newFile method
Implementation
Future<(UVaultHeader, UAead)> newFile({int chunkSize = defaultVaultChunkSize}) async {
final Uint8List fileKey = uRandomBytes(32);
final Uint8List wrapNonce = uRandomBytes(12);
final Uint8List wrapped = Uint8List.fromList(<int>[...wrapNonce, ...await _master.seal(wrapNonce, fileKey)]);
final UAead aead = await _backend.aead(fileKey);
return (UVaultHeader(algorithmId: aead.algorithmId, chunkSize: chunkSize, noncePrefix: uRandomBytes(7), wrappedKey: wrapped), aead);
}