Zside

What is Zside?

Zside is a Bitcoin sidechain based off of Zcash.

is an implementation of the "Zerocash" protocol. Based on Bitcoin's code, Zcash intends to offer a far higher standard of privacy through a sophisticated zero-knowledge proving scheme that preserves confidentiality of transaction metadata. More technical details are available in our Protocol Specification.

This software is the Zside client.

Build from Source (Sidechain Version)

Non-Nix (Ubuntu)

First, install the Zcash build dependencies. These can be found on the official Zcash docs. Only install the dependencies listed in the apt-get block, and skip the rest of the instructions.

Once you have installed the build dependencies:

# build all dependencies
$ make -C ./depends/

$ ./autogen.sh
$ HOST=$(./depends/config.guess)

# Use the previously compiled dependencies instead of system libraries
$ export CONFIG_SITE="$PWD/depends/$HOST/share/config.site"  

# Configure the build
$ ./configure --disable-tests --disable-bench --disable-hardening --enable-online-rust

# Build the Rust C++ bindings + bridge
$ make -C src cargo-build-lib

# Find the location of the newly compiled Rust C++ bridge library
$ BRIDGE_LOCATION=$(dirname $(./contrib/devtools/find-libcxxbridge.sh))

# Instruct the linker to include the Rust C++ bridge library
$ export LDFLAGS="-L$BRIDGE_LOCATION -lcxxbridge1" 

# Reconfigure the build, taking our freshly compiled Rust C++ bridge into account.
$ ./configure --disable-tests --disable-bench --disable-hardening --enable-online-rust

# Run the actual build
$ make -j # omit the -j if running into memory issues

The observant reader will note that this requires a bit of back and forth, which might seem odd. Two calls to ./configure, what's this??

The issue boils down to the following:

1. We're building a C++ library based on generated C++ code from Rust sources (in the make -C src cargo-build-lib step)
2. This needs to have the same C++ toolchain configuration as the rest of the build
3. The output of this (libcxxbridge1.a) must be included in the linker flags (LDFLAGS) for the build to succeed
4. However, the Rust libraries have to be in place before we invoke ./configure... This leads to an awkward chicken-or-egg situation.
5. The solution (it might be a strange one, perhaps there's better options) is to run ./configure twice, and doing the Rust build step in-between.

macOS

Building on macOS is not as well supported as on Linux. The upstream Zcash repo doesn't fully support macOS, and our support is monkey-patched in by a guy who doesn't fully know what he's doing.

Building upstream Zcash is not supported at all on ARM chips. However, macOS has very good support for running x86_64 binaries, through Rosetta. We therefore build for x86_64 chips, and use these binaries to run on both newer and older machine.

Install build dependencies:

$ brew install git pkgconfig automake autoconf libtool coreutils

The rest of the instructions are the same as for building for Linux, except that two environment variables need to be set:

export BUILD=x86_64-apple-darwin23.0.0
export HOST=$BUILD

These variables have been attempted to be set through the build system instead, without success. If someone more skilled at the build system than the previous author strolls along, please take a look.

Cross-compiling from Linux to Windows

Building binaries for Windows must happen through cross-compiling from a Linux machine. This requires a rather specific set of packages on the host machine, so the easiest way is to do this through a Docker container. We use the electriccoinco/zcashd-build-ubuntu-jammy image, provided by the upstream Zcash devs.

# from the root of this repo
$ docker run -ti -v $PWD:/zside --workdir /zside electriccoinco/zcashd-build-ubuntu-jammy bash

$ HOST=x86_64-w64-mingw32 make -C depends V=1 -j8
$ export CONFIG_SITE=$PWD/depends/x86_64-w64-mingw32/share/config.site
$ ./autogen.sh
$ ./configure --disable-tests --disable-bench --disable-hardening --enable-online-rust
$ make -C src cargo-build-lib
$ BRIDGE_LOCATION=$(dirname $(./contrib/devtools/find-libcxxbridge.sh))
$ export LDFLAGS="-L$BRIDGE_LOCATION -lcxxbridge1" 
$ ./configure --disable-tests --disable-bench --disable-hardening --enable-online-rust
$ make -j8

# final result is in ./src/zsided.exe

Nix - currently not working

To install all dependencies and build zcash-sidechain on ubuntu (22.04) run:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install git curl
# install nix package manager
sh <(curl -L https://nixos.org/nix/install) --daemon
# now follow the instructions and then close and open the terminal (to get nix initialized)
git clone [email protected]:nchashch/zcash-sidechain.git
cd zcash-sidechain
nix-shell # this will install all build tools and dependencies
./autogen.sh
./configure $configureFlags
make -j8 # or number of cores you want to use

General build notes

• Binary sizes. The zsided and zside-cli binaries are large. Linux binaries are around 150MB, and Windows binaries are over 200MB! They can be reduced by setting CFLAGS and CXXFLAGS to -g0. This disables debug information, and more than halves binary sizes.

Regtest Demo Script

A script for: activating this sidechain (on drivechain), mining blocks, depositing and withdrawing coins, generating t/z addresses and using them, is available here.

License

For license information see the file COPYING.