The 'payto' URI scheme for payments
draft-dold-payto-10
Independent Stream F. Dold
Internet-Draft Taler Systems SA
Intended status: Informational C. Grothoff
Expires: June 19, 2020 BFH
December 17, 2019
The 'payto' URI scheme for payments
draft-dold-payto-10
Abstract
This document defines the 'payto' Uniform Resource Identifier (URI)
scheme for designating targets for payments.
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.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Objective . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Syntax of a 'payto' URI . . . . . . . . . . . . . . . . . . . 3
3. Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Generic Options . . . . . . . . . . . . . . . . . . . . . . . 4
6. Internationalization and Character Encoding . . . . . . . . . 5
7. Tracking Payment Target Types . . . . . . . . . . . . . . . . 5
7.1. ACH Bank Account . . . . . . . . . . . . . . . . . . . . 6
7.2. Business Identifier Code . . . . . . . . . . . . . . . . 6
7.3. International Bank Account Number . . . . . . . . . . . . 7
7.4. Unified Payments Interface . . . . . . . . . . . . . . . 7
7.5. Bitcoin Address . . . . . . . . . . . . . . . . . . . . . 7
7.6. Interledger Protocol Address . . . . . . . . . . . . . . 8
7.7. Void Payment Target . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9.1. URI Scheme Registration . . . . . . . . . . . . . . . . . 9
9.2. Payment Target Type Registry . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informational References . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
This document defines the 'payto' Uniform Resource Identifier (URI)
[RFC3986] scheme for designating transfer form data for payments.
1.1. Objective
A 'payto' URI 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.
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1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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 = (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' is defined in [RFC3986] in Section 3.3. 'pchar' is
defined in [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" sub-registry, see Section 9.2. 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.
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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 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).
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.
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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. Tracking Payment Target Types
A registry of Payment Target Types is described in Section 9.2. 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:
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o Name: The name of the payment target type (case insensitive ASCII
string, restricted to alphanumeric characters, dots and dashes)
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 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 six entries as follows (see
also Section 9.2).
7.1. 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], [this.I-D]
7.2. 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], [this.I-D]
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7.3. 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], [this.I-D]
7.4. 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], [this.I-D]
7.5. 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], [this.I-D]
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7.6. 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], [this.I-D]
7.7. Void Payment Target
o Name: void
o Description: The "void" payment target type allows specifying the
parameters of an out-of-band payment (such as cash or other types
of in-person transactions). The path is optional and interpreted
as a comment.
o Example: payto://void/?amount=EUR:10.5
o Contact: N/A
o References: [this.I-D]
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.
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.
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9. IANA Considerations
IANA maintains a registry called the "Uniform Resource Identifier
(URI) Schemes" registry.
9.1. URI Scheme Registration
IANA maintains the "Uniform Resource Identifier (URI) Schemes"
registry that contains an entry for the 'payto' URI scheme. IANA is
requested to update that entry to reference this document when
published as an RFC.
9.2. Payment Target Type Registry
IANA maintains the "Uniform Resource Identifier (URI) Schemes"
registry. IANA is requested to create a new subregistry for payment
methods called the "Payment Target Types" registry.
The subregistry 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)
o Contact: The contact information of a person to contact for
further information
o 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 registration policy for this sub-registry is "First Come First
Served", as described in [RFC8126].
IANA is requested to populate this registry as follows:
Name | Contact | Reference
----------+-------------------------+------------
ach | N/A | [This.I-D]
bic | N/A | [This.I-D]
iban | N/A | [This.I-D]
upi | N/A | [This.I-D]
bitcoin | N/A | [This.I-D]
ilp | N/A | [This.I-D]
void | N/A | [This.I-D]
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10. References
10.1. Normative References
[ISO20022]
International Organization for Standardization, "ISO 20022
Financial Services - Universal financial industry message
scheme", May 2013.
[ISO4217] International Organization for Standardization, "ISO 4217
Currency Codes", August 2018.
[NACHA] NACHA, "NACHA Operating Rules & Guidelines", January 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[unicode-tr36]
Davis, M., Ed. and M. Suignard, "Unicode Technical Report
#36: Unicode Security Considerations", September 2014.
10.2. Informational References
[BIC] International Organization for Standardization, "ISO
9362:2014 Business Identifier Code (BIC)", March 2019,
<https://www.iso.org/standard/60390.html>.
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[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/>.
[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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