| Independent Stream | F. Dold |
| Internet-Draft | Taler Systems SA |
| Intended status: Informational | C. Grothoff |
| Expires: May 7, 2020 | BFH |
| November 04, 2019 |
The 'payto' URI scheme for payments
draft-dold-payto-09
This document defines the 'payto' Uniform Resource Identifier (URI) scheme for designating targets for payments.
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This document defines the 'payto' Uniform Resource Identifier (URI) [RFC3986] scheme for designating transfer form data for payments. In particular, it always identifies the target of a payment. A 'payto' URI consists of a payment target type, a target identifier and optional parameters such as an amount or a payment reference.
The interpretation of the target identifier is defined by the payment target type, and typically represents either a bank account or an (unsettled) transaction.
A unified URI scheme for all payment target types allows applications to offer user interactions with URIs that represent payment targets, simplifying the introduction of new payment systems and applications.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
This document uses the Augmented Backus-Naur Form (ABNF) of [RFC5234].
payto-URI = "payto://" authority path-abempty [ "?" opts ]
opts = opt *( "&" opt )
opt = (generic-opt / authority-specific-opt) "=" *pchar
generic-opt = "amount" / "receiver-name" / "sender-name" /
"message" / "instruction"
authority-specific-opt = ALPHA *( ALPHA / DIGIT / "-" / "." )
authority = ALPHA *( ALPHA / DIGIT / "-" / "." )
path-abempty = <path-abempty, see [RFC3986], Section 3.3>
pchar = <pchar, see [RFC3986], Appendix A.>
The authority component of a payment URI identifies the payment target type. The payment target types are defined in the "Payment Target Types" sub-registry, see Section 8.2. The path component of the URI identifies the target for a payment as interpreted by the respective payment target type. The query component of the URI can provide additional parameters for a payment. Every payment target type SHOULD accept the options defined in generic-opt. The default operation of applications that invoke a URI with the payto scheme MUST be to launch an application (if available) associated with the payment target type that can initiate a payment. If multiple handlers are registered for the same payment target type, the user SHOULD be able to choose which application to launch. This allows users with multiple bank accounts (each accessed the respective bank's banking application) to choose which account to pay with. An application SHOULD allow dereferencing a payto URI even if the payment target type of that URI is not registered in the "Payment Target Types" sub-registry. Details of the payment MUST be taken from the path and options given in the URI. The user SHOULD be allowed to modify these details before confirming a payment.
payto://iban/DE75512108001245126199?amount=EUR:200.0&message=hello INVALID (authority missing): payto:iban/12345
Applications MUST accept URIs with options in any order. The "amount" option MUST only occur at most once. Other options MAY be allowed multiple times, with further restrictions depending on the payment target type. The following options SHOULD be understood by every payment target type.
amount = [ currency ":" ] unit [ "." fraction ] currency = 1*ALPHA unit = 1*(DIGIT / ",") fraction = 1*(DIGIT / ",")
amount: The amount to transfer, including currency information if applicable. The format MUST be: [ISO4217] alphabetic code. The unit value MUST be smaller than 2^53. If present, the fraction MUST consist of no more than 8 decimal digits. The use of commas is optional for readability and they MUST be ignored.
receiver-name: Name of the entity that receives the payment (creditor).
sender-name: Name of the entity that makes the payment (debtor).
message: A short message to identify the purpose of the payment, which MAY be subject to lossy conversions (for example, due to character set encoding limitations).
instruction: A short message giving instructions to the recipient, which MUST NOT be subject to lossy conversions. Character set limitations allowed for such instructions depend on the payment target type.
Various payment systems use restricted character sets. An application that processes 'payto' URIs MUST convert characters that are not allowed by the respective payment systems into allowable character using either an encoding or a replacement table. This conversion process MAY be lossy, except for the instruction field.
To avoid special encoding rules for the payment target identifier, the userinfo component [RFC3986] is disallowed in payto URIs. Instead, the payment target identifier is given as an option, where encoding rules are uniform for all options.
Interactive applications handling the payto URI scheme MUST NOT initiate any financial transactions without prior review and confirmation from the user, and MUST take measures to prevent clickjacking [HMW12].
Unless a payto URI is received over a trusted, authenticated channel, a user might not be able to identify the target of a payment. In particular due to homographs [unicode-tr36], a payment target type SHOULD NOT use human-readable names in combination with unicode in the target account specification, as it could give the user the illusion of being able to identify the target account from the URI.
To avoid unnecessary data collection, payment target types SHOULD NOT include personally identifying information about the sender of a payment that is not essential for an application to conduct a payment.
IANA maintains a registry called the "Uniform Resource Identifier (URI) Schemes" registry.
IANA maintains a sub-registry of the "Uniform Resource Identifier (URI) Schemes" registry also called the "Uniform Resource Identifier (URI) Schemes" registry. The "payto" URI scheme is already registered in this sub-registry with status set to "provisional" [RFC7595]. IANA is requested to update the reference for the "payto" URI scheme to reference the RFC number of this document when it is published as an RFC.
IANA is requested to create a new sub-registry of the "Uniform Resource Identifier (URI) Schemes" registry called the "Payment Target Types" registry with this document as the reference.
The sub-registry shall record for each entry: [RFC5226]. When requesting new entries, careful consideration of the following criteria is strongly advised:
The registration policy for this sub-registry is "First Come First Served", as described in
IANA is requested to populate the new sub-registry with the entries documented in the following sub-sections.
| [BIC] | International Organization for Standardization, "ISO 9362:2014 Business Identifier Code (BIC)", March 2019. |
| [BIP0021] | Schneider, N. and M. Corallo, "Bitcoin Improvement Proposal 21", January 2012. |
| [HMW12] | Huang, L., Moshchuk, A., Wang, H., Schecter, S. and C. Jackson, "Clickjacking: Attacks and Defenses", January 2012. |
| [ILP-ADDR] | Interledger Team, "ILP Addresses - v2.0.0", September 2018. |
| [UPILinking] | National Payment Corporation of India, "Unified Payment Interface - Common URL Specifications For Deep Linking And Proximity Integration", May 2016. |