Wallet addresses

At the heart of all interactions in Open Payments (OP) is an OP-enabled account. Every OP-enabled account is identified by one or more URLs. These URLs are not only account identifiers, but also service endpoints for gaining access to the OP API. These URLs are called wallet addresses. Not all URLs are wallet addresses, but all wallet addresses are URLs.

A URL is only a wallet address if the:

• Server handling the HTTP requests to the URL supports the OP protocol
• URL uses the https protocol and has no user-info, port, query string, or fragment parts

The quickest way to test if a URL is a wallet address is to make an HTTP GET request to the URL with an Accept header value of application/json.

curl --request GET \
   --url https://wallet.example.com/alice \
   --header 'accept: application/json'

If the URL is a wallet address, the response will provide details about the underlying OP-enabled account, including the URL of the grant request endpoint (the authServer). The grant request endpoint is used to get access tokens to connect to the account via the OP API.

HTTP/1.1 200 Success
Content-Type: application/json

{
  "id": "https://wallet.example.com/alice",
  "publicName": "Alice",
  "assetCode": "USD",
  "assetScale": 2,
  "authServer": "https://auth.wallet.example.com"
}

Privacy and security

A wallet address acts as a proxy identifier (alias) for an underlying financial account. If permitted by an account servicing entity (ASE), a single account can have multiple wallet addresses. Allowing account holders to generate unique wallet addresses for every client they interact with can help prevent a single address from becoming a tracking vector.

In addition to the “one account to one wallet address” and “one account to multiple wallet addresses” models, an ASE can allow a single wallet address to represent all of a user’s accounts. For example, imagine a user has three accounts with a digital wallet provider. The provider issues the user a single wallet address. When a payment is sent to the wallet address, the provider determines which one of the three accounts should receive the payment based on the currency type or some other agreed upon criteria.

Ultimately, it’s up to the ASE to define the supported configuration of relationships between wallet addresses and user accounts. This loose coupling allows wallet addresses to be disabled or even linked to a new account (although there are considerations that must be made before allowing this) without affecting the underlying account.

For any client, a wallet address is as good as an account. Any two distinct wallet addresses should be treated as distinct accounts by clients even if the client is aware that they are proxies for the same underlying account. Permission for a client to access an account via one wallet address is not automatically granted when accessing the same account via another wallet address.

Discovery and interaction

Using URLs as payment instruments solves two of the biggest issues with existing payments UX: discoverability and interaction.

URLs (universal resource locators) have been used on the web for decades to allow clients to directly locate a resource and begin interacting with it via HTTP. A wallet address is both a proxy identifier and a resource locator for the underlying account, used to access the account via the OP API and begin interactions with the account’s ASE.

Using URLs as proxies is also preferable to overloading other identifiers, such as email addresses and Mobile Station International Subscriber Directory Numbers (MSISDNs), as these proxies have no standard for interaction. As a result, identifiers like an MSISDN or email require a registry that maps the identifier to an account provider and a mechanism for governing this mapping securely.