diff --git a/packages/transport/Makefile b/packages/transport/Makefile
index ba63527b0a..a5110b3cc1 100644
--- a/packages/transport/Makefile
+++ b/packages/transport/Makefile
@@ -7,5 +7,7 @@ node_modules:
 
 build:
 	rm -rf dist
-	mkdir -p dist
+	cp -r src/ dist
+	find dist/ -type f ! -name '*.js' | xargs -I {} rm {}
+	find dist/ -name '*.js' | xargs -I {} mv {} {}.flow
 	`npm bin`/browserify src/index.js > dist/index.js
diff --git a/packages/transport/dist/defered.js.flow b/packages/transport/dist/defered.js.flow
new file mode 100644
index 0000000000..7bd35cbd06
--- /dev/null
+++ b/packages/transport/dist/defered.js.flow
@@ -0,0 +1,23 @@
+/* @flow */
+
+"use strict";
+
+export type Defered = {
+  promise: Promise<void>;
+  resolve: () => void;
+  reject: (e: Error) => void;
+};
+
+export function create(): Defered {
+  let _resolve: () => void = () => {};
+  let _reject: (e: Error) => void = (e) => {};
+  const promise = new Promise((resolve, reject) => {
+    _resolve = resolve;
+    _reject = reject;
+  });
+  return {
+    promise,
+    resolve: _resolve,
+    reject: _reject,
+  };
+}
diff --git a/packages/transport/dist/handler/index.js.flow b/packages/transport/dist/handler/index.js.flow
new file mode 100644
index 0000000000..95502e614b
--- /dev/null
+++ b/packages/transport/dist/handler/index.js.flow
@@ -0,0 +1,217 @@
+/* @flow */
+
+"use strict";
+
+import type {TrezorDeviceInfo, Transport} from '../transport';
+import {create as createDefered} from '../defered';
+import {parseConfigure} from '../protobuf/parse_protocol';
+import {verifyHexBin} from './verify';
+import {buildAndSend} from './send';
+import {receiveAndParse} from './receive';
+
+import type {Defered} from '../defered';
+import type {Messages} from '../protobuf/messages';
+
+export type MessageFromTrezor = {type: string, message: Object};
+
+// eslint-disable-next-line quotes
+const stringify = require('json-stable-stringify');
+
+type TrezorDeviceInfoWithSession = TrezorDeviceInfo & {
+  session: ?string;
+}
+
+type InternalAcquireInput = {
+  path: string;
+  previous: ?string;
+  checkPrevious: boolean;
+}
+
+type AcquireInput = {
+  path: string;
+  previous: ?string;
+} | string;
+
+function parseAcquireInput(input: AcquireInput): InternalAcquireInput {
+  // eslint-disable-next-line quotes
+  if (typeof input !== 'string') {
+    const path = input.path.toString();
+    const previous = input.previous == null ? null : input.previous.toString();
+    return {
+      path,
+      previous,
+      checkPrevious: true,
+    };
+  } else {
+    const path = input.toString();
+    return {
+      path,
+      previous: null,
+      checkPrevious: false,
+    };
+  }
+}
+
+function compare(a: TrezorDeviceInfoWithSession, b: TrezorDeviceInfoWithSession): number {
+  if (!isNaN(a.path)) {
+    return parseInt(a.path) - parseInt(b.path);
+  } else {
+    return a.path < a.path ? -1 : (a.path > a.path ? 1 : 0);
+  }
+}
+
+function timeoutPromise(delay: number): Promise<void> {
+  return new Promise((resolve) => {
+    window.setTimeout(() => resolve(), delay);
+  });
+}
+
+const ITER_MAX = 60;
+const ITER_DELAY = 500;
+
+export class Handler {
+  transport: Transport;
+  _lock: Promise<any> = Promise.resolve();
+
+  // path => promise rejecting on release
+  deferedOnRelease: {[path: string]: Defered} = {};
+
+  // path => session
+  connections: {[path: string]: string} = {};
+
+  // session => path
+  reverse: {[session: string]: string} = {};
+
+  _messages: ?Messages;
+
+  constructor(transport: Transport) {
+    this.transport = transport;
+  }
+
+  lock<X>(fn: () => (X|Promise<X>)): Promise<X> {
+    const res = this._lock.then(() => fn());
+    this._lock = res.catch(() => {});
+    return res;
+  }
+
+  enumerate(): Promise<Array<TrezorDeviceInfoWithSession>> {
+    return this.lock((): Promise<Array<TrezorDeviceInfoWithSession>> => {
+      return this.transport.enumerate().then((devices) => devices.map(device => {
+        return {
+          ...device,
+          session: this.connections[device.path],
+        };
+      })).then(devices => {
+        this._releaseDisconnected(devices);
+        return devices;
+      }).then(devices => {
+        return devices.sort(compare);
+      });
+    });
+  }
+
+  _releaseDisconnected(devices: Array<TrezorDeviceInfoWithSession>) {
+  }
+
+  _lastStringified: string = ``;
+
+  listen(old: ?Array<TrezorDeviceInfoWithSession>): Promise<Array<TrezorDeviceInfoWithSession>> {
+    const oldStringified = stringify(old);
+    const last = old == null ? this._lastStringified : oldStringified;
+    return this._runIter(0, last);
+  }
+
+  _runIter(iteration: number, oldStringified: string): Promise<Array<TrezorDeviceInfoWithSession>> {
+    return this.enumerate().then(devices => {
+      const stringified = stringify(devices);
+      if ((stringified !== oldStringified) || (iteration === ITER_MAX)) {
+        this._lastStringified = stringified;
+        return devices;
+      }
+      return timeoutPromise(ITER_DELAY).then(() => this._runIter(iteration + 1, stringified));
+    });
+  }
+
+  _checkAndReleaseBeforeAcquire(parsed: InternalAcquireInput): Promise<any> {
+    const realPrevious = this.connections[parsed.path];
+    if (parsed.checkPrevious) {
+      let error = false;
+      if (realPrevious == null) {
+        error = (parsed.previous != null);
+      } else {
+        error = (parsed.previous !== realPrevious);
+      }
+      if (error) {
+        throw new Error(`wrong previous session`);
+      }
+    }
+    if (realPrevious != null) {
+      const releasePromise: Promise<void> = this._realRelease(parsed.path, realPrevious);
+      return releasePromise;
+    } else {
+      return Promise.resolve();
+    }
+  }
+
+  acquire(input: AcquireInput): Promise<string> {
+    const parsed = parseAcquireInput(input);
+    return this.lock((): Promise<string> => {
+      return this._checkAndReleaseBeforeAcquire(parsed).then(() =>
+        this.transport.connect(parsed.path)
+      ).then((session: string) => {
+        this.connections[parsed.path] = session;
+        this.reverse[session] = parsed.path;
+        this.deferedOnRelease[parsed.path] = createDefered();
+        return session;
+      });
+    });
+  }
+
+  release(session: string): Promise<void> {
+    const path = this.reverse[session];
+    return this.lock(() => this._realRelease(path, session));
+  }
+
+  _realRelease(path:string, session: string): Promise<void> {
+    return this.transport.disconnect(path, session).then(() => {
+      this._releaseCleanup(session);
+    });
+  }
+
+  _releaseCleanup(session: string) {
+    const path: string = this.reverse[session];
+    delete this.reverse[session];
+    delete this.connections[path];
+    this.deferedOnRelease[path].reject(new Error(`Device released or disconnected`));
+    return;
+  }
+
+  configure(signedData: string): Promise<void> {
+    return verifyHexBin(signedData).then((data: Buffer): Messages => {
+      return parseConfigure(data);
+    }).then((messages: Messages) => {
+      this._messages = messages;
+      return;
+    });
+  }
+
+  _sendTransport(session: string): (data: ArrayBuffer) => Promise<void> {
+    const path: string = this.reverse[session];
+    return (data) => this.transport.send(path, session, data);
+  }
+
+  _receiveTransport(session: string): () => Promise<ArrayBuffer> {
+    const path: string = this.reverse[session];
+    return () => this.transport.receive(path, session);
+  }
+
+  call(session: string, name: string, data: Object): Promise<MessageFromTrezor> {
+    if (this._messages == null) {
+      return Promise.reject(new Error(`Handler not configured.`));
+    }
+    const messages = this._messages;
+    return buildAndSend(messages, this._sendTransport(session), name, data).then(() => {
+      return receiveAndParse(messages, this._receiveTransport(session));
+    });
+  }
+}
diff --git a/packages/transport/dist/handler/receive.js.flow b/packages/transport/dist/handler/receive.js.flow
new file mode 100644
index 0000000000..a22aa90eb4
--- /dev/null
+++ b/packages/transport/dist/handler/receive.js.flow
@@ -0,0 +1,112 @@
+/* @flow */
+
+"use strict";
+
+// Logic of recieving data from trezor
+// Logic of "call" is broken to two parts - sending and recieving
+
+import {MessageDecoder} from "../protobuf/message_decoder.js";
+import {ByteBuffer} from "protobufjs";
+import type {Messages} from "../protobuf/messages.js";
+import type {MessageFromTrezor} from "./index";
+
+const MESSAGE_HEADER_BYTE: number = 0x23;
+
+// input that might or might not be fully parsed yet
+class PartiallyParsedInput {
+  // Message type number
+  typeNumber: number;
+  // Expected length of the raq message, in bytes
+  expectedLength: number;
+  // Buffer with the beginning of message; can be non-complete and WILL be modified
+  // during the object's lifetime
+  buffer: ByteBuffer;
+  constructor(typeNumber: number, length: number) {
+    this.typeNumber = typeNumber;
+    this.expectedLength = length;
+    this.buffer = new ByteBuffer(length);
+  }
+  isDone(): boolean {
+    return (this.buffer.offset >= this.expectedLength);
+  }
+  append(buffer: ByteBuffer):void {
+    this.buffer.append(buffer);
+  }
+  arrayBuffer(): ArrayBuffer {
+    const byteBuffer: ByteBuffer = this.buffer;
+    byteBuffer.reset();
+    return byteBuffer.toArrayBuffer();
+  }
+}
+
+// Parses first raw input that comes from Trezor and returns some information about the whole message.
+function parseFirstInput(bytes: ArrayBuffer): PartiallyParsedInput {
+  // convert to ByteBuffer so it's easier to read
+  const byteBuffer: ByteBuffer = ByteBuffer.concat([bytes]);
+
+  // checking first two bytes
+  const sharp1: number = byteBuffer.readByte();
+  const sharp2: number = byteBuffer.readByte();
+  if (sharp1 !== MESSAGE_HEADER_BYTE || sharp2 !== MESSAGE_HEADER_BYTE) {
+    throw new Error(`Didn't receive expected header signature.`);
+  }
+
+  // reading things from header
+  const type: number = byteBuffer.readUint16();
+  const length: number = byteBuffer.readUint32();
+
+  // creating a new buffer with the right size
+  const res: PartiallyParsedInput = new PartiallyParsedInput(type, length);
+  res.append(byteBuffer);
+  return res;
+}
+
+// If the whole message wasn't loaded in the first input, loads more inputs until everything is loaded.
+// note: the return value is not at all important since it's still the same parsedinput
+function receiveRest(
+  parsedInput: PartiallyParsedInput,
+  receiver: () => Promise<ArrayBuffer>
+): Promise<void> {
+  if (parsedInput.isDone()) {
+    return Promise.resolve();
+  }
+
+  return receiver().then((data) => {
+    // sanity check
+    if (data == null) {
+      throw new Error(`Received no data.`);
+    }
+
+    parsedInput.append(data);
+    return receiveRest(parsedInput, receiver);
+  });
+}
+
+// Receives the whole message as a raw data buffer (but without headers or type info)
+function receiveBuffer(
+  receiver: () => Promise<ArrayBuffer>
+): Promise<PartiallyParsedInput> {
+  return receiver().then((data: ArrayBuffer) => {
+    const partialInput: PartiallyParsedInput = parseFirstInput(data);
+
+    return receiveRest(partialInput, receiver).then(() => {
+      return partialInput;
+    });
+  });
+}
+
+// Reads data from device and returns decoded message, that can be sent back to trezor.js
+export function receiveAndParse(
+  messages: Messages,
+  receiver: () => Promise<ArrayBuffer>
+): Promise<MessageFromTrezor> {
+  return receiveBuffer(receiver).then((received) => {
+    const typeId: number = received.typeNumber;
+    const buffer: ArrayBuffer = received.arrayBuffer();
+    const decoder: MessageDecoder = new MessageDecoder(messages, typeId, buffer);
+    return {
+      message: decoder.decodedJSON(),
+      type: decoder.messageName(),
+    };
+  });
+}
diff --git a/packages/transport/dist/handler/send.js.flow b/packages/transport/dist/handler/send.js.flow
new file mode 100644
index 0000000000..fda63f1110
--- /dev/null
+++ b/packages/transport/dist/handler/send.js.flow
@@ -0,0 +1,152 @@
+/* @flow */
+
+"use strict";
+
+// Logic of sending data to trezor
+//
+// Logic of "call" is broken to two parts - sending and recieving
+
+import * as ProtoBuf from "protobufjs";
+import {ByteBuffer} from "protobufjs";
+import type {Messages} from "../protobuf/messages.js";
+
+const HEADER_SIZE = 1 + 1 + 4 + 2;
+const MESSAGE_HEADER_BYTE: number = 0x23;
+const BUFFER_SIZE: number = 63;
+
+// Sends more buffers to device.
+function sendBuffers(
+  sender: (data: ArrayBuffer) => Promise<void>,
+  buffers: Array<ArrayBuffer>
+): Promise<void> {
+  return buffers.reduce((prevPromise: Promise<void>, buffer: ArrayBuffer) => {
+    return prevPromise.then(() => {
+      return sender(buffer);
+    });
+  }, Promise.resolve());
+}
+
+// already built PB message
+class BuiltMessage {
+  message: ProtoBuf.Builder.Message;
+  type: number;
+
+  constructor(messages: Messages, // Builders, generated by reading config
+    name: string, // Name of the message
+    data: Object // data as "pure" object, from trezor.js
+  ) {
+    const Builder = messages.messagesByName[name];
+    if (Builder == null) {
+      throw new Error(`The message name ${name} is not found.`);
+    }
+
+    // cleans up stuff from angular and remove "null" that crashes in builder
+    cleanupInput(data);
+
+    if (data) {
+      this.message = new Builder(data);
+    } else {
+      this.message = new Builder();
+    }
+
+    this.type = messages.messageTypes[`MessageType_${name}`];
+  }
+
+  // encodes into "raw" data, but it can be too long and needs to be split into
+  // smaller buffers
+  _encodeLong(): Uint8Array {
+    const headerSize: number = HEADER_SIZE; // should be 8
+    const bytes: Uint8Array = new Uint8Array(this.message.encodeAB());
+    const fullSize: number = headerSize + bytes.length;
+
+    const encodedByteBuffer = new ByteBuffer(fullSize);
+
+    // first encode header
+
+    // 2*1 byte
+    encodedByteBuffer.writeByte(MESSAGE_HEADER_BYTE);
+    encodedByteBuffer.writeByte(MESSAGE_HEADER_BYTE);
+
+    // 2 bytes
+    encodedByteBuffer.writeUint16(this.type);
+
+    // 4 bytes (so 8 in total)
+    encodedByteBuffer.writeUint32(bytes.length);
+
+    // then put in the actual message
+    encodedByteBuffer.append(bytes);
+
+    // and convert to uint8 array
+    // (it can still be too long to send though)
+    const encoded: Uint8Array = new Uint8Array(encodedByteBuffer.buffer);
+
+    return encoded;
+  }
+
+  // encodes itself and splits into "nice" chunks
+  encode(): Array<ArrayBuffer> {
+    const bytes: Uint8Array = this._encodeLong();
+
+    const result: Array<ArrayBuffer> = [];
+    const size: number = BUFFER_SIZE;
+
+    // How many pieces will there actually be
+    const count: number = Math.floor((bytes.length - 1) / size) + 1;
+
+    // slice and dice
+    for (let i = 0; i < count; i++) {
+      const slice: Uint8Array = bytes.subarray(i * size, (i + 1) * size);
+      const newArray: Uint8Array = new Uint8Array(size);
+      newArray.set(slice);
+      result.push(newArray.buffer);
+    }
+
+    return result;
+  }
+}
+
+// Removes $$hashkey from angular and remove nulls
+function cleanupInput(message: Object): void {
+  delete message.$$hashKey;
+
+  for (const key in message) {
+    const value = message[key];
+    if (value == null) {
+      delete message[key];
+    } else {
+      if (Array.isArray(value)) {
+        value.forEach((i) => {
+          if (typeof i === `object`) {
+            cleanupInput(i);
+          }
+        });
+      }
+      if (typeof value === `object`) {
+        cleanupInput(value);
+      }
+    }
+  }
+}
+
+// Builds buffers to send.
+// messages: Builders, generated by reading config
+// name: Name of the message
+// data: Data to serialize, exactly as given by trezor.js
+// Returning buffers that will be sent to Trezor
+function buildBuffers(messages: Messages, name: string, data: Object): Array<ArrayBuffer> {
+  const message: BuiltMessage = new BuiltMessage(messages, name, data);
+  const encoded: Array<ArrayBuffer> = message.encode();
+  return encoded;
+}
+
+// Sends message to device.
+// Resolves iff everything gets sent
+export function buildAndSend(
+  messages: Messages,
+  sender: (data: ArrayBuffer) => Promise<void>,
+  name: string,
+  data: Object
+): Promise<void> {
+  const buffers: Array<ArrayBuffer> = buildBuffers(messages, name, data);
+  return sendBuffers(sender, buffers);
+}
diff --git a/packages/transport/dist/handler/verify.js.flow b/packages/transport/dist/handler/verify.js.flow
new file mode 100644
index 0000000000..fa43732ecd
--- /dev/null
+++ b/packages/transport/dist/handler/verify.js.flow
@@ -0,0 +1,52 @@
+/* @flow */
+
+"use strict";
+
+// Module for verifying ECDSA signature of configuration.
+
+import {ECPair, ECSignature, crypto} from "bitcoinjs-lib";
+
+import BigInteger from "bigi";
+
+/* eslint-disable quotes */
+const SATOSHI_KEYS: Array<string> = [
+  '\x04\xd5\x71\xb7\xf1\x48\xc5\xe4\x23\x2c\x38\x14\xf7\x77\xd8\xfa\xea\xf1\xa8\x42\x16\xc7\x8d\x56\x9b\x71\x04\x1f\xfc\x76\x8a\x5b\x2d\x81\x0f\xc3\xbb\x13\x4d\xd0\x26\xb5\x7e\x65\x00\x52\x75\xae\xde\xf4\x3e\x15\x5f\x48\xfc\x11\xa3\x2e\xc7\x90\xa9\x33\x12\xbd\x58',
+  '\x04\x63\x27\x9c\x0c\x08\x66\xe5\x0c\x05\xc7\x99\xd3\x2b\xd6\xba\xb0\x18\x8b\x6d\xe0\x65\x36\xd1\x10\x9d\x2e\xd9\xce\x76\xcb\x33\x5c\x49\x0e\x55\xae\xe1\x0c\xc9\x01\x21\x51\x32\xe8\x53\x09\x7d\x54\x32\xed\xa0\x6b\x79\x20\x73\xbd\x77\x40\xc9\x4c\xe4\x51\x6c\xb1',
+  '\x04\x43\xae\xdb\xb6\xf7\xe7\x1c\x56\x3f\x8e\xd2\xef\x64\xec\x99\x81\x48\x25\x19\xe7\xef\x4f\x4a\xa9\x8b\x27\x85\x4e\x8c\x49\x12\x6d\x49\x56\xd3\x00\xab\x45\xfd\xc3\x4c\xd2\x6b\xc8\x71\x0d\xe0\xa3\x1d\xbd\xf6\xde\x74\x35\xfd\x0b\x49\x2b\xe7\x0a\xc7\x5f\xde\x58',
+  '\x04\x87\x7c\x39\xfd\x7c\x62\x23\x7e\x03\x82\x35\xe9\xc0\x75\xda\xb2\x61\x63\x0f\x78\xee\xb8\xed\xb9\x24\x87\x15\x9f\xff\xed\xfd\xf6\x04\x6c\x6f\x8b\x88\x1f\xa4\x07\xc4\xa4\xce\x6c\x28\xde\x0b\x19\xc1\xf4\xe2\x9f\x1f\xcb\xc5\xa5\x8f\xfd\x14\x32\xa3\xe0\x93\x8a',
+  '\x04\x73\x84\xc5\x1a\xe8\x1a\xdd\x0a\x52\x3a\xdb\xb1\x86\xc9\x1b\x90\x6f\xfb\x64\xc2\xc7\x65\x80\x2b\xf2\x6d\xbd\x13\xbd\xf1\x2c\x31\x9e\x80\xc2\x21\x3a\x13\x6c\x8e\xe0\x3d\x78\x74\xfd\x22\xb7\x0d\x68\xe7\xde\xe4\x69\xde\xcf\xbb\xb5\x10\xee\x9a\x46\x0c\xda\x45',
+];
+/* eslint-enable */
+
+const keys: Array<Buffer> = SATOSHI_KEYS.map(key => new Buffer(key, `binary`));
+
+// Verifies ECDSA signature
+// pubkeys - Public keys
+// signature - ECDSA signature (concatenated R and S, both 32 bytes)
+// data - Data that are signed
+// returns True, iff the signature is correct with any of the pubkeys
+function verify(pubkeys: Array<Buffer>, bsignature: Buffer, data: Buffer): boolean {
+  const r = BigInteger.fromBuffer(bsignature.slice(0, 32));
+  const s = BigInteger.fromBuffer(bsignature.slice(32));
+  const signature = new ECSignature(r, s);
+
+  const hash = crypto.sha256(data);
+
+  return pubkeys.some(pubkey => {
+    const pair = ECPair.fromPublicKeyBuffer(pubkey);
+    return pair.verify(hash, signature);
+  });
+}
+
+// Verifies if a given data is a correctly signed config
+// Returns the data, if correctly signed, else reject
+export function verifyHexBin(data: string): Promise<Buffer> {
+  const signature = new Buffer(data.slice(0, 64 * 2), `hex`);
+  const dataB = new Buffer(data.slice(64 * 2), `hex`);
+  const verified = verify(keys, signature, dataB);
+  if (!verified) {
+    return Promise.reject(`Not correctly signed.`);
+  } else {
+    return Promise.resolve(dataB);
+  }
+}
diff --git a/packages/transport/dist/index.js.flow b/packages/transport/dist/index.js.flow
new file mode 100644
index 0000000000..b8bcf3b314
--- /dev/null
+++ b/packages/transport/dist/index.js.flow
@@ -0,0 +1,6 @@
+/* @flow */
+
+import {Handler} from './handler';
+
+// not sure how to do this in ES6 syntax, so I won't
+module.exports = Handler;
diff --git a/packages/transport/dist/protobuf/config_proto_compiled.js.flow b/packages/transport/dist/protobuf/config_proto_compiled.js.flow
new file mode 100644
index 0000000000..eeb883ec69
--- /dev/null
+++ b/packages/transport/dist/protobuf/config_proto_compiled.js.flow
@@ -0,0 +1,1059 @@
+/*
+ re-build this by:
+
+sed 's/\(google\/protobuf\)/\.\/\1/' trezor-common/protob/config.proto > trezor-common/protob/config_fixed.proto
+$(npm bin)/proto2js trezor-common/protob/config_fixed.proto -commonjs > config_proto_compiled.js
+rm trezor-common/protob/config_fixed.proto
+
+given trezor-common is from github trezor-common
+
+the config.proto is not changed much
+
+*/
+module.exports = require("protobufjs").newBuilder({})["import"]({
+    "package": null,
+    "messages": [
+        {
+            "name": "DeviceDescriptor",
+            "fields": [
+                {
+                    "rule": "optional",
+                    "options": {},
+                    "type": "uint32",
+                    "name": "vendor_id",
+                    "id": 1
+                },
+                {
+                    "rule": "optional",
+                    "options": {},
+                    "type": "uint32",
+                    "name": "product_id",
+                    "id": 2
+                },
+                {
+                    "rule": "optional",
+                    "options": {},
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+                            "enums": [],
+                            "messages": [],
+                            "options": {},
+                            "oneofs": {}
+                        }
+                    ],
+                    "options": {},
+                    "oneofs": {}
+                },
+                {
+                    "name": "SourceCodeInfo",
+                    "fields": [
+                        {
+                            "rule": "repeated",
+                            "options": {},
+                            "type": "Location",
+                            "name": "location",
+                            "id": 1
+                        }
+                    ],
+                    "enums": [],
+                    "messages": [
+                        {
+                            "name": "Location",
+                            "fields": [
+                                {
+                                    "rule": "repeated",
+                                    "options": {
+                                        "packed": true
+                                    },
+                                    "type": "int32",
+                                    "name": "path",
+                                    "id": 1
+                                },
+                                {
+                                    "rule": "repeated",
+                                    "options": {
+                                        "packed": true
+                                    },
+                                    "type": "int32",
+                                    "name": "span",
+                                    "id": 2
+                                },
+                                {
+                                    "rule": "optional",
+                                    "options": {},
+                                    "type": "string",
+                                    "name": "leading_comments",
+                                    "id": 3
+                                },
+                                {
+                                    "rule": "optional",
+                                    "options": {},
+                                    "type": "string",
+                                    "name": "trailing_comments",
+                                    "id": 4
+                                }
+                            ],
+                            "enums": [],
+                            "messages": [],
+                            "options": {},
+                            "oneofs": {}
+                        }
+                    ],
+                    "options": {},
+                    "oneofs": {}
+                }
+            ],
+            "enums": [],
+            "imports": [],
+            "options": {
+                "java_package": "com.google.protobuf",
+                "java_outer_classname": "DescriptorProtos",
+                "optimize_for": "SPEED"
+            },
+            "services": []
+        }
+    ],
+    "options": {},
+    "services": []
+}).build();
diff --git a/packages/transport/dist/protobuf/message_decoder.js.flow b/packages/transport/dist/protobuf/message_decoder.js.flow
new file mode 100644
index 0000000000..0212dc496e
--- /dev/null
+++ b/packages/transport/dist/protobuf/message_decoder.js.flow
@@ -0,0 +1,102 @@
+/* @flow */
+
+"use strict";
+
+// Helper module for converting Trezor's raw input to
+// ProtoBuf's message and from there to regular JSON to trezor.js
+
+import * as ProtoBuf from "protobufjs";
+import {ByteBuffer, Long} from "protobufjs";
+
+import {Messages} from "./messages.js";
+
+export class MessageDecoder {
+  // Builders, generated by reading config
+  messages: Messages;
+  // message type number
+  type: number;
+  // raw data to push to Trezor
+  data: ArrayBuffer;
+
+  constructor(messages: Messages, type: number, data: ArrayBuffer) {
+    this.type = type;
+    this.data = data;
+    this.messages = messages;
+  }
+
+  // Returns an info about this message,
+  // which includes the constructor object and a name
+  _messageInfo() : MessageInfo {
+    const r = this.messages.messagesByType[this.type];
+    if (r == null) {
+      throw new Error(`Method type not found`, this.type);
+    }
+    return new MessageInfo(r.constructor, r.name);
+  }
+
+  // Returns the name of the message
+  messageName() : string {
+    return this._messageInfo().name;
+  }
+
+  // Returns the actual decoded message, as a ProtoBuf.js object
+  _decodedMessage() : ProtoBuf.Builder.Message {
+    const constructor = this._messageInfo().messageConstructor;
+    return constructor.decode(this.data);
+  }
+
+  // Returns the message decoded to JSON, that could be handed back
+  // to trezor.js
+  decodedJSON() : Object {
+    const decoded = this._decodedMessage();
+    const converted = messageToJSON(decoded);
+
+    return JSON.parse(JSON.stringify(converted));
+  }
+}
+
+class MessageInfo {
+  messageConstructor: ProtoBuf.Builder.Message;
+  name: string;
+  constructor(messageConstructor: ProtoBuf.Builder.Message, name: string) {
+    this.messageConstructor = messageConstructor;
+    this.name = name;
+  }
+}
+
+// Converts any ProtoBuf message to JSON in Trezor.js-friendly format
+function messageToJSON(message: ProtoBuf.Builder.Message) : Object {
+  const res = {};
+  const meta = message.$type;
+
+  for (const key in message) {
+    const value = message[key];
+    if (typeof value === `function`) {
+      // ignoring
+    } else if (value instanceof ByteBuffer) {
+      const hex = value.toHex();
+      res[key] = hex;
+    } else if (value instanceof Long) {
+      const num = value.toNumber();
+      res[key] = num;
+    } else if (Array.isArray(value)) {
+      const decodedArr = value.map((i) => {
+        if (typeof i === `object`) {
+          return messageToJSON(i);
+        } else {
+          return i;
+        }
+      });
+      res[key] = decodedArr;
+    } else if (value instanceof ProtoBuf.Builder.Message) {
+      res[key] = messageToJSON(value);
+    } else if (meta._fieldsByName[key].type.name === `enum`) {
+      const enumValues = meta._fieldsByName[key].resolvedType.getChildren();
+      res[key] = enumValues.find(e => e.id === value).name;
+    } else {
+      res[key] = value;
+    }
+  }
+  return res;
+}
+
diff --git a/packages/transport/dist/protobuf/messages.js.flow b/packages/transport/dist/protobuf/messages.js.flow
new file mode 100644
index 0000000000..9c8da7f631
--- /dev/null
+++ b/packages/transport/dist/protobuf/messages.js.flow
@@ -0,0 +1,34 @@
+/* @flow */
+
+"use strict";
+
+// This is a simple class that represents information about messages,
+// as they are loaded from the protobuf definition,
+// so they are understood by both sending and recieving code.
+
+import * as ProtoBuf from "protobufjs";
+
+type MessageArray<KeyType> = { [key: KeyType]: ProtoBuf.Bulder.Message };
+
+export class Messages {
+  messagesByName: MessageArray<string>;
+  messagesByType: MessageArray<number>;
+  messageTypes: { [key: string]: number };
+
+  constructor(messages: MessageArray<string>) {
+    this.messagesByName = messages;
+
+    const messagesByType: MessageArray<number> = {};
+    Object.keys(messages.MessageType).forEach(longName => {
+      const typeId = messages.MessageType[longName];
+      const shortName = longName.split(`_`)[1];
+      messagesByType[typeId] = {
+        name: shortName,
+        constructor: messages[shortName],
+      };
+    });
+    this.messagesByType = messagesByType;
+    this.messageTypes = messages.MessageType;
+  }
+}
+
diff --git a/packages/transport/dist/protobuf/parse_protocol.js.flow b/packages/transport/dist/protobuf/parse_protocol.js.flow
new file mode 100644
index 0000000000..36e310d491
--- /dev/null
+++ b/packages/transport/dist/protobuf/parse_protocol.js.flow
@@ -0,0 +1,30 @@
+/* @flow */
+
+"use strict";
+
+// Module for loading the protobuf description from serialized description
+
+import * as ProtoBuf from "protobufjs";
+
+import {Messages} from "./messages.js";
+import {protocolToJSON} from "./to_json.js";
+import * as compiledConfigProto from "./config_proto_compiled.js";
+
+// Parse configure data (it has to be already verified)
+export function parseConfigure(data: Buffer): Messages {
+  const configBuilder = compiledConfigProto[`Configuration`];
+  const loadedConfig = configBuilder.decode(data);
+
+  const validUntil = loadedConfig.valid_until;
+  const timeNow = Math.floor(Date.now() / 1000);
+  if (timeNow >= validUntil) {
+    throw new Error(`Config too old; ` + timeNow + ` >= ` + validUntil);
+  }
+
+  const wireProtocol = loadedConfig.wire_protocol;
+  const protocolJSON = protocolToJSON(wireProtocol.toRaw());
+  const protobufMessages = ProtoBuf.newBuilder({})[`import`](protocolJSON).build();
+
+  return new Messages(protobufMessages);
+}
+
diff --git a/packages/transport/dist/protobuf/to_json.js.flow b/packages/transport/dist/protobuf/to_json.js.flow
new file mode 100644
index 0000000000..0d53b3d471
--- /dev/null
+++ b/packages/transport/dist/protobuf/to_json.js.flow
@@ -0,0 +1,121 @@
+/* @flow */
+
+"use strict";
+
+// Helper module that does conversion from already parsed protobuf's
+// FileDescriptorSet to JSON, that can be used to initialize ProtoBuf.js
+//
+// Theoretically this should not be necessary, since FileDescriptorSet is protobuf "native" description,
+// but ProtoBuf.js does NOT know how to make Builder from FileDescriptorSet, but it can build it from JSON.
+// See https://github.com/dcodeIO/ProtoBuf.js/issues/250
+//
+// This conversion is probably not very stable and does not "scale" that well, since it's
+// intended just for our relatively small usecase.
+// But it works here.
+
+import {shim} from 'object.values';
+if (!Object.values) {
+  shim();
+}
+
+export function protocolToJSON(p: any): Object {
+  // TODO: what if there are more files?
+  const res = fileToJSON(p.file[2]);
+  res.imports = [fileToJSON(p.file[1])];
+  return res;
+}
+
+function fileToJSON(f: any): Object {
+  const res = {};
+  res.package = f.package;
+  res.options = f.options;
+  res.services = [];
+  const messagesSimple = Object.values(f.message_type).map(messageToJSON);
+  const messagesRef = extensionToJSON(f.extension);
+  res.messages = messagesRef.concat(messagesSimple);
+  res.enums = Object.values(f.enum_type).map(enumToJSON);
+  return res;
+}
+
+function enumToJSON(enumm: any): Object {
+  const res = {};
+  res.name = enumm.name;
+  res.values = Object.values(enumm.value).map(enum_valueToJSON);
+  res.options = {};
+  return res;
+}
+
+function extensionToJSON(extensions: {[key: string]: any}): Array<any> {
+  const res = {};
+  Object.values(extensions).forEach(function (extension: any) {
+    const extendee = extension.extendee.slice(1);
+    if (res[extendee] == null) {
+      res[extendee] = {};
+      res[extendee].ref = extendee;
+      res[extendee].fields = [];
+    }
+    res[extendee].fields.push(fieldToJSON(extension));
+  });
+  return Object.values(res);
+}
+
+function enum_valueToJSON(val: any): Object {
+  const res = {};
+  res.name = val.name;
+  res.id = val.number;
+  return res;
+}
+
+function messageToJSON(message: any): Object {
+  const res = {};
+  res.enums = [];
+  res.name = message.name;
+  res.options = message.options || {};
+  res.messages = [];
+  res.fields = Object.values(message.field).map(fieldToJSON);
+  res.oneofs = {};
+  return res;
+}
+
+const type_map = {
+  "1": `double`,
+  "2": `float`,
+  "3": `int64`,
+  "4": `uint64`,
+  "5": `int32`,
+  "6": `fixed64`,
+  "7": `fixed32`,
+  "8": `bool`,
+  "9": `string`,
+  "10": `group`,
+  "11": `message`,
+  "12": `bytes`,
+  "13": `uint32`,
+  "14": `enum`,
+  "15": `sfixed32`,
+  "16": `sfixed64`,
+  "17": `sint32`,
+  "18": `sint64`,
+};
+
+function fieldToJSON(field: any): Object {
+  const res = {};
+  if (field.label === 1) {
+    res.rule = `optional`;
+  }
+  if (field.label === 2) {
+    res.rule = `required`;
+  }
+  if (field.label === 3) {
+    res.rule = `repeated`;
+  }
+  res.type = type_map[field.type];
+  if (field.type_name) {
+    res.type = field.type_name.slice(1);
+  }
+  res.name = field.name;
+  res.options = field.options || {};
+  res.id = field.number;
+  return res;
+}
+
diff --git a/packages/transport/dist/transport.js.flow b/packages/transport/dist/transport.js.flow
new file mode 100644
index 0000000000..a9cd31ef5e
--- /dev/null
+++ b/packages/transport/dist/transport.js.flow
@@ -0,0 +1,17 @@
+/* @flow */
+
+"use strict";
+
+// does not have session
+export type TrezorDeviceInfo = {
+  path: string;
+}
+
+export type Transport = {
+  enumerate: () => Promise<Array<TrezorDeviceInfo>>;
+  send: (path: string, session: string, data: ArrayBuffer) => Promise<void>;
+  receive: (path: string, session: string) => Promise<ArrayBuffer>;
+  connect: (path: string) => Promise<string>;
+  disconnect: (path: string, session: string) => Promise<void>;
+}
+