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#include <byte.h>
/* If you need to compare a password or a hash value, the timing of the
* comparison function can give valuable clues to the attacker. Let's
* say the password is 123456 and the attacker tries abcdef. If the
* comparision function fails at the first byte without looking at the
* other bytes, then the attacker can measure the difference in runtime
* and deduce which byte was wrong, reducing the attack space from
* exponential to polynomial. */
int byte_equal_notimingattack(const void* a, size_t len,const void* b) {
size_t i;
const unsigned char* x=(const unsigned char*)a;
const unsigned char* y=(const unsigned char*)b;
unsigned char res=0;
for (i=0; i<len; ++i) {
res |= (x[i]^y[i]);
return res==0;