nh(9)

💖 nh(9) — like, the NH hash function for Adiantum, bestie 💖

okay so this is a page from the Kernel API Manual (that's the manual name, iykyk) and it's all about nh, the NH hash function that Adiantum uses. it's giving crypto-core, it's giving "i read the Adiantum paper," and honestly? we're obsessed. let's get into it 🫶

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✨ SYNOPSIS ✨

void nh (const u32 *key , const u8 *message , size_t message_len ,
__le64 hash[NH_NUM_PASSES] );

like, that's the whole vibe right there 👑

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🎀 ARGUMENTS 🎀

• key — the key, babes. message_len + 48 bytes of it get used. and if message_len is at its maximum length of NH_MESSAGE_BYTES, then that's exactly NH_KEY_BYTES. math is mathing 💅
• message — the message. yeah, that's it. that's the message 📨
• message_len — the message length in bytes. lowkey strict about this one: it must be a multiple of 16 (NH_MESSAGE_UNIT) and at most 1024 (NH_MESSAGE_BYTES). no cap, it will not accept your weird lengths 🙈
• hash — (output) the resulting hash value. this is where the slay gets written ✨

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⚠️ NOTE ⚠️

okay so this is the part where you gotta pay attention, bestie, because it's a whole thing 👀

the pseudocode for NH in the Adiantum paper iterates over 1024-byte segments of the message, computes a 32-byte hash for each one, and returns all the hashes concatenated together.

in contrast, this function? it just hashes one segment and returns one hash. that's it. one and done 🎯

so it's the caller's responsibility to call this function for each 1024-byte segment and collect all the hashes. yes, you. you're the main character here, you gotta do the collecting 🧺

fr fr, don't forget this part or your hash will be short and sad 😭

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🌈 CONTEXT 🌈

Any context. literally any. go off, king 👑

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🦋 SEE ALSO 🦋

• Kernel file ./include/crypto/nh.h — go read it, it's iconic 💜

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and that's the page, bestie!! 🎀✨

signed off with love from ./include/crypto — version/date vibes: October 2026 🌸 and remember: nh(9) forever and always 💖