crypto_krb5_calc_PRFplus(9)

💅 crypto_krb5_calc_PRFplus(9) — Kernel API Manual ✨

okay so bestie, welcome to the Kernel API Manual page for crypto_krb5_calc_PRFplus(9) — yes the title and the manual name are both right there, we're being thorough 💖

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🌸 NAME 🌸

crypto_krb5_calc_PRFplus — it calculates PRF+ for you, and the spec it's serving is [RFC4402] 🫶

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🦋 SYNOPSIS 🦋

int crypto_krb5_calc_PRFplus (const struct krb5_enctype *krb5 , const
struct krb5_buffer *K , unsigned int L , const struct krb5_buffer *S ,
struct krb5_buffer *result , gfp_t gfp );

like, that's the whole signature, no cap ✨ just six args and it returns an int 👑

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🎀 ARGUMENTS 🎀

• krb5 — the encryption type you're gonna use, it's giving "which flavor are we doing today" 💅
• K — the protocol key for the pseudo-random function, the main character of the key world 🔑
• L — the length of the output, so you tell it exactly how much slay you want
• S — the input octet string, the lil' input bestie 🍓
• result — the result buffer, and heads up it's sized to krb5->prf_len, don't skimp on it 🙈
• gfp — allocation restrictions, the vibe check for how memory gets grabbed 💀

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⭐ DESCRIPTION ⭐

So what it actually does: it calculates the kerberos pseudo-random function, PRF+(), and it does it by the following method:

PRF+(K, L, S) = truncate(L, T1 || T2 || .. || Tn) Tn = PRF(K, n || S)
[rfc4402 sec 2]

that's it, that's the formula, [rfc4402 sec 2] said it first and we're just honoring the icon 👑 literally just truncating L bytes off the concatenation of T1 through Tn, where each Tn is PRF(K, n || S). obsessed. no notes. periodt 🌈

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🔥 SEE ALSO 🔥

• Kernel file ./crypto/krb5/krb5_kdf.c — yeah that's where the whole thing lives, iykyk 💜
• krb5_derive_Kc(9)
• krb5_derive_Ke(9)
• krb5_derive_Ki(9)

go read those too bestie, they're the friend group 🫶

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💀 real talk though — result literally has to be sized to krb5->prf_len, that's not a suggestion, that's the assignment.

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so yeah! that's the page 💖 it came from ./crypto/krb5, it's dated October 2026, and honestly? the whole thing ate. mwah 😭✨🦋🌸💅