aes_prepareenckey(9)

💖 aes_prepareenckey(9) — Kernel API Manual 💖

okay so bestie, welcome to the glow-up era of aes_prepareenckey 💅 this one lives in the Kernel API Manual and it's genuinely such a slay little function — it sets you up an AES key for encryption only, no decryption, no drama.

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✨ NAME ✨

aes_prepareenckey — prepare an AES key for encryption-only 🎀

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🌸 SYNOPSIS 🌸

int aes_prepareenckey (struct aes_enckey *key , const u8 *in_key ,
size_t key_len );

like, look at her. three args. icon behavior.

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🦋 ARGUMENTS 🦋

• key — (output) the key structure you're gonna initialize 💖 this is where the magic lands.
• in_key — the raw AES key, straight up, no filter.
• key_len — length of the raw key in bytes. should be either AES_KEYSIZE_128, AES_KEYSIZE_192, or AES_KEYSIZE_256. those three, bestie. no other vibes accepted.

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👑 DESCRIPTION 👑

so what does she actually do? this prepares an AES key for only the encryption direction of the block cipher. that's the whole assignment, and she eats every time 🔥

typically that means expanding the raw key into only the standard round keys — which means you end up with a struct about half the size of struct aes_key. smaller struct, same main character energy.

⚠️ okay this part is important, don't scroll past it: the caller is responsible for zeroizing both the struct aes_enckey and the raw key once they're no longer needed. that's on you, not her. take care of your secrets fr fr 🙈

and here's the lil plot twist that's actually lowkey iconic — even though the resulting prepared key only supports AES encryption, it can still be used for decrypting in a mode of operation that uses AES in only the encryption (forward) direction. counter mode is the example. so yeah, she's encryption-only but she's still showing up for the decrypt shift when the mode says so 😭💀

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🌈 RETURN 🌈

• 0 on success 🎉
• -EINVAL if the given key length is invalid 🚫

and that's literally it — no other errors are possible, so if your callers always pass a valid key length, they don't need to check for errors at all. no error-checking anxiety required. she's low-maintenance. 🫶

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⭐ CONTEXT ⭐

Any context. she does not gatekeep, she's welcome everywhere 💜

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🎀 SEE ALSO 🎀

Kernel file ./include/crypto/aes.h struct aes_enckey(9), struct aes_key(9), aes_expandkey(9), aes_preparekey(9), aes_encrypt(9), aes_decrypt(9) — go read the whole friend group, they're all linked 💖

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and that's the page!! brought to you by ./include/crypto, the October 2026 edition of aes_prepareenckey(9) — mwah, go zeroize your keys, ily, bye 🧚✨