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Hyperledger Aries allows trusted online peer-to-peer interactions based on decentralized identities and verifiable credentials. Aries includes a protocol definition, tools, and reference implementations. The Aries protocol supports identities rooted in a variety of distributed ledgers or blockchains. This approach to identity is often called Self Soverign Identity (SSI).

Key components of an Aries solution are:

• agents,
• DID communications,
• protocols
• and key management

Getting Started

Aries is a young project that is maturing quickly. As such, be warned that the project documentation and links may get out of out-of-date. If you find there is something missing, please connect with the community on the Aries Hyperledger Discord Channel. And of course, pull requests are always welcome to fix things that are confusing!

If you are entirely new to the decentralized identity space and the Hyperledger projects there is a Linux Foundation edX course on decentralized identity and Hyperledger Indy, Aries and Ursa. Start there! A companion developers edX course is planned for "early" 2020.

If you know about decentralized identity and verifiable credentials and want to get started building applications on top of Aries (and Indy), the most consistently maintained guide for new developers is the one included in the Aries Cloud Agent Python (ACApy):

Repos

The Aries project contains a number of repos, which can be grouped into some important categories.

Aries Agent Frameworks

Developers who want to solve business problems (vs. contributing directly to Aries) should start with an Aries agent framework. Agent-based applications are created by adding application-specific code that control the Aries agent.

There are several Aries general purpose agent frameworks that are ready to go out of the box.

• Aries Cloud Agent - Python (ACA-Py) is suitable for all non-mobile agent applications and has production deployments. ACA-Py and a controller run together, communicating across an HTTP interface. Your controller can be written in any language and ACA-Py embeds the Indy-SDK.
• Aries Framework - .NET can be used for building mobile (via Xamarin) and server-side agents and has production deployments. The controller for an aries-framework-dotnet app can be written in any language supporting embedding the framework as a library in the controller. The framework embeds the Indy-SDK.
• Aries Static Agent - Python is a configurable agent that does not use persistent storage.

There are several other frameworks that are currently under active development, including:

• Aries Framework - Go is a pure golang framework that provides a similar architecture to ACA-Py, exposing an HTTP interface for its companion controller. The framework does not currently embed the Indy SDK and work on supporting a golang-based verifiable credentials implementation is in progress
• aries-sdk-ruby
• aries-framework-javascript

Development Tools and Test Suites

The Aries project provides some useful tools for developing agents and testing that they are compatible with other agents in the ecosystem.

• aries-toolbox
• aries-protocol-test-suite

Shared Libraries

Coming Soon There are also a set of shared open source libraries that provide C-callable APIs that can be used by agents and frameworks to support the Aries protocols.

• Aries Key Management: Functions for managing keys, including storage plugins.
• Aries Verifiable Data Registry Interface: An interface for verifying data agianst an underlying ledger.
• Aries Util: Utility functions for Aries communication, such as message packing.

While these are in development, the ACA-Py and .NET frameworks embed the Indy-SDK, while the Go framework is building the capabilities in golang.

Protocols

If you want to understand the theory and the open standards that these agents and frameworks implement, then you should refer to the Aries protocol documents:

• aries-rfcs

Project Participation

You can raise issues using the GitHub issue tracker in each Aries repository. Pull requests are appreciated; please review CONTRIBUTING.md for the repository to which you want to contribute.

You can reach other Aries developers:

• in the Discord channel #aries,
• on the mailing list,
• or in the Aries Working Group weekly call.

Relationship to Hyperledger Indy

Aries grew out of the work in Hyperledger Indy to create technologies for managing decentralized identity. Indy provides a specific blockchain purpose-built for identity. The tools created in Indy for building agents are being migrated to Aries, and extended to be blockchain-agnostic. Functionality related to the Indy ledger will remain in Indy.

If you want to start build decentralized identity capabilities around Indy, you should use the existing Aries Agent frameworks described above that embed the Indy SDK. If you are already using the Indy SDK to build a decentralized identity solution, you can keep using it knowing that it will continue to be maintained. If and when the Indy SDK is fully or partially deprecated, a transition process will be communicated.