aes_gcm_encrypt(9)

💖 aes_gcm_encrypt(9) — the Kernel API Manual, but make it make sense 💖

okay bestie, so this is a page from the Kernel API Manual and it's all about aes_gcm_encrypt — yes it's giving cryptography, yes it's giving kernel space, and yes we're gonna get through it together. 🫶

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✨ NAME ✨

aes_gcm_encrypt — Encrypt a message with AES-GCM 🔐

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🌸 SYNOPSIS 🌸

void aes_gcm_encrypt (u8 *dst , const u8 *src , size_t data_len , u8
*authtag , const u8 *ad , size_t ad_len , const u8 nonce[static 12] ,
const struct aes_gcm_key *key );

like… look at her. ten arguments. main character energy fr fr. 💅

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🎀 ARGUMENTS 🎀

okay so here's the tea on every single one of these, no skipping, we're doing all of them:

• dst — your destination ciphertext data. It can be in-place or out-of-place, whichever vibe you're on. For other overlaps the behavior is unspecified — so like, don't. 🙈
• src — the source plaintext data. the innocent before-picture.
• data_len — length of plaintext in bytes (and ciphertext excluding the tag): at most 2^36 - 32. that's a real number, bestie, respect it. 🔥
• authtag — the output authentication tag. Its length is the authtag_len that was passed to aes_gcm_preparekey. Usually protocols using AES-GCM put the tag at the end of the ciphertext, in which case this should be set to dst + data_len and dst must have room for the tag. iykyk. ⭐
• ad — the associated data.
• ad_len — length of associated data in bytes: at most 2^61 - 1. big mood, big number. 🌈
• nonce — the 12-byte nonce. and like… All (key, nonce) pairs used MUST be distinct. not optional. not a suggestion. this is the whole entire rule. 💀
• key — the key, already prepared using aes_gcm_preparekey. don't bring an unprepared key to this function, she will not know what to do with it. 😭

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🦋 DESCRIPTION 🦋

So for AES-GMAC (i.e., AES-GCM without any data en/decrypted), use dst=NULL, src=NULL, and data_len=0 to generate the AES-GMAC value. that's the whole move. iconic. ✨

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👑 CONTEXT 👑

Any context. that's it. she's flexible. she's everywhere. she's unbothered. 💜

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🌺 SEE ALSO 🌺

go look at these, they're all her friends and they're all important:

• Kernel file ./include/crypto/aes-gcm.h
• struct aes_gcm_key(9)
• struct aes_gcm_ctx(9)
• aes_gcm_preparekey(9)
• aes_gcm_decrypt(9)
• aes_gcm_init(9)
• aes_gcm_auth_update(9)
• aes_gcm_encrypt_update(9)
• aes_gcm_decrypt_update(9)
• aes_gcm_encrypt_final(9)
• aes_gcm_decrypt_final(9)

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aaaand that's the page!! 🎀 this little number lives over at ./include/crypto and it's dated October 2026 — yes bestie, the future. you read it here. slay. 💅✨🌸