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Scala

Copyright (c) 2021-2023, Haku Labs MTÜ

Copyright (c) 2014-2023, The Monero Project

Portions Copyright (c) 2012-2013 The Cryptonote developers.

Scala is a privacy-focused cryptocurrency project linking distributed technologies to build a globally scalable and mobile-friendly ecosystem. We provide an opaque blockchain, untraceable payments, unlinkable transactions, and blockchain-analysis resistance.

Our vision is to distribute wealth for everyone and every device. We want to be the people’s coin. To achieve this goal, we focus on implementing solutions that are mobile-friendly and energy-efficient. There are about 4 billion mobile devices in the world, and we want to make sure that our ecosystem takes that into account. We also take a lot of time to improve the user experience so that our applications can be used easily by anyone.

Obviously, our goal is also to bring useful utilities and to solve real-world problems, in a way that is economically viable for the project and to sustain our growth. We take advantage of next-gen technologies such as IPFS and custom software to provide the utility of data storage and we use the proven CryptoNote protocol for providing the financial aspects.

Table of Contents

Development resources

Vulnerability response

Please contact us privately at [email protected] to report security issues.

Announcements

All critical announcements regarding the Scala project will be made on the following outlets:

Introduction

Scala is a private, secure, untraceable, decentralised digital currency. You are your bank, you control your funds, and nobody can trace your transfers unless you allow them to do so.

Privacy: scala uses a cryptographically sound system to allow you to send and receive funds without your transactions being easily revealed on the blockchain (the ledger of transactions that everyone has). This ensures that your purchases, receipts, and all transfers remain private by default.

Security: Using the power of a distributed peer-to-peer consensus network, every transaction on the network is cryptographically secured. Individual wallets have a 25-word mnemonic seed that is only displayed once and can be written down to backup the wallet. Wallet files should be encrypted with a strong passphrase to ensure they are useless if ever stolen.

Untraceability: By taking advantage of ring signatures, a special property of a certain type of cryptography, scala is able to ensure that transactions are not only untraceable but have an optional measure of ambiguity that ensures that transactions cannot easily be tied back to an individual user or computer.

Decentralization: The utility of scala depends on its decentralised peer-to-peer consensus network - anyone should be able to run the scala software, validate the integrity of the blockchain, and participate in all aspects of the scala network using consumer-grade commodity hardware. Decentralization of the scala network is maintained by software development that minimizes the costs of running the scala software and inhibits the proliferation of specialized, non-commodity hardware.

About this project

This is the core implementation of scala. It is open source and completely free to use without restrictions, except for those specified in the license agreement below. There are no restrictions on anyone creating an alternative implementation of scala that uses the protocol and network in a compatible manner.

As with many development projects, the repository on GitHub is considered to be the "staging" area for the latest changes. Before changes are merged into that branch on the main repository, they are tested by individual developers in their own branches, submitted as a pull request, and then subsequently tested by contributors who focus on testing and code reviews. That having been said, the repository should be carefully considered before using it in a production environment, unless there is a patch in the repository for a particular show-stopping issue you are experiencing. It is generally a better idea to use a tagged release for stability.

Anyone is welcome to contribute to scala's codebase! If you have a fix or code change, feel free to submit it as a pull request directly to the "master" branch. In cases where the change is relatively small or does not affect other parts of the codebase, it may be merged in immediately by any one of the collaborators. On the other hand, if the change is particularly large or complex, it is expected that it will be discussed at length either well in advance of the pull request being submitted, or even directly on the pull request.

Supporting the project

For information on how scala funds its development, please read this on our wiki.

Core development funding and/or some supporting services are also graciously provided by sponsors:

License

See LICENSE.

Contributing

If you want to help out, see CONTRIBUTING for a set of guidelines.

Scheduled software/network upgrades

scala uses a scheduled software/network upgrade (hard fork) mechanism to implement new features into the scala software and network. This means that users of scala (end users and service providers) should run current versions and upgrade their software when new releases are available. Software upgrades occur when new features are developed and implemented in the codebase. Network upgrades occur in tandem with software upgrades that modify the consensus rules of the scala network. The required software for network upgrades will be available prior to the scheduled network upgrade date. Please check the repository prior to this date for the proper scala software version. Below is the historical schedule and the projected schedule for the next upgrade.

Dates are provided in the format DD-MM-YYYY. The "Minimum" is the software version that follows the new consensus rules. The "Recommended" version may include bug fixes and other new features that do not affect the consensus rules.

Software upgrade block height Date Fork version Minimum scala version Recommended scala version Details
1 1-08-2020 v4.1.0 v4.1.0 v7.9.0 Genesis block
X X v8.0.0 v8.0.0 v8.0.0 Diardi V2, multiple proof of work, new bulletproofs, new reward curve

X's indicate that these details have not been determined as of commit date.

* indicates estimate as of commit date

Release staging schedule and protocol

Approximately three months prior to a scheduled software upgrade, a branch from master will be created with the new release version tag. Pull requests that address bugs should then be made to both master and the new release branch. Pull requests that require extensive review and testing (generally, optimizations and new features) should not be made to the release branch.

Compiling scala from source

Dependencies

The following table summarizes the tools and libraries required to build. A few of the libraries are also included in this repository (marked as "Vendored"). By default, the build uses the library installed on the system and ignores the vendored sources. However, if no library is found installed on the system, then the vendored source will be built and used. The vendored sources are also used for statically-linked builds because distribution packages often include only shared library binaries (.so) but not static library archives (.a).

Dep Min. version Vendored Debian/Ubuntu pkg Arch pkg Void pkg Fedora pkg Optional Purpose
GCC 5 NO build-essential base-devel base-devel gcc NO
CMake 3.5 NO cmake cmake cmake cmake NO
pkg-config any NO pkg-config base-devel base-devel pkgconf NO
Boost 1.58 NO libboost-all-dev boost boost-devel boost-devel NO C++ libraries
OpenSSL basically any NO libssl-dev openssl openssl-devel openssl-devel NO sha256 sum
libzmq 4.2.0 NO libzmq3-dev zeromq zeromq-devel zeromq-devel NO ZeroMQ library
OpenPGM ? NO libpgm-dev libpgm openpgm-devel NO For ZeroMQ
libnorm[2] ? NO libnorm-dev YES For ZeroMQ
libunbound 1.4.16 NO libunbound-dev unbound unbound-devel unbound-devel NO DNS resolver
libsodium ? NO libsodium-dev libsodium libsodium-devel libsodium-devel NO cryptography
libunwind any NO libunwind8-dev libunwind libunwind-devel libunwind-devel YES Stack traces
liblzma any NO liblzma-dev xz liblzma-devel xz-devel YES For libunwind
libreadline 6.3.0 NO libreadline6-dev readline readline-devel readline-devel YES Input editing
expat 1.1 NO libexpat1-dev expat expat-devel expat-devel YES XML parsing
GTest 1.5 YES libgtest-dev[1] gtest gtest-devel gtest-devel YES Test suite
ccache any NO ccache ccache ccache ccache YES Compil. cache
Doxygen any NO doxygen doxygen doxygen doxygen YES Documentation
Graphviz any NO graphviz graphviz graphviz graphviz YES Documentation
lrelease ? NO qttools5-dev-tools qt5-tools qt5-tools qt5-linguist YES Translations
libhidapi ? NO libhidapi-dev hidapi hidapi-devel hidapi-devel YES Hardware wallet
libusb ? NO libusb-1.0-0-dev libusb libusb-devel libusbx-devel YES Hardware wallet
libprotobuf ? NO libprotobuf-dev protobuf protobuf-devel protobuf-devel YES Hardware wallet
protoc ? NO protobuf-compiler protobuf protobuf protobuf-compiler YES Hardware wallet
libudev ? NO libudev-dev systemd eudev-libudev-devel systemd-devel YES Hardware wallet

[1] On Debian/Ubuntu libgtest-dev only includes sources and headers. You must build the library binary manually. This can be done with the following command sudo apt-get install libgtest-dev && cd /usr/src/gtest && sudo cmake . && sudo make then:

  • on Debian: sudo mv libg* /usr/lib/
  • on Ubuntu: sudo mv lib/libg* /usr/lib/

[2] libnorm-dev is needed if your zmq library was built with libnorm, and not needed otherwise

Install all dependencies at once on Debian/Ubuntu:

sudo apt update && sudo apt install build-essential cmake pkg-config libssl-dev libzmq3-dev libunbound-dev libsodium-dev libunwind8-dev liblzma-dev libreadline6-dev libexpat1-dev libpgm-dev qttools5-dev-tools libhidapi-dev libusb-1.0-0-dev libprotobuf-dev protobuf-compiler libudev-dev libboost-chrono-dev libboost-date-time-dev libboost-filesystem-dev libboost-locale-dev libboost-program-options-dev libboost-regex-dev libboost-serialization-dev libboost-system-dev libboost-thread-dev python3 ccache doxygen graphviz

Install all dependencies at once on Arch:

sudo pacman -Syu --needed base-devel cmake boost openssl zeromq libpgm unbound libsodium libunwind xz readline expat gtest python3 ccache doxygen graphviz qt5-tools hidapi libusb protobuf systemd

Install all dependencies at once on Fedora:

sudo dnf install gcc gcc-c++ cmake pkgconf boost-devel openssl-devel zeromq-devel openpgm-devel unbound-devel libsodium-devel libunwind-devel xz-devel readline-devel expat-devel gtest-devel ccache doxygen graphviz qt5-linguist hidapi-devel libusbx-devel protobuf-devel protobuf-compiler systemd-devel

Install all dependencies at once on openSUSE:

sudo zypper ref && sudo zypper in cppzmq-devel libboost_chrono-devel libboost_date_time-devel libboost_filesystem-devel libboost_locale-devel libboost_program_options-devel libboost_regex-devel libboost_serialization-devel libboost_system-devel libboost_thread-devel libexpat-devel libminiupnpc-devel libsodium-devel libunwind-devel unbound-devel cmake doxygen ccache fdupes gcc-c++ libevent-devel libopenssl-devel pkgconf-pkg-config readline-devel xz-devel libqt5-qttools-devel patterns-devel-C-C++-devel_C_C++

Install all dependencies at once on macOS with the provided Brewfile:

brew update && brew bundle --file=contrib/brew/Brewfile

FreeBSD 12.1 one-liner required to build dependencies:

pkg install git gmake cmake pkgconf boost-libs libzmq4 libsodium unbound

Cloning the repository

Clone recursively to pull-in needed submodule(s):

git clone --recursive https://github.com/scala-network/scala

If you already have a repo cloned, initialize and update:

cd scala && git submodule init && git submodule update

Note: If there are submodule differences between branches, you may need to use git submodule sync && git submodule update after changing branches to build successfully.

Build instructions

scala uses the CMake build system and a top-level Makefile that invokes cmake commands as needed.

On Linux and macOS

  • Install the dependencies

  • Change to the root of the source code directory, change to the most recent release branch, and build:

    cd scala
make

    Optional: If your machine has several cores and enough memory, enable parallel build by running make -j<number of threads> instead of make. For this to be worthwhile, the machine should have one core and about 2GB of RAM available per thread.

    Note: The instructions above will compile the most stable release of the scala software. If you would like to use and test the most recent software, use git checkout master. The master branch may contain updates that are both unstable and incompatible with release software, though testing is always encouraged.

  • The resulting executables can be found in build/release/bin

  • Add PATH="$PATH:$HOME/scala/build/release/bin" to .profile

  • Run scala with scalad --detach

  • Optional: build and run the test suite to verify the binaries:

    make release-test

    NOTE: core_tests test may take a few hours to complete.

  • Optional: to build binaries suitable for debugging:

    make debug

  • Optional: to build statically-linked binaries:

    make release-static

Dependencies need to be built with -fPIC. Static libraries usually aren't, so you may have to build them yourself with -fPIC. Refer to their documentation for how to build them.

  • Optional: build documentation in doc/html (omit HAVE_DOT=YES if graphviz is not installed):

    HAVE_DOT=YES doxygen Doxyfile

  • Optional: use ccache not to rebuild translation units, that haven't really changed. scala's CMakeLists.txt file automatically handles it

    sudo apt install ccache

On the Raspberry Pi

Tested on a Raspberry Pi Zero with a clean install of minimal Raspbian Stretch (2017-09-07 or later) from https://www.raspberrypi.org/downloads/raspbian/. If you are using Raspian Jessie, please see note in the following section.

  • apt-get update && apt-get upgrade to install all of the latest software

  • Install the dependencies for scala from the 'Debian' column in the table above.

  • Increase the system swap size:

    sudo /etc/init.d/dphys-swapfile stop  
sudo nano /etc/dphys-swapfile  
CONF_SWAPSIZE=2048
sudo /etc/init.d/dphys-swapfile start

  • If using an external hard disk without an external power supply, ensure it gets enough power to avoid hardware issues when syncing, by adding the line "max_usb_current=1" to /boot/config.txt

  • Clone scala and checkout the most recent release version:

    git clone https://github.com/scala-network/scala.git
cd scala
git checkout v0.18.1.2

  • Build:

    USE_SINGLE_BUILDDIR=1 make release

  • Wait 4-6 hours

  • The resulting executables can be found in build/release/bin

  • Add export PATH="$PATH:$HOME/scala/build/release/bin" to $HOME/.profile

  • Run source $HOME/.profile

  • Run scala with scalad --detach

  • You may wish to reduce the size of the swap file after the build has finished, and delete the boost directory from your home directory

Note for Raspbian Jessie users:

If you are using the older Raspbian Jessie image, compiling scala is a bit more complicated. The version of Boost available in the Debian Jessie repositories is too old to use with scala, and thus you must compile a newer version yourself. The following explains the extra steps and has been tested on a Raspberry Pi 2 with a clean install of minimal Raspbian Jessie.

  • As before, apt-get update && apt-get upgrade to install all of the latest software, and increase the system swap size

    sudo /etc/init.d/dphys-swapfile stop
sudo nano /etc/dphys-swapfile
CONF_SWAPSIZE=2048
sudo /etc/init.d/dphys-swapfile start

  • Then, install the dependencies for scala except for libunwind and libboost-all-dev

  • Install the latest version of boost (this may first require invoking apt-get remove --purge libboost*-dev to remove a previous version if you're not using a clean install):

    cd
wget https://sourceforge.net/projects/boost/files/boost/1.72.0/boost_1_72_0.tar.bz2
tar xvfo boost_1_72_0.tar.bz2
cd boost_1_72_0
./bootstrap.sh
sudo ./b2

  • Wait ~8 hours

    sudo ./bjam cxxflags=-fPIC cflags=-fPIC -a install

  • Wait ~4 hours

  • From here, follow the general Raspberry Pi instructions from the "Clone scala and checkout most recent release version" step.

On Windows:

Binaries for Windows are built on Windows using the MinGW toolchain within MSYS2 environment. The MSYS2 environment emulates a POSIX system. The toolchain runs within the environment and cross-compiles binaries that can run outside of the environment as a regular Windows application.

Preparing the build environment

  • Download and install the MSYS2 installer, either the 64-bit or the 32-bit package, depending on your system.

  • Open the MSYS shell via the MSYS2 Shell shortcut

  • Update packages using pacman:

    pacman -Syu

  • Exit the MSYS shell using Alt+F4

  • Edit the properties for the MSYS2 Shell shortcut changing "msys2_shell.bat" to "msys2_shell.cmd -mingw64" for 64-bit builds or "msys2_shell.cmd -mingw32" for 32-bit builds

  • Restart MSYS shell via modified shortcut and update packages again using pacman:

    pacman -Syu

  • Install dependencies:

    To build for 64-bit Windows:

    pacman -S mingw-w64-x86_64-toolchain make mingw-w64-x86_64-cmake mingw-w64-x86_64-boost mingw-w64-x86_64-openssl mingw-w64-x86_64-zeromq mingw-w64-x86_64-libsodium mingw-w64-x86_64-hidapi mingw-w64-x86_64-unbound

    To build for 32-bit Windows:

    pacman -S mingw-w64-i686-toolchain make mingw-w64-i686-cmake mingw-w64-i686-boost mingw-w64-i686-openssl mingw-w64-i686-zeromq mingw-w64-i686-libsodium mingw-w64-i686-hidapi mingw-w64-i686-unbound

  • Open the MingW shell via MinGW-w64-Win64 Shell shortcut on 64-bit Windows or MinGW-w64-Win64 Shell shortcut on 32-bit Windows. Note that if you are running 64-bit Windows, you will have both 64-bit and 32-bit MinGW shells.

Cloning

  • To git clone, run:

    git clone --recursive https://github.com/scala-network/scala.git

Building

  • Change to the cloned directory, run:

    cd scala

  • If you would like a specific version/tag, do a git checkout for that version. eg. 'v0.18.1.2'. If you don't care about the version and just want binaries from master, skip this step:

    git checkout v0.18.1.2

  • If you are on a 64-bit system, run:

    make release-static-win64

  • If you are on a 32-bit system, run:

    make release-static-win32

  • The resulting executables can be found in build/release/bin

  • Optional: to build Windows binaries suitable for debugging on a 64-bit system, run:

    make debug-static-win64

  • Optional: to build Windows binaries suitable for debugging on a 32-bit system, run:

    make debug-static-win32

  • The resulting executables can be found in build/debug/bin

On FreeBSD:

The project can be built from scratch by following instructions for Linux above(but use gmake instead of make). If you are running scala in a jail, you need to add sysvsem="new" to your jail configuration, otherwise lmdb will throw the error message: Failed to open lmdb environment: Function not implemented.

scala is also available as a port or package as scala-cli.

On OpenBSD:

You will need to add a few packages to your system. pkg_add cmake gmake zeromq libiconv boost libunbound.

The doxygen and graphviz packages are optional and require the xbase set. Running the test suite also requires py3-requests package.

Build scala: gmake

Note: you may encounter the following error when compiling the latest version of scala as a normal user:

LLVM ERROR: out of memory
c++: error: unable to execute command: Abort trap (core dumped)

Then you need to increase the data ulimit size to 2GB and try again: ulimit -d 2000000

On NetBSD:

Check that the dependencies are present: pkg_info -c libexecinfo boost-headers boost-libs protobuf readline libusb1 zeromq git-base pkgconf gmake cmake | more, and install any that are reported missing, using pkg_add or from your pkgsrc tree. Readline is optional but worth having.

Third-party dependencies are usually under /usr/pkg/, but if you have a custom setup, adjust the "/usr/pkg" (below) accordingly.

Clone the scala repository recursively and checkout the most recent release as described above. Then build scala: gmake BOOST_ROOT=/usr/pkg LDFLAGS="-Wl,-R/usr/pkg/lib" release. The resulting executables can be found in build/NetBSD/[Release version]/Release/bin/.

On Solaris:

The default Solaris linker can't be used, you have to install GNU ld, then run cmake manually with the path to your copy of GNU ld:

mkdir -p build/release
cd build/release
cmake -DCMAKE_LINKER=/path/to/ld -D CMAKE_BUILD_TYPE=Release ../..
cd ../..

Then you can run make as usual.

Building portable statically linked binaries

By default, in either dynamically or statically linked builds, binaries target the specific host processor on which the build happens and are not portable to other processors. Portable binaries can be built using the following targets:

  • make release-static-linux-x86_64 builds binaries on Linux on x86_64 portable across POSIX systems on x86_64 processors
  • make release-static-linux-i686 builds binaries on Linux on x86_64 or i686 portable across POSIX systems on i686 processors
  • make release-static-linux-armv8 builds binaries on Linux portable across POSIX systems on armv8 processors
  • make release-static-linux-armv7 builds binaries on Linux portable across POSIX systems on armv7 processors
  • make release-static-linux-armv6 builds binaries on Linux portable across POSIX systems on armv6 processors
  • make release-static-win64 builds binaries on 64-bit Windows portable across 64-bit Windows systems
  • make release-static-win32 builds binaries on 64-bit or 32-bit Windows portable across 32-bit Windows systems

Cross Compiling

You can also cross-compile static binaries on Linux for Windows and macOS with the depends system.

  • make depends target=x86_64-linux-gnu for 64-bit linux binaries.
  • make depends target=x86_64-w64-mingw32 for 64-bit windows binaries.
    • Requires: python3 g++-mingw-w64-x86-64 wine1.6 bc
    • You also need to run:
      update-alternatives --set x86_64-w64-mingw32-g++ x86_64-w64-mingw32-g++-posix && update-alternatives --set x86_64-w64-mingw32-gcc x86_64-w64-mingw32-gcc-posix
  • make depends target=x86_64-apple-darwin11 for macOS binaries.
    • Requires: cmake imagemagick libcap-dev librsvg2-bin libz-dev libbz2-dev libtiff-tools python-dev
  • make depends target=i686-linux-gnu for 32-bit linux binaries.
    • Requires: g++-multilib bc
  • make depends target=i686-w64-mingw32 for 32-bit windows binaries.
    • Requires: python3 g++-mingw-w64-i686
  • make depends target=arm-linux-gnueabihf for armv7 binaries.
    • Requires: g++-arm-linux-gnueabihf
  • make depends target=aarch64-linux-gnu for armv8 binaries.
    • Requires: g++-aarch64-linux-gnu
  • make depends target=riscv64-linux-gnu for RISC V 64 bit binaries.
    • Requires: g++-riscv64-linux-gnu
  • make depends target=x86_64-unknown-freebsd for freebsd binaries.
    • Requires: clang-8
  • make depends target=arm-linux-android for 32bit android binaries
  • make depends target=aarch64-linux-android for 64bit android binaries

The required packages are the names for each toolchain on apt. Depending on your distro, they may have different names. The depends system has been tested on Ubuntu 18.04 and 20.04.

Using depends might also be easier to compile scala on Windows than using MSYS. Activate Windows Subsystem for Linux (WSL) with a distro (for example Ubuntu), install the apt build-essentials and follow the depends steps as depicted above.

The produced binaries still link libc dynamically. If the binary is compiled on a current distribution, it might not run on an older distribution with an older installation of libc. Passing -DBACKCOMPAT=ON to cmake will make sure that the binary will run on systems having at least libc version 2.17.

Gitian builds

See contrib/gitian/README.md.

Installing scala from a package

DISCLAIMER: These packages are not part of this repository or maintained by this project's contributors, and as such, do not go through the same review process to ensure their trustworthiness and security.

Packages are available for

More info and versions in the Debian package tracker.

  • Arch Linux (via Community packages):

    sudo pacman -S scala

  • Void Linux:

    xbps-install -S scala

  • GuixSD

    guix package -i scala

  • Gentoo scala overlay

    emerge --noreplace eselect-repository
eselect repository enable scala
emaint sync -r scala
echo '*/*::scala ~amd64' >> /etc/portage/package.accept_keywords
emerge net-p2p/scala

  • macOS (homebrew)

    brew install scala

  • Docker

    # Build using all available cores
docker build -t scala .

# or build using a specific number of cores (reduce RAM requirement)
docker build --build-arg NPROC=1 -t scala .

# either run in foreground
docker run -it -v /scala/chain:/home/scala/.bitscala -v /scala/wallet:/wallet -p 18080:18080 scala

# or in background
docker run -it -d -v /scala/chain:/home/scala/.bitscala -v /scala/wallet:/wallet -p 18080:18080 scala

  • The build needs 3 GB space.

  • Wait one hour or more

Packaging for your favorite distribution would be a welcome contribution!

Running scalad

The build places the binary in bin/ sub-directory within the build directory from which cmake was invoked (repository root by default). To run in the foreground:

./bin/scalad

To list all available options, run ./bin/scalad --help. Options can be specified either on the command line or in a configuration file passed by the --config-file argument. To specify an option in the configuration file, add a line with the syntax argumentname=value, where argumentname is the name of the argument without the leading dashes, for example, log-level=1.

To run in background:

./bin/scalad --log-file scalad.log --detach

To run as a systemd service, copy scalad.service to /etc/systemd/system/ and scalad.conf to /etc/. The example service assumes that the user scala exists and its home is the data directory specified in the example config.

If you're on Mac, you may need to add the --max-concurrency 1 option to scala-wallet-cli, and possibly scalad, if you get crashes refreshing.

Internationalization

See README.i18n.md.

Using Tor

There is a new, still experimental, integration with Tor. The feature allows connecting over IPv4 and Tor simultaneously - IPv4 is used for relaying blocks and relaying transactions received by peers whereas Tor is used solely for relaying transactions received over local RPC. This provides privacy and better protection against surrounding node (sybil) attacks.

While scala isn't made to integrate with Tor, it can be used wrapped with torsocks, by setting the following configuration parameters and environment variables:

  • --p2p-bind-ip 127.0.0.1 on the command line or p2p-bind-ip=127.0.0.1 in scalad.conf to disable listening for connections on external interfaces.
  • --no-igd on the command line or no-igd=1 in scalad.conf to disable IGD (UPnP port forwarding negotiation), which is pointless with Tor.
  • DNS_PUBLIC=tcp or DNS_PUBLIC=tcp://x.x.x.x where x.x.x.x is the IP of the desired DNS server, for DNS requests to go over TCP, so that they are routed through Tor. When IP is not specified, scalad uses the default list of servers defined in src/common/dns_utils.cpp.
  • TORSOCKS_ALLOW_INBOUND=1 to tell torsocks to allow scalad to bind to interfaces to accept connections from the wallet. On some Linux systems, torsocks allows binding to localhost by default, so setting this variable is only necessary to allow binding to local LAN/VPN interfaces to allow wallets to connect from remote hosts. On other systems, it may be needed for local wallets as well.
  • Do NOT pass --detach when running through torsocks with systemd, (see utils/systemd/scalad.service for details).
  • If you use the wallet with a Tor daemon via the loopback IP (eg, 127.0.0.1:9050), then use --untrusted-daemon unless it is your own hidden service.

Example command line to start scalad through Tor:

DNS_PUBLIC=tcp torsocks scalad --p2p-bind-ip 127.0.0.1 --no-igd

A helper script is in contrib/tor/scala-over-tor.sh. It assumes Tor is installed already, and runs Tor and scala with the right configuration.

Using Tor on Tails

TAILS ships with a very restrictive set of firewall rules. Therefore, you need to add a rule to allow this connection too, in addition to telling torsocks to allow inbound connections. Full example:

sudo iptables -I OUTPUT 2 -p tcp -d 127.0.0.1 -m tcp --dport 18081 -j ACCEPT
DNS_PUBLIC=tcp torsocks ./scalad --p2p-bind-ip 127.0.0.1 --no-igd --rpc-bind-ip 127.0.0.1 \
    --data-dir /home/amnesia/Persistent/your/directory/to/the/blockchain

Pruning

As of April 2022, the full scala blockchain file is about 130 GB. One can store a pruned blockchain, which is about 45 GB. A pruned blockchain can only serve part of the historical chain data to other peers, but is otherwise identical in functionality to the full blockchain. To use a pruned blockchain, it is best to start the initial sync with --prune-blockchain. However, it is also possible to prune an existing blockchain using the scala-blockchain-prune tool or using the --prune-blockchain scalad option with an existing chain. If an existing chain exists, pruning will temporarily require disk space to store both the full and pruned blockchains.

Debugging

This section contains general instructions for debugging failed installs or problems encountered with scala. First, ensure you are running the latest version built from the GitHub repo.

Obtaining stack traces and core dumps on Unix systems

We generally use the tool gdb (GNU debugger) to provide stack trace functionality, and ulimit to provide core dumps in builds which crash or segfault.

  • To use gdb in order to obtain a stack trace for a build that has stalled:

Run the build.

Once it stalls, enter the following command:

gdb /path/to/scalad `pidof scalad`

Type thread apply all bt within gdb in order to obtain the stack trace

  • If however the core dumps or segfaults:

Enter ulimit -c unlimited on the command line to enable unlimited filesizes for core dumps

Enter echo core | sudo tee /proc/sys/kernel/core_pattern to stop cores from being hijacked by other tools

Run the build.

When it terminates with an output along the lines of "Segmentation fault (core dumped)", there should be a core dump file in the same directory as scalad. It may be named just core, or core.xxxx with numbers appended.

You can now analyse this core dump with gdb as follows:

gdb /path/to/scalad /path/to/dumpfile`

Print the stack trace with bt

  • If a program crashed and cores are managed by systemd, the following can also get a stack trace for that crash:
coredumpctl -1 gdb

To run scala within gdb:

Type gdb /path/to/scalad

Pass command-line options with --args followed by the relevant arguments

Type run to run scalad

Analysing memory corruption

There are two tools available:

ASAN

Configure scala with the -D SANITIZE=ON cmake flag, eg:

cd build/debug && cmake -D SANITIZE=ON -D CMAKE_BUILD_TYPE=Debug ../..

You can then run the scala tools normally. Performance will typically halve.

valgrind

Install valgrind and run as valgrind /path/to/scalad. It will be very slow.

LMDB

Instructions for debugging suspected blockchain corruption as per @HYC

There is an mdb_stat command in the LMDB source that can print statistics about the database but it's not routinely built. This can be built with the following command:

cd ~/scala/external/db_drivers/liblmdb && make

The output of mdb_stat -ea <path to blockchain dir> will indicate inconsistencies in the blocks, block_heights and block_info table.

The output of mdb_dump -s blocks <path to blockchain dir> and mdb_dump -s block_info <path to blockchain dir> is useful for indicating whether blocks and block_info contain the same keys.

These records are dumped as hex data, where the first line is the key and the second line is the data.

Known Issues

Protocols

Socket-based

Because of the nature of the socket-based protocols that drive scala, certain protocol weaknesses are somewhat unavoidable at this time. While these weaknesses can theoretically be fully mitigated, the effort required (the means) may not justify the ends. As such, please consider taking the following precautions if you are a scala node operator:

  • Run scalad on a "secured" machine. If operational security is not your forte, at a very minimum, have a dedicated a computer running scalad and do not browse the web, use email clients, or use any other potentially harmful apps on your scalad machine. Do not click links or load URL/MUA content on the same machine. Doing so may potentially exploit weaknesses in commands which accept "localhost" and "127.0.0.1".
  • If you plan on hosting a public "remote" node, start scalad with --restricted-rpc. This is a must.

Blockchain-based

Certain blockchain "features" can be considered "bugs" if misused correctly. Consequently, please consider the following:

  • When receiving scala, be aware that it may be locked for an arbitrary time if the sender elected to, preventing you from spending that scala until the lock time expires. You may want to hold off acting upon such a transaction until the unlock time lapses. To get a sense of that time, you can consider the remaining blocktime until unlock as seen in the show_transfers command.

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Scala v8.0.3 Latest
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