PaySwarm Authority client library.
Last updated 8 years ago by davidlehn .
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The PaySwarm Client API enables software to interact with a PaySwarm Authority. This includes registering public/private keypairs, performing purchases, depositing money, and withdrawing money into a bank account.

When writing software intended to act as a PaySwarm Buyer (something that makes purchases on the Web) or PaySwarm Vendor (something that sells stuff on the Web), the developer must do the following:

  1. Implement application-specific hooks for fetching documents from the Web, caching those documents, and storing sensitive data.
  2. Create a white-list of all trusted PaySwarm Authorities.
  3. Implement the public/private key-pair creation and registration UI.
  4. If creating buyer software, implement the software purchasing UI and calls to process the purchase via a PaySwarm Authority.
  5. If creating vendor software, implement the software sales UI, asset and listing creation UI, and all the calls to initiate a purchase via a PaySwarm Authority.

Implementing Hooks

Various hooks will be triggered when making calls to the API. Most of the hooks involve providing the API with a custom mechanism for doing HTTP GET/POST and storing/retrieving data from a database. It is also highly recommended that the optional cache hooks be implemented to prevent excessive network traffic when looking up PaySwarm Authority configurations and public keys. To implement a hook, simply write a function that takes the appropriate parameters and returns the appropriate values. Then pass the hook name and the name of the custom function to 'payswarm.addHook'. Look below for the specific hooks that must be implemented.

Importing the Client

At the top of your implementation, require the PaySwarm Client API:

var payswarm = require('payswarm-client');

Adding Trusted PaySwarm Authorities

Add the PaySwarm Authorities that should be trusted by calling:


In this version of the API, any PaySwarm Authority that the software will interact with must be manually added. A vendor's chosen PaySwarm Authority will be automatically added during the registration step. In the future, there will be a registry of trusted PaySwarm Authorities.

Performing a Purchase

Vendor Registration

If you are implementing a website that will operate as a PaySwarm Vendor (a piece of software that is selling something on the Web), you may register the vendor by calling:

var url = payswarm.getRegisterVendorUrl(

The first parameter is the host and port of the PaySwarm Authority to register with. The second is a callback URL that will receive the result of the registration as POST data.

Direct the vendor to the URL so that they can complete the registration process. Once the registration process is complete, the vendor's browser will POST the registration result to the callback URL provided.

On the callback page, get the POST value 'encrypted-message' and pass it to register the vendor:

payswarm.registerVendor(req.body['encrypted-message'], callback);

If no error is given to the callback, registration is complete. The second callback parameter is the PaySwarm Vendor's Preferences, including the Financial Account ID to use in Listings.

Creating Assets and Listings

Create a JSON-LD PaySwarm Asset and Listing. When listing an Asset, its unique hash must be in the Listing. To generate an asset hash call:

payswarm.hash(asset, callback);

Sign a listing. Create a JSON-LD PaySwarm Listing and then sign it:

payswarm.sign(listing, callback);

Display the listing information; the use of RDFa is recommended. Depending on the application's needs, it is sometimes a good idea (or a requirement) to regenerate signatures when the vendor's public key is changed.

Note: A Listing also contains a License for the Asset. If the application knows the ID (IRI) of the License to use but not the License hash, and it does not have the necessary parser to obtain the License information from its ID, it may use the PaySwarm Authority's license service to cache and retrieve the License by its ID. Then payswarm.hash(license, callback) can be called on the result to produce its hash.

Performing a Vendor-initiated Purchase

When a customer indicates that they want to purchase the Asset in a Listing, call:

var url = payswarm.getPurchaseUrl(

To get a URL to redirect the customer to their PaySwarm Authority to complete the purchase. The last parameter is a callback URL that will receive the result of the purchase as POST data.

If the customer has previously completed a purchase and the response indicated that they set up a budget to handle automated purchases in the future, then an automated purchase can be attempted by calling:


In this version of the API, it is the responsibility of the application to determine the customer's PaySwarm Authority (usually by asking). A listing hash can be generated by calling:

payswarm.hash(listing, callback);

To get the JSON-LD receipt from a purchase, call:

payswarm.getReceipt(encryptedMessage, callback);

Where encryptedMessage is either the result of a POST to the purchase callback or the result of the payswarm.purchase() call.

The receipt will indicate the ID and hash of the Asset purchased as well as the ID and hash of the License for the Asset.


This software was written by Digital Bazaar and friends. Please see the AUTHORS file for full credits.


The payswarm.js code, tools, and examples are available under a BSD 3-Clause License. Please see the LICENSE file for full details.

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