TIMINGSAFE_BCMP(3)

🦋 timingsafe_bcmp(3) & timingsafe_memcmp(3) — Library Functions Manual 🦋

🎀 NAME 🎀

timingsafe_bcmp, timingsafe_memcmp — timing-safe byte sequence comparisons. okay bestie, that's the whole assignment: compare bytes without leaking timing tea ☕✨

✨ SYNOPSIS ✨

okay so first you literally include this:

#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 💖

okay so timingsafe_bcmp() and timingsafe_memcmp() lexicographically compare the first len bytes (each interpreted as an unsigned char) pointed to by b1 and b2. the way that's so specific and so iconic ✨

and the main-character part? their running times are independent of the byte sequences compared, making them safe to use for comparing secret values such as cryptographic MACs. that's the whole point, bestie 🫶

in contrast, bcmp(3) and memcmp(3) may short-circuit after finding the first differing byte — which is giving leaky timing energy 💀🙈

🫶 RETURN VALUES 🫶

• timingsafe_bcmp() — returns 0 if the byte sequence pointed to by b1 compares equal to the byte sequence pointed to by b2, or not zero if it compares not equal. respectively, no cap ✨
• timingsafe_memcmp() — returns a negative value if the byte sequence pointed to by b1 compares less than the byte sequence pointed to by b2, 0 if it compares equal, or a positive value if it compares greater. again, respectively 💅

🌈 SEE ALSO 🌈

• bcmp(3)
• memcmp(3)

👑 STANDARDS 👑

timingsafe_bcmp() and timingsafe_memcmp() are FreeBSD extensions. periodt. 👑

🕰️ HISTORY 🕰️

• timingsafe_bcmp() first appeared in OpenBSD 4.9.
• timingsafe_memcmp() first appeared in OpenBSD 5.6.
• both functions first appeared in FreeBSD 11.1.

xoxo, your Debian bestie 💌 — this cutie is dated August 15, 2016, and it's the TIMINGSAFE_BCMP(3) manual page. slay and stay timing-safe 💅✨