Changed random seed generation for bitcoin.

lib/bitcoin/bitcoin_mnemonic.dart

@@ -4,23 +4,11 @@ import 'dart:typed_data';
 import 'package:crypto/crypto.dart';
 import 'package:unorm_dart/unorm_dart.dart' as unorm;
 import 'package:cryptography/cryptography.dart' as cryptography;
+import 'package:cake_wallet/core/sec_random_native.dart';
 
 const segwit = '100';
 final wordlist = englishWordlist;
 
-Uint8List randomBytes(int length, {bool secure = false}) {
-  assert(length > 0);
-
-  final random = secure ? Random.secure() : Random();
-  final ret = Uint8List(length);
-
-  for (var i = 0; i < length; i++) {
-    ret[i] = random.nextInt(256);
-  }
-
-  return ret;
-}
-
 double logBase(num x, num base) => log(x) / log(base);
 
 String mnemonicEncode(int i) {
@@ -102,14 +90,15 @@ List<bool> prefixMatches(String source, List<String> prefixes) {
   return prefixes.map((prefix) => hx.startsWith(prefix.toLowerCase())).toList();
 }
 
-String generateMnemonic({int strength = 132, String prefix = segwit}) {
+Future<String> generateMnemonic(
+    {int strength = 264, String prefix = segwit}) async {
   final wordBitlen = logBase(wordlist.length, 2).ceil();
   final wordCount = strength / wordBitlen;
   final byteCount = ((wordCount * wordBitlen).ceil() / 8).ceil();
   var result = '';
 
   do {
-    final bytes = randomBytes(byteCount);
+    final bytes = await secRandom(byteCount);
     maskBytes(bytes, strength);
     result = encode(bytes);
   } while (!prefixMatches(result, [prefix]).first);
@@ -134,7 +123,7 @@ bool matchesAnyPrefix(String mnemonic) =>
 bool validateMnemonic(String mnemonic, {String prefix = segwit}) {
   try {
     return matchesAnyPrefix(mnemonic);
-  } catch(e) {
+  } catch (e) {
     return false;
   }
 }

lib/bitcoin/bitcoin_mnemonic_is_incorrect_exception.dart

@@ -1,5 +1,5 @@
 class BitcoinMnemonicIsIncorrectException implements Exception {
   @override
   String toString() =>
-      'Bitcoin mnemonic has incorrect format. Mnemonic should contain 12 words separated by space.';
+      'Bitcoin mnemonic has incorrect format. Mnemonic should contain 24 words separated by space.';
 }

lib/bitcoin/bitcoin_wallet_service.dart

@@ -25,7 +25,7 @@ class BitcoinWalletService extends WalletService<
         type: WalletType.bitcoin, name: credentials.name);
     final wallet = BitcoinWalletBase.build(
         dirPath: dirPath,
-        mnemonic: generateMnemonic(),
+        mnemonic: await generateMnemonic(),
         password: credentials.password,
         name: credentials.name,
         walletInfo: credentials.walletInfo);
@@ -47,7 +47,7 @@ class BitcoinWalletService extends WalletService<
     final walletPath = '$walletDirPath/$name';
     final walletJSONRaw = await read(path: walletPath, password: password);
     final walletInfo = walletInfoSource.values.firstWhere(
-            (info) => info.id == WalletBase.idFor(name, WalletType.bitcoin),
+        (info) => info.id == WalletBase.idFor(name, WalletType.bitcoin),
         orElse: () => null);
     final wallet = BitcoinWalletBase.fromJSON(
         password: password,