monero-agent 3.0.4
Monero Agent
License: MIT
Requires Python: >=3.5

Monero Wallet Python implementation
===================================

|Build Status|

Pure-python Monero Wallet implementation in Python3.

Implements transaction signing protocol designed for Trezor hardware
wallet as described in
`monero-trezor-doc <https://github.com/ph4r05/monero-trezor-doc>`__.

The main purpose of this repo is to provide host side (agent) for the
transaction signing with the Trezor hardware wallet. The repo also
contains the initial implementation for the Trezor side. The Trezor
protocol side underwent heavy refactoring and is about to be merged to
the `trezor-core <https://github.com/ph4r05/trezor-core>`__ repository.

The repo provides integration tests for Trezor wallet transaction
signing.

-  PR adding Monero support to the Trezor hardware wallet (client side
   of the signing protocol):
   https://github.com/trezor/trezor-core/pull/293
-  PR adding Trezor hardware support to official Monero codebase:
   https://github.com/monero-project/monero/pull/4241

Supported features
------------------

-  Full RingCT (one UTXO)
-  Simple RingCT (more than 1 UTXOs)
-  Sub-addresses
-  Key image sync
-  Bulletproofs (batch verification, signing, ready for v9 fork)
-  Ledger protocol implementation, HW wallet side

Roadmap
-------

-  Spend proof
-  Reserver proof
-  Multisig
-  Wallet implementation (funds receiving, UTXO mixing)
-  Ledger protocol implementation, host side

Protocol
--------

In order to support RingCT on hardware wallet with limited resources a
subdivided protocol had to be implemented. It is not feasible to process
the signed transaction in one run on the hardware wallet with tens of
UTXOs and multiple outputs.

The introduction to the topic is described here:

https://github.com/ph4r05/monero-trezor-doc

The documentation can be out of sync from the code. Take this source
code as a primary reference.

In the current protocol it is assumed there may be multiple input UTXO
(tens to hundreds). So it is optimized to work incrementally, one UTXO
at a time. This is reasonable to assume as your funds may be scattered
over many small transactions. On the other hand we assume the number of
outputs is relatively small (small units) as it usually is in the Monero
transactions.

It is quite easy to extend protocol to work with large amounts of
outputs but due to the message structure which is later signed it will
be needed to add two more roundrips with sending output related data one
by one to the Trezor for incremental hashing.

Outputs are pinned in the beginning of the protocol - number of outputs
is fixed at this point in the Trezor and HMAC with unique key (index
dependent) is generated for each output. So in further roundtrips it is
assured only previously pinned outputs in the exact given order are
processed. The same principle is used for each data produced by the
Trezor which are later used as inputs.

Project structure
-----------------

Agent <-> Trezor

Agent is an object supposed to run on the host PC where Trezor is the HW
wallet implementation. ``agent.py`` and ``trezor.py`` are mainly ports
of the C++ code to the Python for PoC, experimentation and testing.
These versions are not optimized for usage in HW environment.

Optimized versions are ``agent_lite.py`` and ``trezor_lite.py``.

Currently, the agent functionality is used just for testing and as a
PoC. The Trezor support has been integrated to the official Monero
`CLI <https://github.com/monero-project/monero>`__ and
`GUI <https://github.com/monero-project/monero-gui>`__ wallets.

Serialize lib
-------------

The project depends on my ``monero-serialize`` library. Data objects
used in the Monero are defined there, it supports serialization /
deserialization to binary format. The serialized binary messages are
hashed during the transaction signature.

https://github.com/ph4r05/monero-serialize

Crypto
------

Monero uses Ed25519 elliptic curve. The pure-python implementation is
not optimized to avoid side-channel leaks (e.g., timing) as it serves
mainly as PoC.

The project uses Ed25519 implementation which works in extended Edwards
coordinates ``(x, y, z, t)``.

The only code directly handling point representation is ``crypto.py``.
All other objects are using ``crypto.py`` to do the EC computation.
Point representation is opaque to the other modules.

The opaque point representation can be converted to bytearray
representation suitable for transport (compressed, y-coordinate + sign
flag) using ``crypto.encodepoint()`` and ``crypto.decodepoint()``.

Scalars are represented as integers (no encoding / decoding is needed).
However, we are working in modular ring so for scalar operations such as
addition, division, comparison use the ``crypto.sc_*`` methods.

Trezor-crypto
-------------

Additionally to pure-python crypto backend, there is a production-ready
``trezor-crypto`` backend. I implemented required Monero-related
cryptographic algorithms to the
`trezor-crypto <https://github.com/ph4r05/trezor-crypto>`__ (TCRY). TCRY
implements constant-time curve operations, uses
`libsodium <https://github.com/jedisct1/libsodium>`__ to generate random
values. Borromean Range proof was reimplemented in C for CPU and memory
efficiency.

I created a python binding
`py-trezor-crypto <https://github.com/ph4r05/py-trezor-crypto>`__ which
can be installed from pip. The pip builds
`trezor-crypto <https://github.com/ph4r05/trezor-crypto>`__ library.
Please refer to the readme of the
`py-trezor-crypto <https://github.com/ph4r05/py-trezor-crypto>`__ for
installation details (dependencies).

To install python bindings with agent run:

.. code:: bash

    pip install -U --no-cache 'monero_agent[tcry]'

    # Or laternativelly
    pip install -U --no-cache py_trezor_crypto_ph4 

Dependencies:

-  libsodium
-  pkg-config
-  gcc
-  python-dev

Travis tests with both crypto backends. In order to test with TCRY
install all its dependencies. ``libsodium`` is the only one dependency
for the shared lib. For more info take a look at
``travis-install-libtrezor-crypto.sh``.

Crypto dependency is selected based on the ``EC_BACKEND`` env var. ``0``
is for Python backend, ``1`` for TCRY. Path to the TCRY is specified via
``LIBTREZOR_CRYPTO_PATH`` env var. If the TCRY is not found or could not
be loaded the code fallbacks to python backend. This behaviour can be
changed by setting ``EC_BACKEND_FORCE`` env var to ``1``.

TCRY is also 20 times faster (unit tests).

.. code:: bash

    $> EC_BACKEND_FORCE=1 EC_BACKEND=0  ./venv/bin/python -m unittest monero_glue_test/test_*.py
    ...s................................................................
    ----------------------------------------------------------------------
    Ran 68 tests in 416.823s

    OK

TCRY backend:

.. code:: bash

    $>  EC_BACKEND_FORCE=1 EC_BACKEND=1  ./venv/bin/python -m unittest monero_glue_test/test_*.py
    ....................................................................
    ----------------------------------------------------------------------
    Ran 68 tests in 84.057s

    OK

Testing with Trezor
-------------------

.. code:: bash

    pip3 install -U --no-cache monero-agent py_trezor_crypto_ph4 
    python3 -m unittest trezor_monero_test.test_trezor

    # To test only one transaction:
    TREZOR_TEST_ONLY_TX=1 TREZOR_TEST_NUM_TX=1 python3 -m unittest trezor_monero_test.test_trezor

    # To test with interactive Trezor prompts:
    TREZOR_TEST_INTERACTIVE=1 TREZOR_TEST_ONLY_TX=1 TREZOR_TEST_NUM_TX=1 python3 -m unittest trezor_monero_test.test_trezor

    # Note: if testing with local py files, use trezor_monero_test/test_trezor.py

More on using the repo
----------------------

Please refer to the `PoC.md <PoC.md>`__ for more usage examples.

Memory considerations
~~~~~~~~~~~~~~~~~~~~~

Python uses arbitrary precision integers with a memory overhead. The
following command shows the amount of memory required for certain data
types and sizes:

.. code:: python

    >>> sys.getsizeof(0)
    24
    >>> sys.getsizeof(2**32-1)  # 4B num
    32
    >>> sys.getsizeof(2**64-1)  # 8B num
    36
    >>> sys.getsizeof(2**256-1)  # 32B num
    60
    >>> sys.getsizeof(b'\x00'*32)  # 32B hex
    65
    >>> sys.getsizeof(b'\x00'*64)  # 64B hex
    97

Monero works in EC with 32 B numbers. To store a 32 B number it takes 60
B in integer representation and 65 B in the byte string encoded
representation (some ed25519 libraries and mininero use this
representation). For scalars it is apparently more effective to store
integers naturally, saving both memory and CPU cycles with recoding.

EC point arithmetics can use classic point coordinates ``(x, y)`` or
extended Edwards point coordinates ``(x,y,z,t)``. It takes 64 and 80 B
to store tuple of 2 and 4 elements respectively. It thus take 184 B and
320 B to store an EC point in the natural form compared to the 65 B byte
representation.

Donations
=========

Thanks for your support!

Monero donation address:

::

    88np3NiHwTVDZCNAZWth856ZwriMpp3iRBoAEy4yGWpR17eqqtQYs1RiwcWZexg8Wa8x143p2pu8LWJ7qYutJHjhTQB8gC1

Internal notes
==============

-  Signing client version 3 is not yet implemented. Subaddr index is
   needed for each UTXO.
-  CLSAG algorithm is implemented, but not yet used in the signing
   client

Related projects
================

-  `monero-trezor-doc <https://github.com/ph4r05/monero-trezor-doc>`__ -
   Technical report describing the integration design
-  `monero-serialize <https://github.com/ph4r05/monero-serialize>`__ -
   Monero serialization library
-  `trezor-crypto <https://github.com/ph4r05/trezor-crypto>`__ - Trezor
   crypto library, low-level crypto functions
-  `py-trezor-crypto <https://github.com/ph4r05/py-trezor-crypto>`__ -
   Python binding for Trezor Crypto
-  `py-cryptonight <https://github.com/ph4r05/py-cryptonight>`__ -
   Python binding for Cryptonight hash function
-  `trezor-firmware <https://github.com/ph4r05/trezor-firmware>`__ -
   Trezor firmware monorepository, contains whole firmware, with Monero
   integration
-  `trezor-core <https://github.com/ph4r05/trezor-core>`__ - Deprecated
   Trezor core repo (now included in monorepo)
-  `trezor-crypto <https://github.com/ph4r05/trezor-crypto>`__ -
   Deprecated Trezor crypto repo with low-level crypto functions (now
   included in monorepo)
-  `trezor-common <https://github.com/ph4r05/trezor-common>`__ -
   Deprecated Trezor common repo with protobuf messages and common
   artifacts (now included in monorepo)

.. |Build Status| image:: https://travis-ci.org/ph4r05/monero-agent.svg?branch=master
   :target: https://travis-ci.org/ph4r05/monero-agent