Exonum

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Exonum is an extensible open-source framework for creating blockchain applications. Exonum can be used to create cryptographically powered distributed ledgers in virtually any problem domain, including FinTech, GovTech, and LegalTech. The Exonum framework is oriented towards creating permissioned blockchains, that is, blockchains with the known set of blockchain infrastructure providers.

If you are using Exonum in your project and want to be listed on our website & GitHub list — write us a line to contact@exonum.com.

Contents

This is the main Exonum repository containing the bulk of Rust crates used in Exonum. Rust crates for Exonum are intended to be reasonably small and reusable, hence there is relatively large number of them.

Main Crates

• Core library
• Node implementation
• Node CLI

Upstream Dependencies

• Cryptographic library
• Database backend for merkelized data structures
• Key management
• Derive macros
• Protobuf helpers
• Protobuf support for build scripts
• High-level HTTP API abstraction

Tools for Building Services

• Rust runtime
• Testing framework

Services and Node Plugins

• Explorer service and explorer library
• Middleware service
• Supervisor service
• Time oracle service
• System API plugin

Examples

• Cryptocurrency
• Advanced cryptocurrency
• Timestamping
• Sample runtime implementation

Versioning Policy

Exonum crates follow semantic versioning.

The exonum crate and its re-exported dependencies (exonum-crypto, exonum-merkledb and exonum-keys) are released at the same time; their version is considered the version of the Exonum framework. On the other hand, the crates downstream of exonum (e.g., exonum-node) or independent of it (e.g., exonum-api) may evolve at different speeds, including major releases not tied to a major Exonum release.

Throughout the Exonum codebase, certain APIs are described in the API docs as unstable or experimental. Such APIs may be removed or changed in a semantically non-breaking release (for example, a minor release) of the corresponding crate. Similarly, nominally public APIs that are hidden from the docs via #[doc(hidden)] are considered unstable and thus exempt from semantic versioning limitations.

Supported Rust Versions

The Exonum crates are built against a specific stable Rust version (1.42.0). Newer stable versions are supported as a result. (Feel free to file an issue if any Exonum crate does not build on a newer stable version.) Newer beta and nightly versions should be supported as well, but no specific effort is allocated into supporting them.

Due to at least some external dependencies not factoring the minimum supported Rust version into their semantic versioning policy, the Exonum crates effectively have no choice but to do the same. Namely, a bump of the minimum supported Rust version will not be considered a semantically breaking change. It is, however, guaranteed that the Exonum crates will build on some stable Rust.

Note that due to versioning policies of external dependencies, the effective minimum supported Rust version may increase as a result of the activities out of control of Exonum developers. The decision how to deal with this situation (pin the dependency or bump the minimum supported Rust version) will be made on the case-by-case basis.

Contributing

To contribute to Exonum, please see CONTRIBUTING.

See Also

Some Exonum stuff that is not in this repository:

• Java language support
• JavaScript light client
• Python light client
• High-level documentation
• Dynamic service launcher for Exonum