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README.md

CIP Title Authors Comments-URI Status Type Created License
13
Cardano URI Scheme
Sebastien Guillemot <sebastien@emurgo.io>, Vicente Almonacid <vicente@emurgo.io>, Robert Phair <rphair@cosd.com>
Draft
Informational
2020-09-22
CC-BY-4.0

Abstract

This proposal describes a basic URI scheme to handle Ada transfers and links to single stake pools or weighted lists of multiple pools.

Motivation

For payment URIs:

Users who create community content often want donations as a financial incentive. However, forcing users to open their wallet and copy-paste an address lowers the amount of people likely to send tokens (especially if they have to sync their wallet first).

If donating was as simple as clicking a link that opens a light wallet with pre-populated fields, users may be more willing to send tokens. URI schemes would enable users to easily make payments by simply clicking links on webpages or scanning QR Codes.

For stake pool URIs:

Centralised sources of information have led a growing amount of stake to be disproportionately assigned to pools pushed near & beyond the saturation point.

Stake pool URIs will provide an additional means for small pools to acquire delegation and maintain stability, supporting diversity and possibly fault-tolerance in the Cardano network through a more even distribution of stake.

Interfaces that connect delegators with pools beyond the highly contested top choices of the in-wallet ranking algorithms are important to avoid saturation and maintain decentralization.

Larger pools and collectives can also use these URIs to link to, and spread delegation between, a family of pools they own to avoid any one of their pools becoming saturated.

Pool links allow for interfaces to initiate delegation transactions without requiring any code modifications to the wallets themselves.

URIs for weighted stake pool lists provide alternatives to using a JSON file to implement delegation portfolios in a way that may better suit certain platforms, applications, or social contexts.

Specification

The core implementation should follow the BIP-21 standard (with bitcoin: replaced with web+cardano:)

Rationale:

  • Use cardano: over ada: as other projects that implement this standard tend to take the project name over the currency name (this makes sense if we consider this protocol as a generic way for interacting with the blockchain through wallets - as opposed to a simple payment system)
  • Many wallets support multiple currencies. Following the same standard will ensure higher adoption of our protocol.

Examples:

<a href="web+cardano:Ae2tdPwUPEZ76BjmWDTS7poTekAvNqBjgfthF92pSLSDVpRVnLP7meaFhVd">Donate</a>
<a href="web+cardano://stake?c94e6fe1123bf111b77b57994bcd836af8ba2b3aa72cfcefbec2d3d4">Stake with us</a>
<a href="web+cardano://stake?POOL1=3.14159&POOL2=2.71828">Split between our 2 related pools</a>
<a href="web+cardano://stake?COSD">Choose our least saturated pool</a>

Considerations

  1. BIP-21 is limited to only features Bitcoin supports. A similar feature for Ethereum would, for example, also support gas as an extra parameter. BIP-21 is easily extensible but we have to take precaution to avoid different wallets having different implementations of these features as they become available on Cardano. To get an idea of some extra features that could be added, consider this (still under discussion) proposal for Ethereum: EIP-681

  2. Depending on the protocol registration method (see next section), browsers generally enforce a web+ or ext+ prefix for non-whitelisted protocols (note: bitcoin: was whitelisted). The prefix ext+ is recommended for extensions, but not mandatory.

ABNF Grammar (Proposal)

This is an initial, simplified protocol definition for fast implementation; it only requires:

  • for a payment URI (authority unspecified), an address and an optional amount parameter;
  • for a stake pool URI (authority = stake), a weighted list of one or more stake pools.

As discussed above, these rules are likely to evolve in order to support other capabilities of the Cardano blockchain.

cardanourn = "web+cardano:" (paymentref | stakepoolref)

paymentref = cardanoaddress [ "?" amountparam ]
cardanoaddress = *(base58 | bech32)
amountparam = "amount=" *digit [ "." *digit ]

stakepoolref = "//stake" stakequery
stakequery = ( "?" stakepoolpair) *( "&" stakepoolpair)
stakepoolpair = stakepool [ "=" proportion]

stakepool = poolhexid | poolticker
poolhexid = 56HEXDIG
poolticker = 3*5UNICODE

proportion = *digit [ "." *digit ]

Payment URI queries

The amount parameter must follow the same rules described in BIP-21, namely, it must be specified in decimal ADA, without commas and using the period (.) decimal separator.

Stake pool URI queries

For brevity, essential in many Internet contexts, poolticker must be supported here in addition to the unambiguous poolhexid.

When there is more than one pool registered with any of the specified poolticker parameters (whether for pool groups which have the same ticker for all pools, or for separate pools using the same ticker), the choice to which pool(s) to finally delegate is left to the user through the wallet UI.

Interpretation of proportion:

  • If only one stake pool is specified, any proportion is meaningless and ignored.
  • If all stake pools have a numerical proportion, each component of the resulting stake distribution will have the same ratio as the provided proportion to the sum of all the propotions.
  • Any missing proportion is assigned a precise value of 1.
  • If a stake pool is listed multiple times, the URI is rejected as invalid.

Handling stake pool links

The wallet UI should always confirm the exact delegation choice even when it is unambiguous from the URI. When the user has multiple wallets, the wallet UI must select which wallet(s) the user will be delegating from.

If, during a wallet or other application's development process, it is still only able to support single pool links, these parameters in the URI query string should (by preference of the wallet UI designers) either be ignored or generate a warning message, to avoid leading the user to believe they are implementing a currently unsupported but perhaps popularly referenced multi-pool delegation list:

  • any value for the first URI query argument;
  • any URI query argument beyond the first.

Security Considerations

  1. For payment links, we cannot prompt the user to send the funds right away as they may not be fully aware of the URI they clicked or were redirected to. Instead, it may be better to simply pre-populate fields in a transaction.
  2. For either payment or staking links, we should be wary of people who disguise links as actually opening up a phishing website that LOOKS like that corresponding part of the wallet UI.
  3. If wallets create stake pool links, the actual ada or lovelace balance should not be used literally as the proportion figure, to avoid revealing the identity of the wallet owner who is creating the portfolio (e.g. the proportions could be scaled to normalise the largest to 1).

Rationale

Why not use Universal links, deep links and other non-protocol-based Solution

An alternative solution to the original problem described above is to use standard URL links in combination with a routing backend system. The routing system is used to redirect to the app's URI. The advantage of this scheme is that it allows to provide a fallback mechanism to handle the case when no application implementing the protocol is installed (for instance, by redirecting to the App Store or Google Play). This is the approach behind iOS Universal Links and Android App Links. In general, it provides a better user experience but requires a centralized system which makes it unsuitable for as a multi-app standard.

How URI delegation portfolio links supplement use of JSON files for the same purpose

URIs facilitate the "social element" of delegated staking and pool promotion through a socially familiar, easily accessible, and less centralised convention for sharing stake pool references and potential delegation portfolios without having to construct or host a JSON file.

The processing of a JSON file delivered by a web server will depend highly on a user's platform and might not even be seen by the wallet application at all. With a properly associated web+cardano: protocol, developers and users have another option available in case JSON files are not delivered properly to the wallet application.

Read More

https://developer.mozilla.org/en-US/docs/Web/API/Navigator/registerProtocolHandler

https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/protocol_handlers

https://developer.android.com/training/app-links/deep-linking#adding-filters

https://facebook.github.io/react-native/docs/linking.html

https://developer.apple.com/documentation/uikit/core_app/allowing_apps_and_websites_to_link_to_your_content/defining_a_custom_url_scheme_for_your_app

https://en.wikipedia.org/wiki/Augmented_Backus%E2%80%93Naur_form

https://tools.ietf.org/html/draft-seantek-unicode-in-abnf-00

cardano-foundation#82