BCMP(3) OpenBSD Programmer's Manual BCMP(3)NAME
bcmp, timingsafe_bcmp - compare byte string
SYNOPSIS
#include <string.h>
int
bcmp(const void *b1, const void *b2, size_t len);
int
timingsafe_bcmp(const void *b1, const void *b2, size_t len);
DESCRIPTION
The bcmp() function compares byte string b1 against byte string b2,
returning zero if they are identical, non-zero otherwise. Both strings
are assumed to be len bytes long. Zero-length strings are always
identical.
The strings may overlap.
The timingsafe_bcmp() function has the same semantics as bcmp(), but its
running time is independent of the contents of b1 and b2, making it safe
to use for comparing secret values such as cryptographic MACs. In
contrast, bcmp() returns after finding the first differing byte, making
it vulnerable to timing attacks.
SEE ALSOmemcmp(3), strcasecmp(3), strcmp(3), strcoll(3), strxfrm(3)HISTORY
A bcmp() function first appeared in 4.2BSD.
The timingsafe_bcmp() function first appeared in OpenBSD 4.9.
OpenBSD 4.9 September 24, 2010 OpenBSD 4.9
