utils/xor.c

#include <string.h>

void xor_repeatedly(const unsigned char* const i_xor, const unsigned i_xor_len, const unsigned char* const i_string, const unsigned i_string_len, unsigned char* o_xored)
{
	unsigned counter = 0;
	while( counter < i_string_len )
	{
		unsigned xor_idx = counter % i_xor_len;
		o_xored[counter] = (i_string[counter]) ^ (i_xor[xor_idx]);
		counter++;
	}
}