Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.¶

This is a contribution to the RFC Series, independently of any other RFC stream. The RFC Editor has chosen to publish this document at its discretion and makes no statement about its value for implementation or deployment. Documents approved for publication by the RFC Editor are not candidates for any level of Internet Standard; see Section 2 of RFC 7841.¶

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8905.¶

Copyright Notice

Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved.¶

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document.¶

Table of Contents

1. Introduction

This document defines the 'payto' Uniform Resource Identifier (URI) [RFC3986] scheme for designating transfer form data for payments.¶

2. Syntax of a 'payto' URI

This document uses the Augmented Backus-Naur Form (ABNF) of [RFC5234].¶

  payto-URI = "payto://" authority path-abempty [ "?" opts ]
  opts = opt *( "&" opt )
  opt-name = generic-opt / authority-specific-opt
  opt-value = *pchar
  opt = opt-name "=" opt-value
  generic-opt = "amount" / "receiver-name" / "sender-name" /
                "message" / "instruction"
  authority-specific-opt = ALPHA *( ALPHA / DIGIT / "-" / "." )
  authority = ALPHA *( ALPHA / DIGIT / "-" / "." )

'path-abempty' is defined in Section 3.3 of [RFC3986]. 'pchar' is defined in Appendix A of [RFC3986].¶

3. Semantics

The authority component of a payment URI identifies the payment target type. The payment target types are defined in the "Payto Payment Target Types" registry (see Section 10). 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 via 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 "Payto Payment Target Types" 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.¶

4. Examples

Valid Example:¶

payto://iban/DE75512108001245126199?amount=EUR:200.0&message=hello

Invalid Example (authority missing):¶

payto:iban/12345

5. Generic Options

Applications MUST accept URIs with options in any order. The "amount" option MUST NOT occur more than 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:

The amount to transfer. The format MUST be:¶

  amount = currency ":" unit [ "." fraction ]
  currency = 1*ALPHA
  unit = 1*(DIGIT / ",")
  fraction = 1*(DIGIT / ",")

¶

If a 3-letter 'currency' is used, it MUST be an [ISO4217] alphabetic code. A payment target type MAY define semantics beyond ISO 4217 for currency codes that are not 3 characters. 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). The value of this option MAY be subject to lossy conversion, modification, and truncation (for example, due to line wrapping or character set conversion).¶

sender-name:

Name of the entity that makes the payment (debtor). The value of this option MAY be subject to lossy conversion, modification, and truncation (for example, due to line wrapping or character set conversion).¶

message:

A short message to identify the purpose of the payment. The value of this option MAY be subject to lossy conversion, modification, and truncation (for example, due to line wrapping or character set conversion).¶

instruction:

A short message giving payment reconciliation instructions to the recipient. An instruction that follows the character set and length limitation defined by the respective payment target type SHOULD NOT be subject to lossy conversion.¶

6. Internationalization and Character Encoding

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 characters using either an encoding or a replacement table. This conversion process MAY be lossy, except for the instruction field. If the value of the instruction field would be subject to lossy conversion, modification, or truncation, the application SHOULD refuse further processing of the payment until a different value for the instruction is provided.¶

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.¶

Defining a generic way of tagging the language of option fields containing natural language text (such as "receiver-name", "sender-name", and "message) is out of the scope of this document, as internationalization must accommodate the restrictions and requirements of the underlying banking system of the payment target type. The internationalization concerns SHOULD be individually defined by each payment target type.¶

7. Tracking Payment Target Types

A registry of "Payto Payment Target Types" is described in Section 10. The registration policy for this registry is "First Come First Served", as described in [RFC8126]. When requesting new entries, careful consideration of the following criteria is strongly advised:¶

1. The description clearly defines the syntax and semantics of the payment target and optional parameters if applicable.¶
2. Relevant references are provided if they are available.¶
3. The chosen name is appropriate for the payment target type, does not conflict with well-known payment systems, and avoids potential to confuse users.¶
4. The payment system underlying the payment target type is not fundamentally incompatible with the general options (such as positive decimal amounts) in this specification.¶
5. The payment target type is not a vendor-specific version of a payment target type that could be described more generally by a vendor-neutral payment target type.¶
6. The specification of the new payment target type remains within the scope of payment transfer form data. In particular, specifying complete invoices is not in scope. Neither are processing instructions to the payment processor or bank beyond a simple payment.¶
7. The payment target and the options do not contain the payment sender's account details.¶

Documents that support requests for new registry entries should provide the following information for each entry:¶

Name:

The name of the payment target type (case-insensitive ASCII string, restricted to alphanumeric characters, dots, and dashes).¶

Description:

A description of the payment target type, including the semantics of the path in the URI if applicable.¶

Example:

At least one example URI to illustrate the payment target type.¶

Contact:

The contact information of a person to contact for further information.¶

References:

Optionally, references describing the payment target type (such as an RFC) and target-specific options or references describing the payment system underlying the payment target type.¶

This document populates the registry with seven entries as follows (see also Section 10).¶

8. Security Considerations

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.¶

The authentication/authorization mechanisms and transport security services used to process a payment encoded in a 'payto' URI are handled by the application and are not in scope of this document.¶

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.¶

9. IANA Considerations

IANA maintains the "Uniform Resource Identifier (URI) Schemes" registry, which contains an entry for the 'payto' URI scheme as follows. IANA has updated that entry to reference this document.¶

Scheme name:

payto¶

Status:

provisional¶

URI scheme syntax:

See Section 2 of RFC 8905.¶

URI scheme semantics:

See Section 3 of RFC 8905.¶

Applications/protocols that use this scheme name:

payto URIs are mainly used by financial software.¶

Contact:

Christian Grothoff <grothoff@gnu.org>¶

Change controller:

Christian Grothoff <grothoff@gnu.org>¶

References:

See Section 11 of RFC 8905.¶

10. Payto Payment Target Types

This document specifies a list of payment target types. It is possible that future work will need to specify additional payment target types. The GNUnet Assigned Numbers Authority (GANA) [GANA] operates the "Payto Payment Target Types" registry to track the following information for each payment target type:¶

Name:

The name of the payment target type (case-insensitive ASCII string, restricted to alphanumeric characters, dots, and dashes)¶

Contact:

The contact information of a person to contact for further information¶

References:

Optionally, references describing the payment target type (such as an RFC) and target-specific options or references describing the payment system underlying the payment target type¶

The entries in the "Payto Payment Target Types" registry defined in this document are as follows:¶

11. References

Authors' Addresses