7e2d9c48d1
This fixes three bugs:
- too large targets: the fixme in target_to_bits, which meant that we could
not handle targets where the first bit was non-zero. This however cannot
happen due to these being over MAX_TARGET. (difficulty 1)
- too small targets: in bits_to_target, very small targets were not handled well:
```
>>> Blockchain.bits_to_target(0x03008000)
32768
```
We could not process headers with targets smaller than the above value.
(note that these small targets would only occur at astronomically high mining difficulty)
- non-canonically encoded targets:
we would not accept headers that had targets encoded in compact form (nBits) in a non-canonical way.
I think this bug could actually be triggered by mining such a header.
E.g. consider the target "1167130406913723784571467005534932607254396928"
```
Blockchain.target_to_bits(1167130406913723784571467005534932607254396928).to_bytes(4, "big").hex()
'13345600'
```
Bitcoin Core when used to e.g. mine a block would encode this target as 0x13345600 in compact form.
However, AFAICT, when validating Bitcoin Core would equally accept 0x14003456 which decodes to the
same target. We were however rejecting such non-canonical compact nBits.
```
>>> from electrum.blockchain import Blockchain
>>> Blockchain.bits_to_target(0x14003456)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/user/wspace/electrum/electrum/blockchain.py", line 548, in bits_to_target
raise Exception("Second part of bits should be in [0x8000, 0x7fffff]")
Exception: Second part of bits should be in [0x8000, 0x7fffff]
>>> Blockchain.bits_to_target(0x13345600)
1167130406913723784571467005534932607254396928
```
Electrum - Lightweight Bitcoin client
=====================================
::
Licence: MIT Licence
Author: Thomas Voegtlin
Language: Python (>= 3.6)
Homepage: https://electrum.org/
.. image:: https://api.cirrus-ci.com/github/spesmilo/electrum.svg?branch=master
:target: https://cirrus-ci.com/github/spesmilo/electrum
:alt: Build Status
.. image:: https://coveralls.io/repos/github/spesmilo/electrum/badge.svg?branch=master
:target: https://coveralls.io/github/spesmilo/electrum?branch=master
:alt: Test coverage statistics
.. image:: https://d322cqt584bo4o.cloudfront.net/electrum/localized.svg
:target: https://crowdin.com/project/electrum
:alt: Help translate Electrum online
Getting started
===============
(*If you've come here looking to simply run Electrum,* `you may download it here`_.)
.. _you may download it here: https://electrum.org/#download
Electrum itself is pure Python, and so are most of the required dependencies,
but not everything. The following sections describe how to run from source, but here
is a TL;DR::
sudo apt-get install libsecp256k1-0
python3 -m pip install --user .[gui,crypto]
Not pure-python dependencies
----------------------------
If you want to use the Qt interface, install the Qt dependencies::
sudo apt-get install python3-pyqt5
For elliptic curve operations, `libsecp256k1`_ is a required dependency::
sudo apt-get install libsecp256k1-0
Alternatively, when running from a cloned repository, a script is provided to build
libsecp256k1 yourself::
sudo apt-get install automake libtool
./contrib/make_libsecp256k1.sh
Due to the need for fast symmetric ciphers, `cryptography`_ is required.
Install from your package manager (or from pip)::
sudo apt-get install python3-cryptography
If you would like hardware wallet support, see `this`_.
.. _libsecp256k1: https://github.com/bitcoin-core/secp256k1
.. _pycryptodomex: https://github.com/Legrandin/pycryptodome
.. _cryptography: https://github.com/pyca/cryptography
.. _this: https://github.com/spesmilo/electrum-docs/blob/master/hardware-linux.rst
Running from tar.gz
-------------------
If you downloaded the official package (tar.gz), you can run
Electrum from its root directory without installing it on your
system; all the pure python dependencies are included in the 'packages'
directory. To run Electrum from its root directory, just do::
./run_electrum
You can also install Electrum on your system, by running this command::
sudo apt-get install python3-setuptools python3-pip
python3 -m pip install --user .
This will download and install the Python dependencies used by
Electrum instead of using the 'packages' directory.
It will also place an executable named :code:`electrum` in :code:`~/.local/bin`,
so make sure that is on your :code:`PATH` variable.
Development version (git clone)
-------------------------------
Check out the code from GitHub::
git clone git://github.com/spesmilo/electrum.git
cd electrum
git submodule update --init
Run install (this should install dependencies)::
python3 -m pip install --user -e .
Create translations (optional)::
sudo apt-get install python-requests gettext
./contrib/pull_locale
Finally, to start Electrum::
./run_electrum
Creating Binaries
=================
Linux (tarball)
---------------
See :code:`contrib/build-linux/sdist/README.md`.
Linux (AppImage)
----------------
See :code:`contrib/build-linux/appimage/README.md`.
Mac OS X / macOS
----------------
See :code:`contrib/osx/README.md`.
Windows
-------
See :code:`contrib/build-wine/README.md`.
Android
-------
See :code:`contrib/android/Readme.md`.
Contributing
============
Any help testing the software, reporting or fixing bugs, reviewing pull requests
and recent changes, writing tests, or helping with outstanding issues is very welcome.
Implementing new features, or improving/refactoring the codebase, is of course
also welcome, but to avoid wasted effort, especially for larger changes,
we encourage discussing these on the issue tracker or IRC first.
Besides `GitHub`_, most communication about Electrum development happens on IRC, in the
:code:`#electrum` channel on Libera Chat. The easiest way to participate on IRC is
with the web client, `web.libera.chat`_.
.. _web.libera.chat: https://web.libera.chat/#electrum
.. _GitHub: https://github.com/spesmilo/electrum