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Web Payment APIs A short talk on Web Payment APIs https://captnemo.in/talks/webpayments/

Web Payment APIs

- nemo (RFCs We Love, May 2020)

whoami

TODO

webpayments

The goal is to create a safe, decentralized system and a set of open, patent and royalty-free specifications that allow people on the Web to send each other money as easily as they exchange instant messages and e-mail today.

W3C

  • ActivityPub
  • CGI
  • CSS
  • DOM
  • HTML
  • RDF
  • SOAP
  • SPARQL
  • SVG
  • XHTML
  • XML
  • XPath

demo

Before we start, let's do a quick demo of how it all comes together.

specifications*

See github.com/w3c/webpayments/wiki for a complete list

* working drafts

specifications*

the talk

Try to understand how we can complete a payment entirely from within your browser without relying on any proprietary APIs (as a processor/merchant), and yet being compatible with any payment instrument.

definitions

The payment method: the means that the payer uses to pay the payee (e.g., a basic card payment). They are uniquely identified via a Payment Method Identifier (PMI)

The payment method provider establishes the ecosystem to support that payment method.

The details of how to fulfill a payment request for a given payment method is an implementation detail of a payment handler, which is a Web application that can handle a request for payment on behalf of the user.

examples

payment method: Paytm Wallet Account, UPI, Card, Gift Card, Voucher Code, Bitcoin.

Payment Method Identifier: https://paytm.com, https://npci.org.in/upi, basic-card

payment method provider: Razorpay, Stripe, PayPal, NPCI/UPI, your-bank-goes-here

Payment Method Identifier

  • URL-based payment method identifier (say, https://bitcoincore.org/ or https://pay.wechat.com).
  • or a standardized payment method identifier (currently only basic-card is on the registry).

humanized: how to identify and categorize various payment methods?

Payment Method Manifest

allows the curators of a defined payment method or owners of a proprietary payment method to authorize (via a manifest file) which payment handlers may be used to fulfill the payment method.

humanized: defines the schema of a specific payment method. The one for basic-card is standardized in a specification already.

How to get to the manifest?

GET / HTTP/2
Host: alicepay.com

HTTP/2 204
Link: </pay/payment-manifest.json>; rel="payment-method-manifest"

What's inside a Manifest?

A payment method manifest tells the user-agent "how to process payments for a particular method".

URL: https://alicepay.com/pay/payment-manifest.json

{
  "default_applications": ["app/webappmanifest.json"],
  "supported_origins": [
    "https://bobpay.xyz",
    "https://alicepay.friendsofalice.example"
  ]
}

user-agent can go next to https://alicepay.com/pay/app/webappmanifest.json to install the AlicePay application.

supported_origins defines which origins can be trusted to install an application for this payment method.

What's inside a Manifest (1)

{
  //...
  "supported_origins": [
    "https://beta.alicepay.com",
    "https://bobpay.com"
  ]
}

A payment application hosted at either alicepay.com, beta.alicepay.com, or bobpay.com is now authorized for the payment method https://alicepay.com.

What's inside a Manifest (2)

{
  //...
  "supported_origins": "*"
}

any third party is allowed to support the payment method.

recap

So far, the user-agent has done the following:

  1. seen a payment-method (we haven't gotten to how)
  2. discovered the payment method manifest URL
  3. parsed the payment method manifest to determine the webapp manifest URL
  4. fetched the webapp manifest URL
  5. installed the payment method's application(s)

The application installation is based on W3C's Web App Manifest specification.

Payment Handler

Each payment handler defines:

  1. Steps to check if a payment can be made:
  2. Steps to respond to a payment request:

The structure of this object is specific to each payment method.

  1. Steps for when a user changes payment method (optional)

Steps that describe how to handle the user changing payment method or monetary instrument (e.g., from a debit card to a credit card)

overview

TODO: Move this higher?

ref

Payment Request API

Future Scope

  • Installing a payment app is clunky, maybe we can just install the service-worker directly.

references