aes_ccm_decrypt_update(9)

✨ aes_ccm_decrypt_update — incrementally decrypt data with AES-CCM ✨

okay so bestie, welcome to the aes_ccm_decrypt_update(9) page 🫶 it lives in the Kernel API Manual and it's literally the "keep decrypting in chunks" girlie of the AES-CCM family. let's get into it 💅

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🌸 SYNOPSIS 🌸

void aes_ccm_decrypt_update (struct aes_ccm_ctx *ctx , u8 *dst , const
u8 *src , size_t len );

that's the whole vibe. one function, four args, and it returns void (so no return value to check, she just does it 💖).

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🎀 ARGUMENTS 🎀

• ctx — an AES-CCM context. like, the main character struct holding all your state 🧚
• dst — the destination buffer, aka where the plaintext lands 💫. it can be in-place or out-of-place, no cap. but for other overlaps the behavior is unspecified 😭 so don't try to be cute with weird overlapping buffers, okay? that's giving undefined and we don't stan.
• src — the source ciphertext data 🔒 — and just to be super clear, this does not include the auth tag. the tag is a separate thing, bestie.
• len — number of bytes to decrypt 📏 literally just how much you're decrypting this round.

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🦋 DESCRIPTION 🦋

so here's the tea ☕: you can call this only after all associated data has been processed. like, that's a prerequisite, not a suggestion 🙈.

also — and this is highkey important — the total length of the decrypted data (over all calls to this function) MUST match the data_len that was passed to aes_ccm_init. so if you init'd with a data_len, every single len you feed this function across all your calls has to add up to exactly that. no more, no less, periodt 💯.

⚠️ IMPORTANT: callers MUST NOT assume that any decrypted or associated data is authentic until the authentication tag has been verified 🔥 like, do NOT trust that data yet, bestie, it has not earned your trust. verify the tag first, then you can relax 💅

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👑 CONTEXT 👑

any context 🎉 that's it, she's flexible, she's low-maintenance, she slays in any context.

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🌈 SEE ALSO 🌈

• kernel file ./include/crypto/aes-ccm.h
• struct aes_ccm_key(9)
• struct aes_ccm_ctx(9)
• aes_ccm_preparekey(9)
• aes_ccm_encrypt(9)
• aes_ccm_decrypt(9)
• aes_ccm_init(9)
• aes_ccm_auth_update(9)
• aes_ccm_encrypt_update(9)
• aes_ccm_encrypt_final(9)
• aes_ccm_decrypt_final(9)

the whole friend group fr fr 💜

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and that's the page!! 🍓 source/location is ./include/crypto and this iconic little doc is dated October 2026 — go forth and decrypt incrementally, bestie, and remember: verify that tag before you trust anyone 😤💖