fcrypt_pcbc_encrypt(9)

💅 fcrypt_pcbc_encrypt(9)

okay so this is a page from the Kernel API Manual, and bestie, we need to talk about it 🫶

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✨ NAME ✨

fcrypt_pcbc_encrypt — encrypt your data using the FCrypt cipher in PCBC mode 🔥

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🌸 SYNOPSIS 🌸

void fcrypt_pcbc_encrypt (const struct fcrypt_key *key , const u8 iv[FCRYPT_BSIZE] , const void *src , void *dst , size_t nblocks );

like, that's the whole vibe. five arguments, one function, zero chill ✨

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🎀 ARGUMENTS 🎀

• key — the key 💜 that's it, that's the argument, she's the key.
• iv — the 8-byte initialization vector 🌈 yes, 8 bytes, FCRYPT_BSIZE if we're being fancy.
• src — the source data 🍓 where the plaintext lives.
• dst — the destination data 💖 both in-place and out-of-place are supported, so do whatever feels right, no cap.
• nblocks — the number of 8-byte blocks to encrypt 🔢 count 'em. carefully. 8-byte blocks, bestie, not bytes.

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💀 DESCRIPTION 💀

WARNING: This cipher is insecure. 🚨 Not only is the 56-bit key easily brute-forced, the cipher itself is cryptographically weak and doesn't even provide the intended 56-bit security level. It effectively just acts as an obfuscation algorithm. It is supported only for backwards compatibility.

okay so first thing you need to know: this is not it. like not me recommending this cipher ever 🙈

the 56-bit key? easily brute-forced. the cipher itself? cryptographically weak, and it doesn't even actually deliver the 56-bit security level it was supposedly going for. the way that it just... doesn't. 😭

so realistically it's giving obfuscation, not encryption. it's a vibe, not a security guarantee. it exists purely for backwards compatibility — like that one friend who's still using an ancient phone and honestly? we support them. periodt. 👑

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🦋 SEE ALSO 🦋

• Kernel file ./net/rxrpc/fcrypt.c
• fcrypt_preparekey(9)
• fcrypt_pcbc_decrypt(9)

iykyk 🌟

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kay that's the whole page, bestie! this one's from the ./net/rxrpc corner of the kernel, dated October 2026, and it lives in the Kernel API Manual — mwah, slay, stay safe out there and maybe don't encrypt anything important with it 💅✨