timingsafe_memcmp.c File Reference

#include "safe_mem_lib.h"

Include dependency graph for timingsafe_memcmp.c:

Functions
EXPORT int	timingsafe_memcmp (const void *b1, const void *b2, size_t len)
	Compare all memory bytes. More...

Function Documentation

timingsafe_memcmp()

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

Compare all memory bytes.

Return their difference sign (-1,0,1).

The running time is 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.

Remarks

from OpenBSD

Parameters

b1	pointer to memory to compare against
b2	pointer to the source memory to compare with b1
len	number of bytes to compare in both buffers

Precondition

Neither b1 nor b2 shall be a null pointer.

Return values

-1,0,or

1

See also

memcmp_s(), timingsafe_bcmp()