Creating equitable access to the global financial system
The Anchor Platform is the easiest and fastest way to deploy a SEP-compatible anchor service.
It implements the majority of standardized API (SEP) endpoints that wallets, exchanges, and other applications use, and provides a set of backend HTTPS APIs & callbacks for the anchor to integrate with for specifying fees, exchange rates, and off-chain transaction status updates.
The goal of the Anchor Platform is to abstract all Stellar-specific functionality and requirements for running an anchor, allowing businesses to focus on the core business logic necessary to provide these services.
The full documentation can be found under the docs directory, under the structure:
- 00 - Stellar Anchor Platform
- 01 - Running & Configuring the Application
- 02 - Contributing
- 03 - Implementing the Anchor Server
- 04 - Subprojects Usage
// In progress...
Here are the important terminology used in this project:
- Anchor: on/off ramps of the Stellar network. More information is available here.
- Wallet: a frontend application used to interact with the Stellar network on behalf of a user.
- Sending Anchor: a therminology used in the context of SEP-31. Refers to an entity that receives funds from a user and forwards it (after taking a fee) to a receiving anchor, in the SEP-31
Sending Client->Sending Anchor->Receiving Anchor-> Receiving Clientflow. - Receiving Anchor: a terminology used in the context of SEP-31. Refers to an entity that receives funds from a user and forwards it (after taking a fee) to a receiving client (or recipient), in the SEP-31
Sending Client->Sending Anchor->Receiving Anchor-> Receiving Clientflow. This is what the Anchor Platform currently implements. - Ecosystem: the community of entities and users that utilize the Stellar network and/or provide solutions on the Stellar network.
- Anchor Platform (or Platform): the web application that will be exposing public endpoints and APIs. It is compliant with the SEPs to guarantee interoperability in the Stellar network and delegates business-specific logic to the Anchor Server.
- Anchor Server: a microservice that will be responsible for the Anchor-specific business logic used in the the Anchor Platform. This service interacts with the Anchor Platform to perform some actions like:
- Calculate conversion rates between two assets.
- Create or update a customer account.
- Notify the Anchor about an incoming payment.
- Anchor Reference Server: an Anchor Server implementation that is shipped as part of this repository for testing purposes.
- Callback API (
Sync Platform->Anchor): a syncronous API that the Platform will use to gather a business-specific data from the Anchor Server, in order to perform a SEP-compliant operation (like exchange rate or user registration, for instance) - Events Queue (
Async Platform->Anchor): an asyncronous communication venue that the Platform will use to notify the Anchor Server about a pending action, like an incoming payment that needs to be processed. - Platform API (
Sync Anchor->Platform): a syncronous API that the Anchor can use to fetch information (e.g. transactions or quotes) and also update the data of transactions stored in the Platform database. - SEPs: it means Stellar Ecosystem Proposals and refers to standards that are used by Stellar ecosystem participants to achieve interoperability in the network. The ones implemented by this project are:
Standard Description Configurable Interacts with Anchor Server Supported by the Platform API Supported by the SDK SEP-10 Handles authentication. YES NO YES YES SEP-12 Handles KYC. YES YES YES YES SEP-24 Handles deposit & withrawal of assets in/out the Stellar network. YES NO No YES SEP-31 Used for international remittances. Only the receiver side is implemented. YES YES YES YES SEP-38 Used for rfq in conjunction with SEP-31. YES YES YES YES
In order to deploy this project, you'll need to have the following microservices running:
- Database Server: usually, you'll use a relational database like MySQL or PostgreSQL, but we also support SQLite, commonly used in local development.
- Queue Service: we currently support Kafka and Amazon SQS.
- Anchor Platform Server: this is the main application that will be providing public endpoints for your Anchor application.
- Anchor Server: this is the microservice that will be responsible for the Anchor-specific business logic used in the the Anchor Platform.
The following image shows the architecture of the Anchor Platform, as well as how it interacts with the Anchor Server and the Wallet/Client/Sending Anchor.
As you can see, the Anchor Platform receives interactions from ecosystem participants and deals with the interoperability part described in the SEPs. The Anchor Server is only called when there is a pending action to be performed.
This drastically reduces the amount of code that needs to be written by the Anchor, and allows them to focus on the business logic that's specific to their businesses and use cases.
Here you can see the sequence diagram of the SEP-31 flow, showing all the stakeholders, as well as the communication between Platform and Anchor Server. Please notice this flow includes quotes (SEP-38) but they may not be needed for your use-case:
%% Happy path SEP-31 transaction flow with new customers
%% View at: https://mermaid.live
%% Assumptions:
%% - The KYC information provided by the sender is valid on first attempt
%% - The client does not request customer status callbacks
%% - The anchor successfully delivers off-chain funds on first attempt
sequenceDiagram
title: SEP-31 Transaction Flow
participant Client
Note over Client: In the SEP-31 flow, this is the Sending Anchor.
participant Platform
Note over Platform: In the SEP-31 flow, this is the Receiving Anchor.
participant Anchor
participant Stellar
participant Recipient
Client->>+Platform: GET /.well-known/stellar.toml
Platform-->>-Client: SEP-10, 12 & 31 URLs
Client->>+Platform: GET [SEP-31]/info
Platform-->>-Client: assets, customer types, fees
Client->>+Platform: GET [SEP-10]
Platform-->>-Client: challenge transaction
Client-->>Client: signs challenge
Client->>+Platform: POST [SEP-10]
Platform-->>Platform: verifies challenge
Platform-->>-Client: authentication token
loop Sending and Receiving Customer
Client->>+Platform: GET [SEP-12]/customer?type=
Platform->>+Anchor: forwards request
Anchor-->>-Platform: fields required
Platform-->>Platform: updates customer status (NEEDS_INFO)
Platform-->>-Client: forwards response
Client-->>Client: collects fields
Client->>+Platform: PUT [SEP-12]/customer?type=
Platform->>+Anchor: forwards request
Anchor-->>Anchor: validates KYC values
Anchor-->>-Platform: id, ACCEPTED
Platform-->>Platform: updates customer status (ACCEPTED)
Platform-->>-Client: forwards response
end
opt Get a Quote if Supported or Required
Client->>+Platform: GET [SEP-38]/price
Platform->>+Anchor: GET /rate?type=indicative_price
Anchor-->>-Platform: exchange rate
Platform-->>-Client: exchange rate
Client-->>Client: confirms rate
Client->>+Platform: POST [SEP-38]/quote
Platform->>+Anchor: GET /rate?type=firm
Anchor-->>-Platform: exchange rate, expiration
Platform-->>Client: quote id, rate, expiration
Platform->>+Anchor: POST [webhookURL]/quote created
Anchor-->>-Platform: 204 No Content
end
Client->>+Platform: POST [SEP-31]/transactions
Platform-->>Platform: checks customer statuses, links quote
Platform->>+Anchor: GET /fee
Anchor-->>Anchor: calculates fee
Anchor-->>-Platform: fee
Platform-->>Platform: Sets fee on transaction
Platform-->>-Client: transaction id, receiving account & memo
Platform->>+Anchor: POST [webhookURL]/transactions created
Anchor-->>-Platform: 204 No Content
Client->>+Stellar: submit Stellar payment
Stellar-->>Platform: receives payment, matches w/ transaction
Platform-->>Platform: updates transaction status
Stellar-->>-Client: success response
Platform->>+Anchor: POST [webhookURL]/transactions received
Anchor-->>Anchor: queues off-chain payment
Anchor-->>-Platform: 204 No Content
Anchor->>Recipient: Sends off-chain payment to recipient
Anchor->>+Platform: PATCH /transactions
Platform-->>Platform: updates transaction to complete
Platform-->>-Anchor: updated transaction
Client->>+Platform: GET /transactions?id=
Platform-->>-Client: transaction complete
Client-->>Client: notifies sender
Note: in terms of database usage for SEP-31, our tests indicate that each SEP-31 (with SEP-38) transaction occupies ~2KB of space in the database. The tests also indicate the data space usage tends to decrease as the number of SEP-31 transactions increases. These results were achieved by executing 500 SEP-31 transactions on a Postgres database.
The Stellar Anchor SDK is a collection of projects that make easy to build financial applications on Stellar:
- api-schema: the API interfaces, request, response classes.
- core: the base package for implementing standardized anchor applications.
- payment: implementation of payment service with Circle API.
- platform: the anchor platform Spring Boot Application with WebMVC.
- anchor-reference-server: the reference implementation of the anchor server.
- service-runner: the runner class for the platform, reference server and payment observer.
- integration-tests: the integration tests for the platform, reference server, and payment observers.
While the project is in its early stages and in active development, it is used in production today by businesses providing services on Stellar.
To learn how to run and configure this project, please refer to 01.A - Running & Configuring the Application.
Please refer to our 0.2.A - CONTRIBUTING guide for more information on how to contribute to this project.