feat(spv): verify Merkle proofs progressively, gate spendability on it
Balance/history now render as soon as tx downloads finish instead of blocking on every historical Merkle proof, critical for mobile where proof-checking can take much longer than the download itself. Proofs continue to be checked in the background and each tx's Verified flag catches up progressively; header ranges are now fetched in batches (blockchain.block.headers) instead of one call per header to keep this fast over high-latency links. Coin selection (UtxoSpendability.IsSpendable) refuses to spend a UTXO until its Merkle proof is actually checked, regardless of confirmation count, so a server that fabricates a confirmed balance can get it displayed early but never spent before the forgery is caught. The disk cache only ever persists the fully-verified end state of a sync. UI surfaces the new PendingVerificationSats/SpendableSats split with a "verifying..." badge, and the sync save now runs off the UI thread to avoid freezing on slower hardware.
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@@ -28,6 +28,9 @@ public partial class MainWindowViewModel
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[ObservableProperty]
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private string immatureText = "";
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[ObservableProperty]
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private string verifyingText = "";
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[ObservableProperty]
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private string networkInfo = "";
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@@ -253,6 +256,7 @@ public partial class MainWindowViewModel
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BalanceText = $"0.00000000 {Profile.CoinUnit}";
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UnconfirmedText = "";
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ImmatureText = "";
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VerifyingText = "";
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ReceiveAddress = _account.GetReceiveAddress(0).ToString();
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History.Clear();
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Addresses.Clear();
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@@ -265,7 +269,11 @@ public partial class MainWindowViewModel
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$"m/{_doc!.AccountPath}/0/{i}"));
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return;
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}
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BalanceText = Fmt(cache.ConfirmedSats - cache.ImmatureSats);
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// Not "Confirmed - Immature - PendingVerification": those two can overlap (an
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// immature coinbase can also be unverified), which double-subtracts and can go
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// negative. SpendableSats is computed directly from the same IsSpendable gate
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// coin selection uses, so it's always correct.
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BalanceText = Fmt(cache.SpendableSats);
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var pending = cache.History.Where(t => t.Height <= 0).Sum(t => t.DeltaSats);
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UnconfirmedText = pending != 0
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? $"{Loc.Tr("msg.pending")}: {(pending > 0 ? "+" : "")}{Fmt(pending)} — {Loc.Tr("msg.notspendable")}"
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@@ -273,13 +281,20 @@ public partial class MainWindowViewModel
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ImmatureText = cache.ImmatureSats != 0
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? $"{Loc.Tr("msg.immature")}: {Fmt(cache.ImmatureSats)} — {Loc.Tr("msg.notspendable")}"
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: "";
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// Progressive verification (§7.4): funds confirmed by the server but whose Merkle
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// proof background verification hasn't reached yet — same "not spendable" treatment
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// as immature/pending, distinct wording so it doesn't read as a maturity/confirmation problem.
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VerifyingText = cache.PendingVerificationSats != 0
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? $"{Loc.Tr("msg.verifying")}: {Fmt(cache.PendingVerificationSats)} — {Loc.Tr("msg.notspendable")}"
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: "";
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ReceiveAddress = _account.GetReceiveAddress(cache.NextReceiveIndex).ToString();
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History.Clear();
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foreach (var tx in cache.History)
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History.Add(new HistoryRow(
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tx.Height > 0 ? tx.Height.ToString() : "mempool",
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(tx.DeltaSats >= 0 ? "+" : "") + Fmt(tx.DeltaSats, withLabel: false),
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tx.Txid));
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tx.Txid,
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tx.Verified));
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Addresses.Clear();
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foreach (var a in cache.Addresses)
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@@ -273,32 +273,34 @@ public partial class MainWindowViewModel
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_doc.Cache?.NextChangeIndex ?? 0,
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net);
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_synchronizer.Progress += msg => Dispatcher.UIThread.Post(() => StatusMessage = msg);
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// Progressive verification (§7.4): the wallet becomes usable as soon as
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// transaction downloads finish, without waiting for every historical Merkle
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// proof — critical on mobile, where verifying thousands of proofs can take far
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// longer than the download itself. Never persisted to disk on its own (only the
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// final, fully-verified snapshot below is saved); coin selection still refuses
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// any UTXO whose proof isn't checked yet (CachedUtxo.Verified), so showing this
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// early can't be exploited to spend a server-fabricated balance.
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_synchronizer.PartialResult += r => Dispatcher.UIThread.Post(() => ApplyPartialResult(r));
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}
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do
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{
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_resyncRequested = false;
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var result = await _synchronizer.SyncOnceAsync(ct);
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// Off the UI thread: sync does heavy CPU work (LINQ over thousands of
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// cached txs/UTXOs) and blocking JSON/disk I/O between awaits, negligible
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// on desktop but enough to freeze the UI (ANR) on slower mobile hardware.
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var (result, rawHex, verifiedAt, blockHeaders) = await Task.Run(async () =>
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{
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var r = await _synchronizer.SyncOnceAsync(ct);
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var caches = _synchronizer.ExportCaches(PalladiumNetworks.For(_account.Profile.Kind));
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return (r, caches.RawTxHex, caches.VerifiedAt, caches.BlockHeaders);
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}, ct);
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_lastTransactions = result.Transactions;
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var (rawHex, verifiedAt, blockHeaders) = _synchronizer.ExportCaches(
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PalladiumNetworks.For(_account.Profile.Kind));
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_doc.Cache = new SyncCache
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{
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TipHeight = result.TipHeight,
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ConfirmedSats = result.ConfirmedSats,
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UnconfirmedSats = result.UnconfirmedSats,
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ImmatureSats = result.ImmatureSats,
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NextReceiveIndex = result.NextReceiveIndex,
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NextChangeIndex = result.NextChangeIndex,
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History = [.. result.History],
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Utxos = [.. result.Utxos],
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Addresses = [.. result.AddressRows],
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RawTxHex = rawHex,
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VerifiedAt = verifiedAt,
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BlockHeaders = blockHeaders,
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};
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WalletStore.Save(_doc, _walletPath!, _password);
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var cache = new SyncCache { RawTxHex = rawHex, VerifiedAt = verifiedAt, BlockHeaders = blockHeaders };
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FillDisplayFields(cache, result);
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_doc.Cache = cache;
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await WalletStore.SaveAsync(_doc, _walletPath!, _password);
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ApplyCache(_doc.Cache);
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_syncFailed = false;
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StatusMessage = $"{Loc.Tr("msg.synced")}: {Loc.Tr("msg.height")} {result.TipHeight}, " +
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@@ -345,6 +347,44 @@ public partial class MainWindowViewModel
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_ = ConnectAndSync();
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}
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/// <summary>
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/// Applies a provisional (not-yet-fully-verified) snapshot fired mid-sync: updates the
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/// in-memory display cache only — never persisted to disk on its own, so an interrupted
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/// sync can't leave behind a cache file whose VerifiedAt/RawTxHex/BlockHeaders (needed to
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/// resume without re-downloading) were never written.
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/// </summary>
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private void ApplyPartialResult(SyncResult result)
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{
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if (_doc is null)
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return;
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var previous = _doc.Cache;
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var cache = new SyncCache
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{
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RawTxHex = previous?.RawTxHex,
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VerifiedAt = previous?.VerifiedAt,
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BlockHeaders = previous?.BlockHeaders,
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};
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FillDisplayFields(cache, result);
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_doc.Cache = cache;
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_lastTransactions = result.Transactions;
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ApplyCache(cache);
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}
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private static void FillDisplayFields(SyncCache cache, SyncResult result)
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{
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cache.TipHeight = result.TipHeight;
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cache.ConfirmedSats = result.ConfirmedSats;
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cache.UnconfirmedSats = result.UnconfirmedSats;
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cache.ImmatureSats = result.ImmatureSats;
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cache.PendingVerificationSats = result.PendingVerificationSats;
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cache.SpendableSats = result.SpendableSats;
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cache.NextReceiveIndex = result.NextReceiveIndex;
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cache.NextChangeIndex = result.NextChangeIndex;
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cache.History = [.. result.History];
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cache.Utxos = [.. result.Utxos];
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cache.Addresses = [.. result.AddressRows];
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}
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/// <summary>
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/// Peer discovery. Always clickable: if the wallet is already connected, it reuses
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/// that connection; otherwise it opens a short-lived connection to a candidate server
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@@ -17,7 +17,7 @@ using PalladiumWallet.Core.Wallet;
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namespace PalladiumWallet.App.ViewModels;
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/// <summary>Transaction history row for the view.</summary>
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public sealed record HistoryRow(string Conferma, string Importo, string Txid);
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public sealed record HistoryRow(string Conferma, string Importo, string Txid, bool Verified = true);
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/// <summary>Address view row with pre-computed keys and derivation path.</summary>
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public sealed record AddressRow(
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@@ -102,7 +102,8 @@ public sealed class TransactionDetailsViewModel
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{
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if (d.Confirmations <= 0)
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return loc["tx.status.mempool"];
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return $"{d.Confirmations} {loc["tx.status.confirmations"]} ({loc["tx.status.block"]} {d.Height})";
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var status = $"{d.Confirmations} {loc["tx.status.confirmations"]} ({loc["tx.status.block"]} {d.Height})";
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return d.Verified ? status : $"{status} — {loc["history.unverified"]}";
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}
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private string Signed(long sats)
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