hmac_sha256_usingrawkey(9)

📦 version 7.3.1, in nixpkgs unstable

💅 hmac_sha256_usingrawkey — Kernel API Manual, section 9 🎀

okay so picture this: you're in kernel land (yes, the kernel, we're fancy now ✨), and you need one single HMAC-SHA256. Not a whole session. Not a whole state machine. Just one. And you've got the raw key sitting right there in your hand like 🫶. That's this function, bestie. It does the whole thing in one shot, no cap.

🌸 NAME 🌸

hmac_sha256_usingrawkey — Compute HMAC-SHA256 in one shot, using a raw key 💖

✨ SYNOPSIS ✨

void hmac_sha256_usingrawkey (const u8 *raw_key , size_t raw_key_len ,
       const u8 *data , size_t data_len , u8 out[static SHA256_DIGEST_SIZE] );

like, five args, zero drama. she's an icon, she's a legend, and she is the moment 👑

🦋 ARGUMENTS 🦋

  • raw_key — the raw HMAC-SHA256 key itself. just... the key. raw. unprocessed. the real deal 🙈
  • raw_key_len — the key length in bytes. and listen — All key lengths are supported. every single one. no cap, no restrictions, she does not gatekeep 🔥
  • data — the message data 📩
  • data_len — the data length in bytes
  • out — (output) the resulting HMAC-SHA256 value. this is where the magic lands, bestie 💫

💜 DESCRIPTION 💜

So like, the actual vibe here is minimal because the function is minimal. But here's the one thing you need to know, and it's giving "listen to me for two seconds":

If you're using the key multiple times, prefer to use hmac_sha256_preparekey followed by multiple calls to hmac_sha256 instead. 🔁

fr fr. one-shot is for one shot. if you're looping, prep the key once and reuse it — that's the whole point. don't be out here re-deriving a key forty times in a loop, it's not the move 💀

🌈 CONTEXT 🌈

Any context. literally any. no constraints, no prerequisites, no special preemption rules. she's flexible like that 🧚

👑 SEE ALSO 👑

the whole sha2 extended universe, in the exact order the kernel lists it — iykyk 🌟

Kernel file ./include/crypto/sha2.h and friends:

🎀 and that's the page!! tysm for reading, you ate that 💅

signed, sealed, and shipped from ./include/crypto, dated October 2026 — Kernel API Manual, hmac_sha256_usingrawkey(9) ⭐🦋💜

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