This lightweight SDK connects Android to Zcash. It welds together Rust and Kotlin in a minimal way, allowing third-party Android apps to send and receive shielded transactions easily, securely and privately.
From an app developer's perspective, this SDK will encapsulate the most complex aspects of using Zcash, freeing the developer to focus on UI and UX, rather than scanning blockchains and building commitment trees! Internally, the SDK is structured as follows:
At a high level, this SDK simply helps native Android codebases connect to Zcash's Rust crypto libraries without needing to know Rust or be a Cryptographer. Think of it as welding. The SDK takes separate things and tightly bonds them together such that each can remain as idiomatic as possible. It's goal is to make it easy for an app to incorporate shielded transactions while remaining a good citizen on mobile devices.
Given all the moving parts, making things easy requires coordination. The [Synchronizer](docs/-synchronizer/README.md) provides that layer of abstraction so that the primary steps to make use of this SDK are simply:
To accomplish this, these responsibilities of the SDK are divided into separate components. Each component is coordinated by the [Synchronizer](docs/-synchronizer/README.md), which is the thread that ties it all together.
| **LightWalletService** | Service used for requesting compact blocks |
| **CompactBlockStore** | Stores compact blocks that have been downloaded from the `LightWalletService` |
| **CompactBlockProcessor** | Validates and scans the compact blocks in the `CompactBlockStore` for transaction details |
| **OutboundTransactionManager** | Creates, Submits and manages transactions for spending funds |
| **Initializer** | Responsible for all setup that must happen before synchronization can begin. Loads the rust library and helps with key derivation. |
| **RustBackend** | Wraps the rust library and exposes its functionality to the Kotlin SDK |
Importing the dependency should be enough for use but in the event that you want to compile the SDK from sources, including the Kotlin and Rust portions, simply use Gradle.
Compilation requires `Cargo` and has been tested on Ubuntu, MacOS and Windows. To compile the SDK run:
This creates a `testnet` build of the SDK that can be used to preview basic functionality for sending and receiving shielded transactions. If you do not have `Rust` and `Cargo` installed, the build script will let you know and provide further instructions for installation. Note that merely using the SDK does not require installing Rust or Cargo--that is only required for compilation.
This project follows [semantic versioning](https://semver.org/) with pre-release versions. An example of a valid version number is `1.0.4-alpha11` denoting the `11th` iteration of the `alpha` pre-release of version `1.0.4`. Stable releases, such as `1.0.4` will not contain any pre-release identifiers. Pre-releases include the following, in order of stability: `alpha`, `beta`, `rc`. Version codes offer a numeric representation of the build name that always increases. The first six significant digits represent the major, minor and patch number (two digits each) and the last 3 significant digits represent the pre-release identifier. The first digit of the identifier signals the build type. Lastly, each new build has a higher version code than all previous builds. The following table breaks this down:
| **alpha** | **Sandbox.** For developers to verify behavior and try features. Things seen here might never go to production. Most bugs here can be ignored.| Unstable: Expect bugs | Internal developers | 0XX | 1.2.3-alpha04 (10203004) |
| **beta** | **Hand-off.** For developers to present finished features. Bugs found here should be reported and immediately addressed, if they relate to recent changes. | Unstable: Report bugs | Internal stakeholders | 2XX | 1.2.3-beta04 (10203204) |
| **release candidate** | **Hardening.** Final testing for an app release that we believe is ready to go live. The focus here is regression testing to ensure that new changes have not introduced instability in areas that were previously working. | Stable: Hunt for bugs | External testers | 4XX | 1.2.3-rc04 (10203404) |
| **production** | **Dellivery.** Deliver new features to end users. Any bugs found here need to be prioritized. Some will require immediate attention but most can be worked into a future release. | Stable: Prioritize bugs | Public | 8XX | 1.2.3 (10203800) |