aes_gcm_decrypt_update(9)

💅 aes_gcm_decrypt_update(9) 💅

okay so welcome to the aes_gcm_decrypt_update(9) page in the Kernel API Manual — this one is all about incrementally decrypting data with AES-GCM, and yes bestie, the security caveat is very much the main character here. 🫶

---

✨ NAME ✨

aes_gcm_decrypt_update — Incrementally decrypt data with AES-GCM 💖

---

🎀 SYNOPSIS 🎀

void aes_gcm_decrypt_update (struct aes_gcm_ctx *ctx , u8 *dst , const
       u8 *src , size_t len );

---

🫶 ARGUMENTS 🫶

• ctx — An AES-GCM context. literally the context bestie, it's giving "you need this" energy.
• dst — The destination buffer. Can be in-place or out-of-place. For other overlaps the behavior is unspecified — so like, don't get creative with overlapping buffers unless it's one of those two, mwah. 💅
• src — The source ciphertext data (not including auth tag). no tag in here, keep it out. 🙈
• len — Number of bytes to decrypt. The caller must ensure that the total number of bytes decrypted doesn't exceed GCM's limit of 2^36 - 32. yes, that exact limit, no cap. 😤

---

🌸 DESCRIPTION 🌸

This can be called only after all associated data has been processed. like, that's the prerequisite, bestie, don't skip it. ✨

IMPORTANT: Callers MUST NOT assume that any decrypted or associated data is authentic until the authentication tag has been verified. 🚨

that is the whole vibe check, fr fr: no data is "authentic" until that authentication tag is verified. do not be trusting plaintext early, it's not the moment. 💀

---

🦋 CONTEXT 🦋

Any context. any context, bestie — iconic flexibility. 🌈

---

👑 SEE ALSO 👑

• Kernel file ./include/crypto/aes-gcm.h
• struct aes_gcm_key(9)
• struct aes_gcm_ctx(9)
• aes_gcm_preparekey(9)
• aes_gcm_encrypt(9)
• aes_gcm_decrypt(9)
• aes_gcm_init(9)
• aes_gcm_auth_update(9)
• aes_gcm_encrypt_update(9)
• aes_gcm_encrypt_final(9)
• aes_gcm_decrypt_final(9)

---

that's the page, bestie 🫶 — source/version is ./include/crypto, dated October 2026, and it's the aes_gcm_decrypt_update(9) page. periodt. 💅