Cache BIP85 derivations and incremental snapshots

src/nostr/snapshot.py

@@ -59,7 +59,18 @@ class SnapshotHandler:
         await self.ensure_manifest_is_current()
         await self._connect_async()
         manifest, chunks = prepare_snapshot(encrypted_bytes, limit)
+
+        existing: dict[str, str] = {}
+        if self.current_manifest:
+            for old in self.current_manifest.chunks:
+                if old.hash and old.event_id:
+                    existing[old.hash] = old.event_id
+
         for meta, chunk in zip(manifest.chunks, chunks):
+            cached_id = existing.get(meta.hash)
+            if cached_id:
+                meta.event_id = cached_id
+                continue
             content = base64.b64encode(chunk).decode("utf-8")
             builder = nostr_client.EventBuilder(
                 nostr_client.Kind(KIND_SNAPSHOT_CHUNK), content

src/seedpass/core/manager.py

@@ -180,6 +180,7 @@ class PasswordManager:
         self.error_queue: queue.Queue[Exception] = queue.Queue()
         self._current_notification: Optional[Notification] = None
         self._notification_expiry: float = 0.0
+        self._bip85_cache: dict[tuple[int, int], bytes] = {}
 
         # Track changes to trigger periodic Nostr sync
         self.is_dirty: bool = False
@@ -212,6 +213,20 @@ class PasswordManager:
                 self.fingerprint_manager.get_current_fingerprint_dir()
             )
 
+    def get_bip85_entropy(self, purpose: int, index: int, bytes_len: int = 32) -> bytes:
+        """Return deterministic entropy via the cached BIP-85 function."""
+
+        if self.bip85 is None:
+            raise RuntimeError("BIP-85 is not initialized")
+        return self.bip85.derive_entropy(
+            index=index, bytes_len=bytes_len, app_no=purpose
+        )
+
+    def clear_bip85_cache(self) -> None:
+        """Clear the internal BIP-85 cache."""
+
+        self._bip85_cache.clear()
+
     def ensure_script_checksum(self) -> None:
         """Initialize or verify the checksum of the manager script."""
         script_path = Path(__file__).resolve()
@@ -1173,7 +1188,20 @@ class PasswordManager:
         try:
             seed_bytes = Bip39SeedGenerator(self.parent_seed).Generate()
             self.bip85 = BIP85(seed_bytes)
+            self._bip85_cache = {}
+            orig_derive = self.bip85.derive_entropy
+
+            def cached_derive(index: int, bytes_len: int, app_no: int = 39) -> bytes:
+                key = (app_no, index)
+                if key not in self._bip85_cache:
+                    self._bip85_cache[key] = orig_derive(
+                        index=index, bytes_len=bytes_len, app_no=app_no
+                    )
+                return self._bip85_cache[key]
+
+            self.bip85.derive_entropy = cached_derive
             logging.debug("BIP-85 initialized successfully.")
+            self.clear_bip85_cache()
         except Exception as e:
             logging.error(f"Failed to initialize BIP-85: {e}", exc_info=True)
             print(colored(f"Error: Failed to initialize BIP-85: {e}", "red"))