/*
Web worker processing
function processMessage(event) {
            var data = event['data'];
            var type = data['type'];

            switch (type) {
            case 'deriveAddressRange':
                var addresses = deriveAddressRange(
                    data['node'],
                    data['firstIndex'],
                    data['lastIndex'],
                    data['version'],
                    data['addressFormat']
                );
                self.postMessage({
                    'addresses': addresses,
                    'firstIndex': data['firstIndex'],
                    'lastIndex': data['lastIndex'],
                    'i': data['i']
                });
                break;
            case 'deriveNode':
                var node = deriveNode(
                    data['xpub'],
                    data['index'],
                    data['version']
                );
                self.postMessage({
                    'xpub': node,
                    'i': data['i']
                });
                break;
            default:
                throw new Error('Unknown message type: ' + type);
            }
        }