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Independent Stream                                               F. Dold
Internet-Draft                                          Taler Systems SA
Intended status: Informational                               C. Grothoff
Expires: October 19, 2019                                            BFH
                                                          April 17, 2019


                  The 'payto' URI scheme for payments
                          draft-dold-payto-06

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
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   This Internet-Draft will expire on October 19, 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
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   described in the Simplified BSD License.





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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
       8.2.1.  ACH Bank Account  . . . . . . . . . . . . . . . . . .   7
       8.2.2.  Business Identifier Code  . . . . . . . . . . . . . .   7
       8.2.3.  International Bank Account Number . . . . . . . . . .   7
       8.2.4.  Unified Payments Interface  . . . . . . . . . . . . .   8
       8.2.5.  Bitcoin Address . . . . . . . . . . . . . . . . . . .   8
       8.2.6.  Interledger Protocol Address  . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informational References  . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   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'
   URL 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.

2.  Syntax of a 'payto' URL

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








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     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 = ALPHA *( ALPHA / DIGIT / "-" / "." )
     path-abempty = <path-abempty, see [RFC3986], Section 3.3>
     pchar = <pchar, see [RFC3986], Appendix A.>


3.  Semantics

   The authority component of a payment URI identifies the payment
   target type.  The payment target types are defined in the "Payment
   Target Types" 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.  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" 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

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

     INVALID (authority missing):  payto:iban/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.





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   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.

   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
   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].





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   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.

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, as well as by interactive
      applications (e.g. email clients, chat applications) that detect
      payto URIs and allow the user to interact with them (e.g. make
      them clickable)

      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 Types".

   The registry shall record for each entry:

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



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

   o  Example: At least one example URI to illustrate the payment target
      type.

   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, or references
      describing the payment system underlying the payment target type.

   The registration policy for this registry is "expert review", as
   described in [RFC5226].  The expert is appointed by the IETF
   Indenpendent Stream Editor.  The expert's review SHOULD consider the
   following criteria:

   1.  The proposed registry entry contains all mandatory information.

   2.  The description clearly defines the syntax and semantics of the
       payment target and optional parameters if applicable.

   3.  Relevant references are provided if they are available.

   4.  The chosen name is appropriate for the payment target type, does
       not conflict with well-known payment systems, and avoids
       potential to confuse users.

   5.  The payment system underlying the payment target type is not
       fundamentally incompatible with the general options (such as
       positive decimal amounts) in this specification.

   6.  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.

   7.  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.

   8.  The payment target and the options do not contain the payment
       sender's account details.






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8.2.1.  ACH Bank Account

   o  Name: ach

   o  Description: Automated Clearing House.  The path consist of two
      components, the routing number and the account number.

   o  Example: payto://ach/122000661/1234

   o  Contact: N/A

   o  References: [NACHA]

8.2.2.  Business Identifier Code

   o  Name: bic

   o  Description: Business Identifier Code.  The path consist of just a
      BIC.  This is used for wire transfers between banks.  The registry
      for BICs is provided by SWIFT.  The path does not allow specifying
      a bank account number.

   o  Example: payto://bic/SOGEDEFFXXX

   o  Contact: N/A

   o  References: [BIC]

8.2.3.  International Bank Account Number

   o  Name: iban

   o  Description: International Bank Account Number (IBAN).  Generally
      the IBAN allows to unambiguously derive the the associated
      Business Identifier Code (BIC).  However, some legacy applications
      process payments to the same IBAN differently based on the
      specified BIC.  Thus the path can either consist of a single
      component (the IBAN) or two components (BIC and IBAN).

   o  Example: payto://iban/DE75512108001245126199
      payto://iban/SOGEDEFFXXX/DE75512108001245126199

   o  Contact: N/A

   o  References: [ISO20022]






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8.2.4.  Unified Payments Interface

   o  Name: upi

   o  Description: Unified Payment Interface.  The path is an account
      alias.  The amount and receiver-name options are mandatory for
      this payment target.

   o  Example: payto://upi/alice@example.com?receiver-
      name=Alice&amount=INR:200

   o  Contact: N/A

   o  References: [UPILinking]

8.2.5.  Bitcoin Address

   o  Name: bitcoin

   o  Description: Bitcoin protocol.  The path is a "bitcoinaddress" as
      per [BIP0021].

   o  Example: payto://bitcoin/12A1MyfXbW6RhdRAZEqofac5jCQQjwEPBu

   o  Contact: N/A

   o  References: [BIP0021]

8.2.6.  Interledger Protocol Address

   o  Name: ilp

   o  Description: Interledger protocol.  The path is an ILP address as
      per [ILP-ADDR].

   o  Example: payto://ilp/g.acme.bob

   o  Contact: N/A

   o  References: [ILP-ADDR]

9.  References

9.1.  Normative References







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   [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,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [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.

9.2.  Informational References

   [BIC]      International Organization for Standardization, "ISO
              9362:2014 Business Identifier Code (BIC)", March 2019,
              <https://www.iso.org/standard/60390.html>.

   [BIP0021]  Schneider, N. and M. Corallo, "Bitcoin Improvement
              Proposal 21", January 2012,
              <https://en.bitcoin.it/wiki/BIP_0021>.

   [HMW12]    Huang, L., Moshchuk, A., Wang, H., Schecter, S., and C.
              Jackson, "Clickjacking: Attacks and Defenses", January
              2012, <https://www.usenix.org/system/files/conference/
              usenixsecurity12/sec12-final39.pdf>.

   [ILP-ADDR]
              Interledger Team, "ILP Addresses - v2.0.0", September
              2018, <https://interledger.org/rfcs/0015-ilp-addresses/>.









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   [UPILinking]
              National Payment Corporation of India, "Unified Payment
              Interface - Common URL Specifications For Deep Linking And
              Proximity Integration", May 2016,
              <http://www.npci.org.in/documents/
              UPILinkingSpecificationsVersion10draft.pdf>.

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


























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