chacha_block_generic(9)

💅 chacha_block_generic(9)

okay so bestie, welcome to the Kernel API Manual — yes we're in the kernel now, bring your sparkliest brain cell. today's main character is chacha_block_generic, and she is literally the ChaCha core itself. no cap. 🌀✨

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✨ NAME ✨

chacha_block_generic — generate one keystream block and increment block counter 🎀

like, she makes you one keystream block, and as a little bonus she bumps the block counter for you on the way out. multitasking queen. 👑

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🌸 SYNOPSIS 🌸

void chacha_block_generic (struct chacha_state *state , u8
out[CHACHA_BLOCK_SIZE] , int nrounds );

copy that exactly, don't @ me. 🫶

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🦋 ARGUMENTS 🦋

• state — the input state matrix. this is where the vibes (and the counter) live going in.
• out — the output keystream block. it's u8 out[CHACHA_BLOCK_SIZE], so she's got exactly the room she needs. 💖
• nrounds — number of rounds, and it's either 20 or 12. 20 is the recommended one, so like… pick 20 unless you have a reason. iykyk. 🔥

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💀 DESCRIPTION 💀

This is the ChaCha core, fr fr — a function from 64-byte strings to 64-byte strings. 64 bytes in, 64 bytes out, that's the whole personality. 🌈

important detail: the caller has already converted the endianness of the input. so don't come for her about endianness, that's not her job, that was done before she showed up. 🙈

she also handles incrementing the block counter in the input matrix — so yes, she mutates the input state matrix's block counter as part of the deal. not me getting a side effect in a crypto function, but honestly? iconic. ✨

heads up bestie: state is a pointer and the block counter inside it gets incremented — that's the documented behaviour, so plan accordingly. 💅

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🔍 SEE ALSO 🔍

• the kernel file ./lib/crypto/chacha-block-generic.c — go read the source, she's right there 👀
• hchacha_block_generic(9) — her cousin, also slaying 💜

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okay that's the whole page, you ate that. she's from ./lib/crypto, this is the October 2026 era, and it's all under the Kernel API Manual banner — periodt. 💅🎀🦋✨