polyval(9)

💅 polyval(9) — the one from the Kernel API Manual

okay so bestie, gather round, because today we're talking about polyval — and yes, that's the whole name, no notes. It computes a POLYVAL value. That's it. That's the function. Iconic, lowkey.

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✨ SYNOPSIS ✨

The whole vibe in one line, don't blink:

void polyval (const struct polyval_key *key , const u8 *data , size_t
len , u8 out[POLYVAL_BLOCK_SIZE] );

Like… it returns nothing (void, mysterious, main character energy) and it takes four things. Let's meet them 🫶

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🎀 ARGUMENTS 🎀

• key — the prepared key. Prepared!! As in already prepped, like she did her skincare routine before the party. Don't hand her a raw key, she's not doing that.
• data — the message data. The actual tea. The content. Give her the bytes.
• len — the length of the data, in bytes. And here's the slay part: it doesn't need to be block-aligned. Fr fr. Any length, she'll handle it, no padding gymnastics required from you 💅
• out — the output value. Where the answer goes. It's a u8 array of POLYVAL_BLOCK_SIZE, so it's a fixed-size situation — she writes into it, you don't get to negotiate the size.

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🦋 CONTEXT 🦋

Any context. Literally any. No locks, no "only in interrupt context", no "please call from a workqueue or she'll be moody". She's flexible like that. Vibe check: passed ✨

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🔥 SEE ALSO 🔥

The whole friend group, and yes I'm listing every single one because we do not do partial lists in this house:

• Kernel file ./include/crypto/gf128hash.h
• struct polyval_elem(9)
• struct ghash_key(9)
• struct polyval_key(9)
• struct ghash_ctx(9)
• struct polyval_ctx(9)
• ghash_preparekey(9)
• polyval_preparekey(9)
• ghash_init(9)
• polyval_init(9)
• polyval_import_blkaligned(9)
• polyval_export_blkaligned(9)
• ghash_update(9)
• polyval_update(9)
• ghash_final(9)
• polyval_final(9)
• ghash(9)

like, the entire polyval/ghash cinematic universe. go read the whole trilogy, iykyk 🌈

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🍓 quick reminder bestie: polyval_preparekey(9) before polyval(9). the keyword is prepared. don't skip steps, we don't skip steps 💖

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mwah — this little page lives in ./include/crypto, dated October 2026, and it's brought to you straight from the Kernel API Manual. periodt. 👑💜