kaspa_sdk

A pure-Dart SDK for the Kaspa cryptocurrency.

Supports wallet generation, address derivation, transaction signing and submission, UTXO management, and real-time balance monitoring — with no Flutter dependency.

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Features

• BIP39 mnemonic generation and validation
• BIP32 address derivation at path m/44'/111111'/0'/0/0
• Kaspa cashaddr encoding and decoding
• Transaction building & signing — pure-Dart UTXO selection with fee convergence, BIP340 Schnorr signing, and BLAKE2b-256 sighash (KIP-9 storage mass)
• wRPC node client — JSON-RPC over WebSocket (getUtxosByAddresses, submitTransaction, getBlockDagInfo, and continuous balance stream)
• Automatic node discovery via the Kaspa public resolver network
• Mainnet and testnet-10 support

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Installation

Add to your pubspec.yaml:

dependencies:
  kaspa_sdk: ^0.1.0

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Quick Start

import 'package:kaspa_sdk/kaspa_sdk.dart';

// Generate a new wallet
final wallet = KaspaWallet.generate();
print(wallet.address); // kaspa:qp...

// Or restore from a mnemonic
final existing = KaspaWallet.fromMnemonic('abandon ability ...');

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Node Discovery

final resolver = KaspaResolverService();
final nodeUrl = await resolver.resolve(KaspaNetwork.mainnet)
    ?? KaspaNetworkConfig.mainnet.fallbackNodeUrl;

The resolver queries 16 public nodes and returns the least-loaded one. Falls back to a hardcoded URL if all resolvers are unavailable.

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Fetching Balance

final client = KaspaNodeClient(url: nodeUrl);

// One-shot fetch
final utxos = await client.getUtxosByAddresses([wallet.address]);
final totalKas = utxos.fold<double>(0, (s, u) => s + u.amountSompi / 1e8);
print('Balance: $totalKas KAS');

await client.close();

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Continuous Balance Monitoring

final client = KaspaNodeClient(url: nodeUrl);

final sub = client.watchBalance(wallet.address).listen((kas) {
  print('Balance: $kas KAS');
});

// When done
await sub.cancel();
await client.close();

watchBalance manages a persistent WebSocket connection internally and auto-reconnects on errors.

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Sending a Transaction

try {
  final txId = await wallet.sendTransaction(
    nodeUrl: nodeUrl,
    toAddress: 'kaspa:qrecipient...',
    amountSompi: 100000000, // 1 KAS = 10^8 sompi
  );
  print('Sent! txId: $txId');
  print('Explorer: ${KaspaNetworkConfig.mainnet.explorerBaseUrl}$txId');
} on InsufficientFundsException catch (e) {
  print('Not enough funds: $e');
} on KaspaException catch (e) {
  print('Transaction error: $e');
}

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Confirmation Counting

Use getBlockDagInfo to track confirmations after a payment:

final client = KaspaNodeClient(url: nodeUrl);

// Record the DAA score when payment was detected
final detected = await client.getBlockDagInfo();
final detectedDaa = detected.virtualDaaScore;

// Later, poll for current score
final current = await client.getBlockDagInfo();
final confirmations = current.virtualDaaScore - detectedDaa;
print('Confirmations: $confirmations');

await client.close();

---

Testnet-10

// Derive a testnet address
final testWallet = KaspaWallet.fromMnemonic(mnemonic, hrp: 'kaspatest');
print(testWallet.address); // kaspatest:qp...

// Find a testnet node
final testUrl = await KaspaResolverService().resolve(KaspaNetwork.testnet10)
    ?? KaspaNetworkConfig.testnet10.fallbackNodeUrl;

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Low-Level API

For advanced use cases, all cryptographic primitives are exported:

import 'package:kaspa_sdk/kaspa_sdk.dart';

// Schnorr signing
final sig = kaspaSchnorrSign(privKey32, msgHash32);

// Sighash
final hash = calcKaspaSigHash(
  txVersion: 0,
  txIds: [txId],
  indices: [0],
  utxos: [utxo],
  outputs: [output],
  inputIndex: 0,
);

// Build a transaction without sending
final result = buildSignedTransaction(
  utxoEntries: utxos,
  fromPrivKey32: privKey32,
  fromAddress: 'kaspa:qsender...',
  toAddress: 'kaspa:qrecipient...',
  amountSompi: 100000000,
);
// result.transaction is ready for submitTransaction

---

Network Configuration

final cfg = KaspaNetworkConfig.mainnet;
print(cfg.addressHrp);             // 'kaspa'
print(cfg.fallbackNodeUrl);        // 'wss://rose.kaspa.green/...'
print(cfg.symbol);                 // 'KAS'
print(cfg.explorerBaseUrl);        // 'https://kaspa.stream/transactions/'

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Platform Support

Works on all platforms that support dart:io:

Platform	Supported
Flutter (iOS, Android, macOS, Windows, Linux)	✅
Dart CLI	✅
Dart server (shelf, etc.)	✅
Flutter Web / Dart Web	❌ (requires dart:io)

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Security

• Private keys are derived in memory only and never stored by this package.
• Signing is deterministic (BIP340 with all-zero aux randomness) — no random number generator dependency for signing.
• Mnemonic validation uses BIP39 checksum verification.
• No native code, FFI, or platform channels — entirely pure Dart.

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References

• Kaspa documentation
• rusty-kaspa — the reference node implementation
• KIP-0009 — storage mass formula
• BIP-39 — mnemonic generation
• BIP-32 — hierarchical key derivation
• BIP-340 — Schnorr signatures