STRUCT DCP_BLOB_FMT(9)

💖 struct dcp_blob_fmt(9) — like, the DCP BLOB format bestie 💖

okay so this is a page from the Kernel API Manual and it's all about struct dcp_blob_fmt, which is literally the DCP BLOB format. no cap. let's get into it 🫶

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✨ SYNOPSIS ✨

here's the whole struct, bestie — every single field, exactly as it is, no notes:

struct dcp_blob_fmt {
    __u8 fmt_version;
    __u8 blob_key[AES_KEYSIZE_128];
    __u8 nonce[AES_KEYSIZE_128];
    __le32 payload_len;
    __u8 payload[];
 };

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🎀 Members 🎀

• fmt_version — the format version, and rn it's 1. that's the vibe. one. 💅
• blob_key — a random AES 128 key that's used to encrypt the payload. plot twist tho: blob_key itself gets encrypted with the OTP or UNIQUE device key in AES-128-ECB mode by DCP. so it's keys all the way down, iykyk 🔥
• nonce — a random nonce, used for the payload encryption. iconic behavior honestly.
• payload_len — the length of the plain text payload. just the length, she's not the payload herself, she just knows her. 💀
• payload — the payload itself!! encrypted using AES-128-GCM and blob_key, and a GCM auth tag of size DCP_BLOB_AUTHLEN is attached at the end of it. so the tag is like, right there at the tail, holding it together 🌸

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🦋 Description 🦋

the total size of a DCP BLOB is literally this:

sizeof(struct dcp_blob_fmt) + payload_len + DCP_BLOB_AUTHLEN

that's it, that's the math, and it ate 💖

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🌈 SEE ALSO 🌈

• the Kernel file ./security/keys/trusted-keys/trusted_dcp.c
• dcp blob format(9) — yes that's the ref, go read it bestie 👑

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ngl the whole thing is giving "crypto struct that knows exactly what she is" and honestly? obsessed. 🍓

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okay bye bestie, this page lives in ./security/keys/trusted-keys and it's dated October 2026 — mwah, slay, periodt 🧚‍♀️💜