hmac_sha1(9)

💅 hmac_sha1 — the Kernel API Manual edition 🎀

okay so bestie, welcome to hmac_sha1(9) — yes that's the page name, yes it's from the Kernel API Manual, and yes we're gonna get through this together ✨

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🌸 NAME 🌸

hmac_sha1 — compute HMAC-SHA1 in one shot, using a prepared key. literally one call, no drama, we love a one-shot queen 👑

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✨ SYNOPSIS ✨

void hmac_sha1 (const struct hmac_sha1_key *key , const u8 *data ,
size_t data_len , u8 out[static SHA1_DIGEST_SIZE] );

that's it. that's the whole vibe check 🫶

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🦋 ARGUMENTS 🦋

• key — the prepared HMAC key 💖 like, it's already been prepped, don't come at it raw (iykyk — see DESCRIPTION)
• data — the message data 🌈 the actual content you're HMAC-ing, the main character
• data_len — the data length in bytes 📏 gotta know how much data you're feeding in, no cap
• out — (output) the resulting HMAC-SHA1 value 🎀 this is where the magic lands, it's the output param, it writes into here

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💜 DESCRIPTION 💜

so here's the tea: if you're using the key only once, consider using hmac_sha1_usingrawkey instead 💅 that's the whole description. short and iconic. periodt.

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🔥 CONTEXT 🔥

Any context. ✨ literally any. she's flexible, she doesn't gatekeep 🌸

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👑 SEE ALSO 👑

go read these next, bestie, they're all in the kernel file ./include/crypto/sha1.h 📂:

• struct sha1_ctx(9)
• sha1_init(9)
• sha1_update(9)
• sha1_final(9)
• sha1(9)
• struct hmac_sha1_key(9)
• struct hmac_sha1_ctx(9)
• hmac_sha1_preparekey(9)
• hmac_sha1_init(9)
• hmac_sha1_init_usingrawkey(9)
• hmac_sha1_update(9)
• hmac_sha1_final(9)
• hmac_sha1_usingrawkey(9)

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💀 reminder bestie: if that key is a one-time thing, hmac_sha1_usingrawkey is right there. don't make it complicated 🙈

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and that's the page!! source is ./include/crypto, dated October 2026 ⭐ mwah, you ate this, go forth and HMAC responsibly 💖🧚‍♀️