aes_preparekey(9)

✨ aes_preparekey(9) ✨

the kernel api manual page you didn't know you needed 💖

okay so bestie, this is aes_preparekey, a function from the Kernel API Manual, and honestly? she's a little workhorse and she deserves her flowers 🌸

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🌈 NAME 🌈

aes_preparekey — prepare an AES key for encryption and decryption, both directions, no cap 💅

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🎀 SYNOPSIS 🎀

int aes_preparekey (struct aes_key *key , const u8 *in_key , size_t
key_len );

that's the whole vibe. three args, one int back. iconic signature fr 🫶

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🦋 ARGUMENTS 🦋

• key — (output) the key structure you're initializing. she's the destination, the main character, the one getting filled in ✨
• in_key — the raw AES key. the actual secret juice 🔥
• key_len — length of the raw key, in bytes. should be either AES_KEYSIZE_128, AES_KEYSIZE_192, or AES_KEYSIZE_256. like, pick one of those three, that's the whole menu 🍓

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💜 DESCRIPTION 💜

so what she does is: this prepares an AES key for both the encryption and decryption directions of the block cipher. both! multitalented! 🌟

typically that involves expanding the raw key into both the standard round keys and the Equivalent Inverse Cipher round keys — but ngl, some architecture-specific implementations don't do the full expansion here. so like, don't assume, iykyk 🧚

important!! bestie, the caller is responsible for zeroizing both the struct aes_key and the raw key once they're no longer needed. that's on you, not on her. please don't leave secrets lying around 🙈

and if you don't need decryption support at all? then use aes_prepareenckey instead — why do the full expansion when you only need one direction, right? 💅

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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 you're a caller who always passes a valid key length, you don't even need to check for errors. slay, low-maintenance queen 👑

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🌸 CONTEXT 🌸

Any context. literally wherever, whenever, she's ready 🦋

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👑 SEE ALSO 👑

• Kernel file ./include/crypto/aes.h
• struct aes_enckey(9)
• struct aes_key(9)
• aes_expandkey(9)
• aes_prepareenckey(9)
• aes_encrypt(9)
• aes_decrypt(9)

the whole friend group, go say hi 🫶✨

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okay that's the page!! this little gem lives in ./include/crypto and the version/date on the tin is October 2026 — mwah, go encrypt something responsibly, ily, bye 💖🎀💅