TIMINGSAFE_BCMP(3)     FreeBSD Library Functions Manual     TIMINGSAFE_BCMP(3)

NAME
     timingsafe_bcmp, timingsafe_memcmp - timing-safe byte sequence
     comparisons

SYNOPSIS
     #include <string.h>

     int
     timingsafe_bcmp(const void *b1, const void *b2, size_t len);

     int
     timingsafe_memcmp(const void *b1, const void *b2, size_t len);

DESCRIPTION
     The timingsafe_bcmp() and timingsafe_memcmp() functions lexicographically
     compare the first len bytes (each interpreted as an unsigned char)
     pointed to by b1 and b2.

     Additionally, their running times are independent of the byte sequences
     compared, making them safe to use for comparing secret values such as
     cryptographic MACs.  In contrast, bcmp(3) and memcmp(3) may short-circuit
     after finding the first differing byte.

RETURN VALUES
     The timingsafe_bcmp() function returns 0 or not zero if the byte sequence
     pointed to by b1 compares equal to or not equal to (respectively) the
     byte sequence pointed to by b2.

     The timingsafe_memcmp() function returns a negative value, 0, or positive
     value if the byte sequence pointed to by b1 compares less than, equal to,
     or greater than (respectively) the byte sequence pointed to by b2.

SEE ALSO
     bcmp(3), memcmp(3)

STANDARDS
     The timingsafe_bcmp() and timingsafe_memcmp() functions are FreeBSD
     extensions.

HISTORY
     The timingsafe_bcmp() function first appeared in OpenBSD 4.9.

     The timingsafe_memcmp() function first appeared in OpenBSD 5.6.

     Both functions first appeared in FreeBSD 12.0.

FreeBSD 13.1-RELEASE-p6         August 15, 2016        FreeBSD 13.1-RELEASE-p6