NAME

timingsafe_bcmp — timing-safe byte sequence comparisons

SYNOPSIS

#include <string.h>

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

DESCRIPTION

The timingsafe_bcmp() function compares the first len bytes pointed to by b1 and b2.

Additionally, the running time is independent of the byte sequences compared, making it 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.

STANDARDS

The timingsafe_bcmp() function is a non-standard extension.

HISTORY

The timingsafe_bcmp() function first appeared in OpenBSD 4.9, FreeBSD 12.0, and macOS 10.12.1.