tests: add offline default and kdf slider

docs/SPEC.md

@@ -1,6 +1,44 @@
 # SeedPass Specification
 
+## Key Hierarchy
+
+SeedPass derives a hierarchy of keys from a single BIP-39 parent seed using HKDF:
+
+- **Master Key** – `HKDF(seed, "seedpass:v1:master")`
+- **KEY_STORAGE** – used to encrypt vault data.
+- **KEY_INDEX** – protects the metadata index.
+- **KEY_PW_DERIVE** – deterministic password generation.
+- **KEY_TOTP_DET** – deterministic TOTP secrets.
+
+Each context string keeps derived keys domain separated.
+
+## KDF Parameters
+
+Passwords are protected with **PBKDF2-HMAC-SHA256**. The default work factor is
+**50,000 iterations** but may be adjusted via the settings slider. The config
+stores a `KdfConfig` structure with the chosen iteration count, algorithm name,
+and the current spec version (`CURRENT_KDF_VERSION = 1`). Argon2 is available
+with a default `time_cost` of 2 when selected.
+
+## Message Formats
+
+SeedPass synchronizes profiles over Nostr using three event kinds:
+
+- **Manifest (`30070`)** – high level snapshot description and current version.
+- **Snapshot Chunk (`30071`)** – compressed, encrypted portions of the vault.
+- **Delta (`30072`)** – incremental changes since the last snapshot.
+
+Events encode JSON and include tags for checksums, fingerprints, and timestamps.
+
+## Versioning
+
+Configuration and KDF schemas are versioned so clients can migrate older
+profiles. Nostr events carry a version field in the manifest, and the software
+follows semantic versioning for releases.
+
 ## Memory Protection
 
-SeedPass encrypts sensitive values in memory and attempts to wipe them when no longer needed. This zeroization is best-effort only; Python's memory management may retain copies of decrypted data. Critical cryptographic operations may move to a Rust/WASM module in the future to provide stronger guarantees.
-
+SeedPass encrypts sensitive values in memory and attempts to wipe them when no
+longer needed. This zeroization is best-effort only; Python's memory management
+may retain copies of decrypted data. Critical cryptographic operations may move
+to a Rust/WASM module in the future to provide stronger guarantees.