Security Architecture

LSPV Security Architecture — 8 Layers of Protection

Zero cloud. Zero telemetry. Zero trust.
Every password you store passes through 8 independent security layers before touching disk.

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Implementation Status by Level (v0.3.1)

Level 1 — Cryptographic Core

Property	Status	Details
Argon2id KDF (m=256MB, t=4, p=4)	✅	core-vault/src/crypto/ — RFC 9106 compliant
XChaCha20-Poly1305 AEAD	✅	Envelope encryption + per-record with unique nonce
Constant-time MAC comparison	✅	sodium_memcmp() for all hash/MAC checks
Memory safety (mlock + zeroize)	✅	sodium_mlock() + sodium_memzero() on lock
OS Keychain (DPAPI / libsecret)	✅	keyring = "2" crate
Auto-lock idle timer	✅	Configurable timeout + lock-on-minimize
Keychain status UI	✅	Settings → Security → OS Keychain: status + Remove button

Level 1 — Storage Hardening

Property	Status	Details
SQLCipher AES-256 per page	✅	rusqlite + sqlcipher feature
Atomic write (tmp → fsync → rename)	✅	Never writes directly to vault.db
Symlink rejection (O_NOFOLLOW)	✅	lstat() check before open
Honeypot ransomware detection	✅	Hash verified on every unlock
Process hardening (PR_SET_DUMPABLE=0)	✅	harden_process() — first call in run() on Linux

Level 2 — Browser Extension

Property	Status	Details
MV3 manifest, zero network requests	✅	connect-src 'none' in CSP
Ed25519 mutual IPC authentication	✅	Desktop signs every response; extension verifies
eTLD+1 domain matching	✅	tldts library — subdomain spoofing prevented
CSP + SRI integrity check in CI	✅	extension/scripts/sri-check.js in security.yml

Level 3 — Encrypted Backups

Property	Status	Details
BIP-39 24-word mnemonic (256 bit)	✅	bip39 = "2" crate
Backup export UI (4×6 grid + verify)	✅	Settings → Backup tab
Argon2id backup KDF (4 GB, 10 iter)	✅	core-vault/src/backup/
.vbk + BLAKE3 integrity check	✅	Checksum verified on restore
Auto-rotation — 7 most recent copies	✅	auto_save_backup() on each manual export

Threat Model (STRIDE/PASTA)

Attack	Mitigation
DLL/SO hijacking	libsodium statically linked — zero external DLL surface
GPU VRAM residue (LeftoverLocals)	sodium_mlock + PR_SET_DUMPABLE=0
Supply chain (XZ-utils style)	cargo-audit in CI; minimal dependency count
Windows Cloud Clipboard	CF_EXCLUDEFROMCLOUDCLIPBOARD

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The 8-Layer Model

╔══════════════════════════════════════════════════════════════════════╗
║                     YOU & YOUR MASTER PASSWORD                       ║
╚══════════════════════╦═══════════════════════════════════════════════╝
                       │
         ┌─────────────▼──────────────────────────────────────────┐
         │  LAYER 1 — KEY DERIVATION (Argon2id)                   │
         │                                                         │
         │  Master Password + 32-byte random Salt                  │
         │       ↓  Argon2id  (256 MB RAM · 4 iterations)          │
         │  ┌──────────────┬──────────────┬──────────────┐         │
         │  │  db_key      │  enc_key     │ search_key   │         │
         │  │  (32 bytes)  │  (32 bytes)  │  (32 bytes)  │         │
         │  │  SQLCipher   │  Vault Key   │  HMAC index  │         │
         │  └──────────────┴──────────────┴──────────────┘         │
         │  Brute-force cost: ~2-4 seconds per attempt on RTX 4090  │
         └─────────────┬───────────────────────────────────────────┘
                       │
         ┌─────────────▼───────────────────────────────────────────┐
         │  LAYER 2 — ENVELOPE ENCRYPTION                           │
         │                                                          │
         │  Random Vault Key (32 bytes, generated ONCE at create)   │
         │       ↓  XChaCha20-Poly1305 (libsodium secretbox)        │
         │  encrypted_vault_key  stored in vault table              │
         │                                                          │
         │  Password change = re-encrypt Vault Key only             │
         │  Records untouched — Vault Key stays the same            │
         └─────────────┬───────────────────────────────────────────┘
                       │
         ┌─────────────▼───────────────────────────────────────────┐
         │  LAYER 3 — RECORD ENCRYPTION (XChaCha20-Poly1305)        │
         │                                                          │
         │  Each record encrypted INDEPENDENTLY with:               │
         │  • Unique 192-bit nonce (new on every save)              │
         │  • Associated data: item_id + field_name (domain sep.)   │
         │  • Authenticated: MAC covers ciphertext + AD             │
         │                                                          │
         │  Flip 1 bit → authentication fails → record rejected     │
         │  No two records share a nonce — ever                     │
         └─────────────┬───────────────────────────────────────────┘
                       │
         ┌─────────────▼───────────────────────────────────────────┐
         │  LAYER 4 — DATABASE ENCRYPTION (SQLCipher)               │
         │                                                          │
         │  The .db file is AES-256-CBC encrypted page-by-page      │
         │  Key = db_key (from Argon2id, never stored on disk)      │
         │  Opening the file without db_key → reads as random noise │
         │                                                          │
         │  Even if vault.db is stolen → unreadable binary blob     │
         └─────────────┬───────────────────────────────────────────┘
                       │
         ┌─────────────▼───────────────────────────────────────────┐
         │  LAYER 5 — OS KEYCHAIN (Windows Credential Manager)      │
         │                                                          │
         │  After unlock: Vault Key cached in OS Keychain           │
         │  Enables quick re-open without re-entering password      │
         │  On lock(): Keychain entry DELETED, not just cleared      │
         │  Keychain protected by Windows DPAPI (hardware-backed)   │
         │                                                          │
         │  No Keychain access = no quick unlock = full Argon2id    │
         └─────────────┬───────────────────────────────────────────┘
                       │
         ┌─────────────▼───────────────────────────────────────────┐
         │  LAYER 6 — MEMORY PROTECTION                             │
         │                                                          │
         │  mlock()   — keys pinned, OS cannot swap to disk         │
         │  zeroize   — keys overwritten with 0x00 on lock/drop     │
         │  Rust ownership — no dangling key references possible    │
         │  No core dumps, no ptrace attach (PR_SET_DUMPABLE=0)     │
         │                                                          │
         │  Auto-lock: 5 min idle · on minimize · on sleep          │
         └─────────────┬───────────────────────────────────────────┘
                       │
         ┌─────────────▼───────────────────────────────────────────┐
         │  LAYER 7 — CLIPBOARD PROTECTION                          │
         │                                                          │
         │  Copied password → auto-cleared after 30 seconds         │
         │  CF_EXCLUDEFROMCLOUDCLIPBOARD — not synced to MS cloud   │
         │  Lock event → clipboard cleared immediately              │
         │  Passwords never logged, never in URL params             │
         └─────────────┬───────────────────────────────────────────┘
                       │
         ┌─────────────▼───────────────────────────────────────────┐
         │  LAYER 8 — OFFLINE BACKUP (BIP-39 + age encryption)      │
         │                                                          │
         │  24-word mnemonic (256-bit BIP-39 entropy)               │
         │  Shown ONCE at vault creation — never stored on disk      │
         │  Backup KDF: Argon2id 4 GB RAM · 10 iterations           │
         │  Format: age-encrypted .vbk + BLAKE3 integrity check     │
         │                                                          │
         │  Even with file stolen: 4 GB/attempt ≈ 30s on RTX 4090  │
         │  2048²⁴ combinations = brute-force physically impossible  │
         └─────────────────────────────────────────────────────────┘

---

What is stored where

Data	Location	Protected by
Master password	Nowhere — never stored	Stays in your head
Argon2id salt	vault.salt (disk)	Public — harmless without password
Encrypted Vault Key	vault.db → table vault	Layers 1 + 4
Encrypted records	vault.db → table items	Layers 2 + 3 + 4
Vault Key (unlocked)	RAM only	Layers 5 + 6
Decrypted passwords	RAM, shown in UI	Layers 6 + 7
Backup mnemonic	Paper / your memory	Never on any device

---

What is PLAIN (readable without decryption)

By design — needed for filtering without decrypting every record:

Field	Why plain
item_type	login / card / note / identity / ssh_key / server
folder_id	Folder membership
favorite, deleted	UI flags
created_at, updated_at	Timestamps
source_tag	Import label (browser profile name)
title_search_hash	HMAC-SHA256 of title

Everything else is encrypted. Title, URL, username, password, notes, SSH keys, tokens — all ciphertext at rest.

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Threat Model

Attack vector	Mitigation
Stolen vault.db	SQLCipher AES-256 + XChaCha20-Poly1305 — unreadable without password
RAM dump while locked	zeroize + mlock — keys zero-wiped on lock
RAM dump while unlocked	mlock prevents swap to disk; AEAD per-field limits exposure
Brute-force master password	Argon2id 256 MB ≈ 2-4s/attempt even on high-end GPU
Clipboard sniffing	30 s TTL + cloud clipboard sync excluded
Ransomware	Honeypot file — unauthorized writes trigger alert
Symlink attack on vault.db	lstat() + O_NOFOLLOW before open
Replay attack (browser ext.)	Unique nonce per IPC + Ed25519 signature verification
DLL hijacking (Windows)	libsodium statically linked — zero external DLLs
Browser extension XSS	connect-src 'none' CSP — zero network from extension

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Cryptographic Primitives

Key derivation:     Argon2id         libsodium  (RFC 9106 compliant)
Symmetric AEAD:     XChaCha20-Poly1305  libsodium crypto_aead_xchacha20poly1305_ietf
Search index MAC:   HMAC-SHA256      libsodium crypto_auth_hmacsha256
Database layer:     AES-256-CBC      SQLCipher (page-level)
Backup encryption:  age + Argon2id   4 GB profile
Backup integrity:   BLAKE3           content-addressed
Browser↔Desktop:    Ed25519          libsodium crypto_sign_ed25519
RNG:                OS CSPRNG        libsodium randombytes_buf()

All cryptography goes through libsodium — the most widely audited
portable crypto library. Zero home-grown crypto. Zero rand::thread_rng().

---

Key Lifetime

Master password  ──►  Argon2id KDF  ──►  Master Key
                           │                  │
                        [~2-4s]          [zeroed immediately]
                                              │
                                         3 derived keys
                                        /      |       \
                                   db_key   enc_key  search_key
                                      │        │
                                 SQLCipher  decrypt Vault Key
                                             │
                                        [Vault Key]  ◄─── lives in RAM + Keychain
                                             │              while vault is OPEN
                                        encrypt/decrypt     zeroed on lock()
                                          all records