210232d156
Punch items from doc audit: - docs/ARCHITECTURE.md: encrypted file format diagram said version byte 0x01; actual VERSION_BYTE is 0x02 (crypto.rs:59) and 0x01 is rejected with UnsupportedFormatVersion. - docs/ARCHITECTURE.md: DCT embedding diagram said "Repeat secret 20+ times" and "positions 4-15"; actual is MIN_COPIES (5) to 50 copies chosen by capacity, embedded in zig-zag positions 6-17 (imgsecret.rs:78, 99-104, 530-537). - FORMATS.md: AttachmentId table said 16 hex chars / 8 bytes; actual is 32 hex chars / first 16 bytes of SHA-256 (ids.rs:59-69). - FORMATS.md: ManifestEntry schema missing r#type field; updated to list all ten fields in declared order with serde decorations noted (manifest.rs:21-38). Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
277 lines
18 KiB
Markdown
277 lines
18 KiB
Markdown
# Relicario — Architecture
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## System Overview
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```
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┌──────────────────────────────────────────────────────────────────┐
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│ CLIENT DEVICE (trusted) │
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│ │
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│ ┌─────────────┐ ┌──────────────┐ ┌──────────────────────┐ │
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│ │ Reference │ │ Passphrase │ │ relicario-cli │ │
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│ │ JPEG │ │ (typed) │ │ or browser ext │ │
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│ │ (on disk) │ │ │ │ │ │
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│ └──────┬───────┘ └──────┬───────┘ └──────────┬───────────┘ │
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│ │ │ │ │
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│ ▼ │ │ │
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│ ┌──────────────┐ │ │ │
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│ │ imgsecret │ │ │ │
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│ │ ::extract() │ │ │ │
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│ └──────┬───────┘ │ │ │
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│ │ │ │ │
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│ ▼ ▼ │ │
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│ ┌──────────────────────────────┐ │ │
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│ │ Argon2id KDF │ │ │
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│ │ password = passphrase ‖ │ │ │
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│ │ image_secret │ │ │
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│ │ salt = vault_salt │ │ │
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│ │ → master_key (32 bytes) │ │ │
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│ └──────────────┬───────────────┘ │ │
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│ │ │ │
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│ ▼ │ │
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│ ┌──────────────────────────────┐ │ │
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│ │ XChaCha20-Poly1305 │◄──────────────────┘ │
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│ │ encrypt / decrypt │ │
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│ │ (192-bit nonce, 256-bit │ │
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│ │ key, 128-bit auth tag) │ │
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│ └──────────────┬───────────────┘ │
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│ │ │
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└─────────────────┼──────────────────────────────────────────────────┘
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│
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│ git push / pull (HTTPS or SSH)
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▼
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┌──────────────────────────────────────────────────────────────────┐
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│ GIT SERVER (untrusted) │
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│ │
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│ relicario-vault.git/ │
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│ ├── manifest.enc ← opaque ciphertext │
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│ ├── settings.enc ← opaque ciphertext │
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│ ├── items/ │
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│ │ ├── a1b2c3d4e5f6a7b8.enc ← opaque ciphertext │
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│ │ └── … │
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│ ├── attachments/ │
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│ │ └── <item-id>/<aid>.enc ← opaque ciphertext │
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│ └── .relicario/ │
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│ ├── salt ← 32 bytes (not secret) │
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│ ├── params.json ← KDF params (not secret) │
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│ ├── devices.json ← device public keys (not secret) │
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│ └── revoked.json ← revoked device records (not secret) │
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│ │
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│ The server sees NOTHING useful. No keys, no plaintext, │
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│ no metadata about what's inside. │
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└──────────────────────────────────────────────────────────────────┘
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```
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## Vault Creation Flow
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```
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User provides: System generates:
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├── carrier JPEG (any photo) ├── image_secret (256-bit random)
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└── passphrase (memorized) └── vault_salt (256-bit random)
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┌──────────────────┐
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carrier JPEG ──────►│ imgsecret │──────► reference.jpg
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image_secret ──────►│ ::embed() │ (looks like a normal photo,
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│ DCT stego │ carries hidden secret)
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└──────────────────┘
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┌──────────────────┐
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passphrase ────────►│ │
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│ Argon2id │──────► master_key (32 bytes)
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image_secret ──────►│ (64 MiB, 3 it) │ (held in memory only)
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vault_salt ────────►│ │
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└──────────────────┘
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┌──────────────────┐
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master_key ────────►│ XChaCha20- │──────► manifest.enc
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empty manifest ────►│ Poly1305 │ settings.enc
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default settings ──►│ encrypt (×2) │ (parallel artifacts;
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└──────────────────┘ independent nonces)
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┌──────────────────┐
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│ git init │──────► vault repo
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│ git commit │ (ready to push)
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└──────────────────┘
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```
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Item creation, the typed-item envelope (`Item` + per-type `ItemCore`),
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attachment encryption, and field-history tracking are not shown above —
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they are described in [`crates/relicario-core/ARCHITECTURE.md`](../crates/relicario-core/ARCHITECTURE.md).
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The flow above covers only the crypto-pipeline shape that vault init
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establishes; the per-item lifecycle reuses the same `master_key` +
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XChaCha20-Poly1305 primitives against `items/<id>.enc` and
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`attachments/<item-id>/<aid>.enc`.
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## Unlock Flow (every vault operation)
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```
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┌──────────────────┐
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reference.jpg ─────►│ imgsecret │──────► image_secret
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│ ::extract() │ (256 bits)
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└──────────────────┘
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┌──────────────────┐
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passphrase ────────►│ │
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image_secret ──────►│ Argon2id │──────► master_key
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vault_salt ────────►│ │
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└──────────────────┘
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┌──────────────────┐
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master_key ────────►│ XChaCha20 │──────► plaintext entries
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*.enc files ───────►│ ::decrypt() │ (in memory only)
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└──────────────────┘
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```
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## imgsecret DCT Embedding
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```
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Input JPEG
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│
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▼
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┌──────────────────┐
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│ Decode to RGB │
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│ Extract Y │
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│ (luminance) │
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└────────┬─────────┘
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│
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▼
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┌──────────────────────────────┐
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│ Full Image │
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│ ┌────────────────────────┐ │
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│ │ 15% ┌────────────┐ │ │
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│ │margin│ │15% │ │
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│ │ │ Central │mar-│ │
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│ │ │ 70% │gin │ │
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│ │ │ EMBEDDING │ │ │
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│ │ │ REGION │ │ │
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│ │ └────────────┘ │ │
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│ │ 15% margin │ │
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│ └────────────────────────┘ │
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└──────────────────────────────┘
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│
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▼
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┌──────────────────┐
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│ Divide into │
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│ 8×8 blocks │
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│ Apply 2D DCT │
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└────────┬─────────┘
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│
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▼
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┌──────────────────┐
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│ For each │
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│ selected block: │
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│ │
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│ QIM embed bits │
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│ in zig-zag │
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│ positions 6-17 │
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│ (mid-frequency) │
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│ │
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│ Repeat secret │
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│ MIN_COPIES (5) │
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│ to 50 times, │
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│ by capacity │
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└────────┬─────────┘
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│
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▼
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┌──────────────────┐
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│ Inverse DCT │
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│ Reconstruct RGB │
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│ Save JPEG (Q92) │
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└──────────────────┘
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│
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▼
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Output: reference.jpg
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(visually identical,
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carries 256-bit secret)
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```
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The redundancy count is chosen at embed time based on available DCT capacity: `num_copies = (total_blocks / BLOCKS_PER_COPY).min(50)`, with `BLOCKS_PER_COPY = 22` and a floor of `MIN_COPIES = 5` (`crates/relicario-core/src/imgsecret.rs:78,530-537`). Images that cannot fit at least 5 copies are rejected before embed. Majority voting across these copies at extract time requires ≥ 60 % confidence per bit.
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## Extraction (with crop recovery)
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```
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Input JPEG (possibly re-encoded or cropped)
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│
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▼
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┌─────────────────────────┐
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│ Try canonical alignment │──── Success ──► image_secret
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│ (offset 0,0) │
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└─────────┬───────────────┘
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│ Fail
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▼
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┌─────────────────────────┐
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│ Search crop offsets │
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│ dx, dy: -15% to +15% │
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│ step: 8 pixels │
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│ (~16,800 candidates) │──── Success ──► image_secret
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│ │
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│ For each: extract bits, │
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│ majority vote, check │
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│ confidence ≥ 60% │
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└─────────┬───────────────┘
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│ All fail
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▼
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ExtractionFailed error
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```
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## Encrypted File Format
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```
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┌─────────┬────────────────────────┬──────────────────┬──────────────────┐
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│ version │ nonce │ ciphertext │ auth tag │
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│ 1 byte │ 24 bytes │ N bytes │ 16 bytes │
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│ 0x02 │ random per write │ XChaCha20 stream │ Poly1305 MAC │
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└─────────┴────────────────────────┴──────────────────┴──────────────────┘
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```
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`VERSION_BYTE = 0x02` (`crates/relicario-core/src/crypto.rs:59`). Blobs starting with any other byte are rejected with `UnsupportedFormatVersion { found, expected: 0x02 }`. The legacy `0x01` format from the pre-typed-items era is no longer supported.
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## Crate Architecture
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```
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┌────────────────────────────────────────────────────────────┐
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│ relicario-cli │
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│ Filesystem, git (shelling out), terminal I/O, clipboard │
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│ │
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│ Depends on: relicario-core, clap, anyhow, rpassword, arboard │
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└──────────────────────┬─────────────────────────────────────┘
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│ uses
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▼
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┌────────────────────────────────────────────────────────────┐
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│ relicario-core │
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│ Platform-agnostic: bytes in, bytes out │
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│ No filesystem, no network, no git │
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│ │
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│ ┌──────────┐ ┌──────────┐ ┌─────────┐ ┌────────────┐ │
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│ │ crypto │ │ imgsecret│ │ item + │ │ vault │ │
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│ │ │ │ │ │ types │ │ │ │
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│ │ KDF │ │ DCT │ │ Item │ │ encrypt_ │ │
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│ │ encrypt │ │ embed │ │ Manifest│ │ item() │ │
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│ │ decrypt │ │ extract │ │ Settings│ │ decrypt_ │ │
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│ │ │ │ QIM │ │ Backup │ │ manifest() │ │
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│ │ │ │ │ │ Device │ │ ... │ │
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│ └──────────┘ └──────────┘ └─────────┘ └────────────┘ │
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│ │
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│ Consumed by: relicario-cli, relicario-wasm (extension), │
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│ relicario-server (pre-receive hook). │
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│ Future: JNI/Swift wrappers for Android/iOS. │
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└────────────────────────────────────────────────────────────┘
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```
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## Entropy at Each Attack Scenario
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```
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Server breach only: ████████████████████████████ 256+ bits (infeasible)
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passphrase + image_secret
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Server + stolen image: ████░░░░░░░░░░░░░░░░░░░░░░ ~51 bits (4 diceware words)
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passphrase through Argon2id ~7 million years
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Shoulder-surfed passphrase: ████████████████████████████ 256 bits (infeasible)
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image_secret
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Stolen device: ████░░░░░░░░░░░░░░░░░░░░░░ ~51 bits (4 diceware words)
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passphrase through Argon2id ~7 million years
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Both factors compromised: game over (same as every password manager)
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```
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