From 0af6f24ab88f1e3afa937d874ea83f12b9da550c Mon Sep 17 00:00:00 2001
From: null <koga.industries@gmail.com>
Date: Wed, 8 Jul 2026 23:21:35 -0500
Subject: [PATCH] =?UTF-8?q?docs(manual):=20batch=203=20review=20=E2=80=94?=
 =?UTF-8?q?=20Argon2id=20memory=20was=2046080=20KiB=20but=20the=20code=20i?=
 =?UTF-8?q?s=2047104?=
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The Argon2id parameter block said:
  - memory: 46 MiB (46080 KiB)
  - iterations: 3
  - parallelism: 1

But the source constant in RecoveryKeyManager.kt is:
  private const val ARGON2_MEMORY_KB = 46 * 1024

46 * 1024 = 47104, not 46080 (a slipped digit). 46080 KiB would be
45 MiB. The iOS-side docstring in CoupleEncryptionManager.swift
already says 46 MiB = 47104 KiB, so this is the Android-side drift.

Replaced the parameter block with the source-of-truth constant names
(ARGON2_MEMORY_KB, ARGON2_ITERATIONS, ARGON2_PARALLELISM) and the
correct KiB value (47104) so the next reader can grep the code.

Other Batch 3 claims verified clean:
- Encryption version table: EncryptionVersion.STRICT=2, acceptInviteCallable
  hardcodes 2, throws if any of wrappedCoupleKey/kdfSalt/kdfParams is null.
- Tink AEAD wire formats: enc:v1:base64, sealed:v1:urlsafe-base64-no-padding,
  keybox:v1:urlsafe-base64-no-padding, pub:v1:urlsafe-base64-no-padding,
  sha256:urlsafe-base64-no-padding (43 chars). All match the source constants.
- AAD: FieldEncryptor uses coupleId; SealedAnswerEncryptor uses
  coupleId|questionId|userId; both match.
- ECIES P-256: UserKeyManager uses
  HybridKeyTemplates.ECIES_P256_HKDF_HMAC_SHA256_AES128_GCM;
  ReleaseKeyEncryptor contextInfo is coupleId|questionId|senderUserId|recipientUserId.
- All 5 firestore.rules regex helpers match the manual's reference table.
- wrapReleaseKeyCallable reads the recipient public key from
  users/{uid}/devices/primary (verified in function source).
- CoupleKeyStore persists Tink keyset handles in EncryptedSharedPreferences
  (Keystore-backed) via SecurePreferencesFactory.
---
 docs/Engineering_Reference_Manual.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/docs/Engineering_Reference_Manual.md b/docs/Engineering_Reference_Manual.md
index cb99c593..66773ddf 100644
--- a/docs/Engineering_Reference_Manual.md
+++ b/docs/Engineering_Reference_Manual.md
@@ -396,9 +396,9 @@ The couple keyset is a Tink AES-256-GCM keyset generated once per couple.
 
 - `RecoveryKeyManager.newCoupleKeyset()` creates the keyset.
 - `RecoveryKeyManager.wrap(keyset, phrase)` derives a 32-byte key with Argon2id:
-  - **memory**: 46 MiB (`46080` KiB)
-  - **iterations**: 3
-  - **parallelism**: 1
+  - **memory**: 46 MiB (`46 * 1024 = 47104` KiB; constant `ARGON2_MEMORY_KB`)
+  - **iterations**: 3 (`ARGON2_ITERATIONS`)
+  - **parallelism**: 1 (`ARGON2_PARALLELISM`)
   - **salt**: 16 random bytes
 - The keyset plaintext is encrypted with AES-256-GCM using the derived key. AAD is the fixed string `"closer_couple_key"` so the blob is portable across invite-code reconciliation.
 - The wrapped result is stored on the couple document as `wrappedCoupleKey`, `kdfSalt`, `kdfParams`.