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Contents

• Contents
• About
• Beta Releases
• Getting Started
• Known Issues
• Future Work
• Documentation
• Security
• License

About

Zebra is the Zcash Foundation's independent, consensus-compatible implementation of a Zcash node, currently under development. It can be used to join the Zcash peer-to-peer network, which helps keeping Zcash working by validating and broadcasting transactions, and maintaining the Zcash blockchain state in a distributed manner. Please join us on Discord if you'd like to find out more or get involved!

Zcash is a cryptocurrency designed to preserve the user's privacy. Like most cryptocurrencies, it works by a collection of software nodes run by members of the Zcash community or any other interested parties. The nodes talk to each other in peer-to-peer fashion in order to maintain the state of the Zcash blockchain. They also communicate with miners who create new blocks. When a Zcash user sends Zcash, their wallet broadcasts transactions to these nodes which will eventually reach miners, and the mined transaction will then go through Zcash nodes until they reach the recipient's wallet which will report the received Zcash to the recipient.

The original Zcash node is named zcashd and is developed by the Electric Coin Company as a fork of the original Bitcoin node. Zebra, on the other hand, is an independent Zcash node implementation developed from scratch. Since they implement the same protocol, zcashd and Zebra nodes can communicate with each other and maintain the Zcash network interoperably.

If you just want to send and receive Zcash then you don't need to use Zebra directly. You can download a Zcash wallet application which will handle that for you. (Eventually, Zebra can be used by wallets to implement their functionality.) You would want to run Zebra if you want to contribute to the Zcash network: the more nodes are run, the more reliable the network will be in terms of speed and resistance to denial of service attacks, for example.

These are some of the advantages or benefits of Zebra:

• Better performance: since it was implemented from scratch in an async, parallelized way, Zebra is currently faster than zcashd.
• Better security: since it is developed in a memory-safe language (Rust), Zebra is less likely to be affected by memory-safety and correctness security bugs that could compromise the environment where it is run.
• Better governance: with a new node deployment, there will be more developers who can implement different features for the Zcash network.
• Dev accessibility: supports more developers, which gives new developers options for contributing to Zcash protocol development.
• Runtime safety: with an independent implementation, the detection of consensus bugs can happen quicker, reducing the risk of consensus splits.
• Spec safety: with several node implementations, it is much easier to notice bugs and ambiguity in protocol specification.
• User options: different nodes present different features and tradeoffs for users to decide on their preferred options.
• Additional contexts: wider target deployments for people to use a consensus node in more contexts e.g. mobile, wasm, etc.

Beta Releases

Every few weeks, we release a new Zebra beta release.

Zebra's network stack is interoperable with zcashd, and Zebra implements all the features required to reach Zcash network consensus.

The goals of the beta release series are for Zebra to act as a fully validating Zcash node, for all active consensus rules as of NU5 activation.

Currently, Zebra validates all of the Zcash consensus rules for the NU5 network upgrade. (As of the second NU5 activation on testnet.)

But it may not validate any:

• Undocumented rules derived from Bitcoin
• Undocumented network protocol requirements

Getting Started

Building zebrad requires Rust, libclang, and a C++ compiler.

Build and Run Instructions

zebrad is still under development, so there is no supported packaging or install mechanism. To run zebrad, follow the instructions to compile zebrad for your platform:

1. Install cargo and rustc.
2. Install Zebra's build dependencies:
   • libclang: the libclang, libclang-dev, llvm, or llvm-dev packages, depending on your package manager
   • clang or another C++ compiler: g++, Xcode, or MSVC
3. Run cargo install --locked --git https://github.com/ZcashFoundation/zebra --tag v1.0.0-beta.8 zebrad
4. Run zebrad start (see Running Zebra for more information)

If you're interested in testing out zebrad please feel free, but keep in mind that there is a lot of key functionality still missing.

For more detailed instructions, refer to the documentation.

System Requirements

The recommended requirements for compiling and running zebrad are:

• 4+ CPU cores
• 16+ GB RAM
• 50GB+ available disk space for building binaries and storing finalized state
• 100+ Mbps network connections

We continuously test that our builds and tests pass on:

The latest GitHub Runners for:

• macOS
• Ubuntu

Docker:

• Debian Bullseye

Zebra's tests can take over an hour, depending on your machine. We're working on making them faster.

zebrad might build and run fine on smaller and slower systems - we haven't tested its exact limits yet.

For more detailed requirements, refer to the documentation.

Memory Troubleshooting

If Zebra's build runs out of RAM, try setting: export CARGO_BUILD_JOBS=2

If Zebra's tests timeout or run out of RAM, try running: cargo test -- --test-threads=2

(cargo uses all the processor cores on your machine by default.)

macOS Test Troubleshooting

Some of Zebra's tests deliberately cause errors that make Zebra panic. macOS records these panics as crash reports.

If you are seeing "Crash Reporter" dialogs during Zebra tests, you can disable them using this Terminal.app command:

defaults write com.apple.CrashReporter DialogType none

Network Ports and Data Usage

By default, Zebra uses the following inbound TCP listener ports:

• 8233 on Mainnet
• 18233 on Testnet

Zebra needs some peers which have a round-trip latency of 2 seconds or less. If this is a problem for you, please open a ticket.

zebrad's typical mainnet network usage is:

• Initial sync: 30 GB download
• Ongoing updates: 10-100 MB upload and download per day, depending on peer requests

Zebra also performs an initial sync every time its internal database version changes.

For more detailed information, refer to the documentation.

Network Troubleshooting

Some of Zebra's tests download Zcash blocks, so they might be unreliable depending on your network connection. You can set ZEBRA_SKIP_NETWORK_TESTS=1 to skip the network tests.

Zebra may be unreliable on Testnet, and under less-than-perfect network conditions. See our roadmap for details.

Disk Usage

Zebra uses up to 40 GB of space for cached mainnet data, and 10 GB of space for cached testnet data.

RocksDB cleans up outdated data periodically, and when the database is closed and re-opened.

Disk Troubleshooting

Zebra's state commits changes using RocksDB database transactions.

If you forcibly terminate Zebra, or it panics, any incomplete changes will be rolled back the next time it starts.

So Zebra's state should always be valid, unless your OS or disk hardware is corrupting data.

Known Issues

There are a few bugs in Zebra that we're still working on fixing:

• In rare cases, Zebra panics on shutdown #1678
  • See #2209 for an example.
  • These panics can be ignored, unless they happen frequently.
• Interrupt handler does not work when a blocking task is running #1351
  • Zebra should eventually exit once the task finishes. Or you can forcibly terminate the process.
• No Windows support #3801
  • We used to test with Windows Server 2019, but not anymore; see issue for details

Future Work

In 2022, we intend to start adding RPC support and start adding wallet integrations. This phased approach allows us to test Zebra's independent implementation of the consensus rules, before asking users to entrust it with their funds.

Features:

• RPC functionality
• Wallet functionality

Performance and Reliability:

• Reliable syncing on Testnet
• Reliable syncing under poor network conditions
• Additional batch verification
• Performance tuning

Currently, the following features are out of scope:

• Mining support
• Optional Zcash network protocol messages
• Consensus rules removed before Canopy activation (Zebra checkpoints on Canopy activation)

Documentation

The Zebra website contains user documentation, such as how to run or configure Zebra, set up metrics integrations, etc., as well as developer documentation, such as design documents. We also render API documentation for the external API of our crates, as well as internal documentation for private APIs.

Security

Zebra has a responsible disclosure policy, which we encourage security researchers to follow.

License

Zebra is distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-APACHE and LICENSE-MIT.