Internet Engineering Task Force F. Dold Internet-Draft Taler Systems SA Intended status: Informational C. Grothoff Expires: August 1, 2019 BFH January 28, 2019 The 'payto' URI scheme for payments draft-dold-payto-03 Abstract This document defines the 'payto' Uniform Resource Identifier (URI) scheme for designating targets for payments. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 1, 2019. Copyright Notice Copyright (c) 2019 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. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Dold & Grothoff Expires August 1, 2019 [Page 1] Internet-Draft The 'payto' URI scheme January 2019 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Syntax of a 'payto' URL . . . . . . . . . . . . . . . . . . . 2 3. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5. Generic Options . . . . . . . . . . . . . . . . . . . . . . . 3 6. Internationalization and Character Encoding . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 4 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 8.1. URI Scheme Registration . . . . . . . . . . . . . . . . . 5 8.2. Payment Target Type Registry . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . 6 9.2. Informational References . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction This document defines the 'payto' Uniform Resource Identifier (URI) [RFC3986] scheme for designating targets for payments. In its simplest form, a 'payto' URL identifies a payment target type and optionally a target identifier. Additional parameters, such as an amount or a payment reference, can be provided. The interpretation of the target identifier is defined by the payment target type, and typically represents either a bank account or an (unsettled) transaction. 2. Syntax of a 'payto' URL 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" / "creditor-name" / "debitor-name" / "message" / "instruction" authority = path-abempty = pchar = Dold & Grothoff Expires August 1, 2019 [Page 2] Internet-Draft The 'payto' URI scheme January 2019 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 Type 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 method SHOULD accept the options defined in generic-opt. The default operation of applications that invoke a URI with the payto scheme SHOULD 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. 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 payto://sepa/CH9300762011623852957?amount=EUR:200.0&message=hello INVALID (authority missing): payto:sepa/12345 5. Generic Options 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 method. The following options SHOULD be understood by every payment method. amount: The amount to transfer, including currency information if applicable. The format MUST be: amount = [ currency ":" ] unit [ "." fraction ] currency = 1*ALPHA unit = 1*(DIGIT / ",") fraction = 1*(DIGIT / ",") 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. Dold & Grothoff Expires August 1, 2019 [Page 3] Internet-Draft The 'payto' URI scheme January 2019 creditor-name: Name of the entity that is credited (receives the payment). debitor-name: Name of the entity that is debited (makes the payment). 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 method. 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 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. 7. 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 URL. 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. Dold & Grothoff Expires August 1, 2019 [Page 4] Internet-Draft The 'payto' URI scheme January 2019 8. IANA Considerations 8.1. URI Scheme Registration The "payto" URI scheme is to be registered in the "Permanent URI Schemes" registry. Scheme name: payto Status: permanent URI scheme syntax: See Section 2. URI scheme semantics: See Section 3. Applications/protocols that use this scheme name: payto URIs are mainly used by financial software Contact: grothoff@gnu.org Change controller: grothoff@gnu.org References: See References section of this document. 8.2. Payment Target Type Registry This document defines a registry for payment methods. The name of the registry is "Payment Target Type Registry". The registry shall record for each entry: o Name: The name of the payment target type (case insensitive ASCII string) o Description: A description of the payment target type, including the semantics of the path in the URI if applicable. o Contact: The contact information of a person to contact for further information o References: Optionally, references describing the payment method (such as an RFC) and method-specific options The registration policy for this registry is "First Come First Served", as described in [RFC5226]. The registry is initially populated with the following entries: Dold & Grothoff Expires August 1, 2019 [Page 5] Internet-Draft The 'payto' URI scheme January 2019 +---------+-------------------------------+----------+--------------+ | Name | Description | Contact> | References | +---------+-------------------------------+----------+--------------+ | ach | Automated Clearing House. | N/A | [NACHA] | | | The path is a bank account | | | | | number. | | | | sepa | Single European Payment Area. | N/A | [ISO20022] | | | The path is an IBAN. | | | | upi | Unified Payment Interface. | N/A | [UPILinking] | | | The path is an account alias. | | | | bitcoin | Bitcoin protocol. The path is | N/A | [BIP0021] | | | a "bitcoinaddress" as per | | | | | [BIP0021]. | | | | ilp | Interledger protocol. The | N/A | [ILP-ADDR] | | | path is an ILP address as per | | | | | [ILP-ADDR]. | | | +---------+-------------------------------+----------+--------------+ 9. References 9.1. Normative References [ISO20022] International Organization for Standardization, "ISO 20022 Financial Services - Universal financial industry message scheme", May 2013. [NACHA] NACHA, "NACHA Operating Rules & Guidelines", January 2017. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, DOI 10.17487/RFC5226, May 2008, . [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [unicode-tr36] Davis, M., Ed. and M. Suignard, "Unicode Technical Report #36: Unicode Security Considerations", September 2014. Dold & Grothoff Expires August 1, 2019 [Page 6] Internet-Draft The 'payto' URI scheme January 2019 9.2. Informational References [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, . Authors' Addresses Florian Dold Taler Systems SA 7, rue de Mondorf Erpeldange L-5421 LU Email: dold@taler.net Christian Grothoff BFH Hoeheweg 80 Biel/Bienne CH-2501 CH Email: christian.grothoff@bfh.ch Dold & Grothoff Expires August 1, 2019 [Page 7]