KCAPI_HKDF(3)

📦
version 1.5.0 · 7 versions
, in fedora 43

✨ NAME ✨

kcapi_hkdf — Extract-and-Expand HKDF (RFC5869)

okay bestie, welcome to page 3 of the libkcapi manual — this is KCAPI_HKDF(3) and it's literally the glow-up your key derivation needed 💅

🎀 SYNOPSIS 🎀

ssize_t kcapi_hkdf(const char * hashname, const uint8_t * ikm,
                   size_t ikmlen, const uint8_t * salt,
                   uint32_t saltlen, const uint8_t * info,
                   size_t infolen, uint8_t * dst, size_t dlen);

🦋 ARGUMENTS 🦋

  • hashname — [in] the kernel crypto API name of a keyed hash, like hmac(sha1). that's the flavor of hash you're serving today 🍓
  • ikm — [in] Input Keying Material (IKM) — and no, you can't skip it, it must be provided. it's the main character here 👑
  • ikmlen — [in] the length of the IKM buffer — must be non-zero. we do not accept zero, periodt
  • salt — [in] salt buffer — lowkey optional, it may be NULL 🧂
  • saltlen — [in] salt buffer length — may be zero
  • info — [in] info buffer — also chill, may be NULL
  • infolen — [in] info buffer length — may be zero
  • dst — [out] Buffer to store the generated key in,
  • dlen — [in] Length of the dst buffer. This value defines the number of bytes generated by the KDF. so like, this is you deciding how much key you want ✨

💖 DESCRIPTION 💖

Perform the key-derivation function according to RFC5869. The input data is defined in sections 2.2 und 2.3 of RFC5869. (yes the "und" is in the original, we keep the receipts, no cap 🫶)

return 0 upon success; a negative errno-style error code if an error occurred. so zero = slay, negative = something went sideways 😭

🌸 AUTHOR 🌸

Stephan Mueller <smueller@chronox.de>

  • Author.
that's the whole page bestie, go forth and derive 💜

and finally, the cute lil sign-off: this page comes from the libkcapi Manual 1.5.0, dated July 2025. bye bestie, drink water, check your error codes 💅🦋✨

📦 where this page comes from