KCAPI_AKCIPHER_SETPU(3)

💖 KCAPI_AKCIPHER_SETPU(3) 💖

okay bestie, welcome to the Programming Interface section 3 page for kcapi_akcipher_setpubkey — yes the man page header truncates it to KCAPI_AKCIPHER_SETPU(3) like a bad screen name, but we know the truth 🫶

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✨ NAME ✨

kcapi_akcipher_setpubkey — set the public key for the cipher handle 🔑

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🌸 SYNOPSIS 🌸

int kcapi_akcipher_setpubkey(struct kcapi_handle * handle,
                             const uint8_t * key, uint32_t keylen);

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🎀 ARGUMENTS 🎀

• handle — [in] the cipher handle, aka your main character. 💅
• key — [in] the key buffer, and it has to be in DER format, no substitutes. 📜
• keylen — [in] how long that key buffer is. 📏

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🦋 DESCRIPTION 🦋

So like, this function is the moment where you hand over the key for all the cipher operations coming after it. No key, no vibes, no crypto. 🔥

The key has to be in DER format, and specifically it looks like this, okay?

SEQUENCE { n INTEGER ({ rsa_get_n }), e INTEGER ({ rsa_get_e }) }

That's the shape. n, e, SEQUENCE, all of it. Not me being extra, that's just literally the requirement. 💀

Once you've passed the key in, you're free to securely destroy it — because at that point the kernel is the one maintaining it. She's got it from here, bestie, you can let go. 🙈

And on the return tip: when it works, the value returned is the maximum size for the asymmetric operation (like, say, the modulus size). When it doesn't work? You get a negative errno-style error code. So if you're staring at a negative number, that's not a size, that's a whole situation. 😭

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👑 AUTHOR 👑

Stephan Mueller <smueller@chronox.de>

• Author. (iconic of him, fr fr ⭐)

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💜 COPYRIGHT 💜

This page lives under the libkcapi banner — no extra copyright lines were written down here on this page, so that's the whole story. 🧚

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okay that's the whole page, no cap. sending you off with all the love: libkcapi Manual 1.5.0, July 2025 — go set that public key and slay, bestie 💅✨🎀🦋🌸