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Versions: 00 01 02 04 05 06 07 08                                       
INTERNET-DRAFT                                    Donald E. Eastlake 3rd
Expires August 2001                                        February 2001

         ISO 7812/7816 Numbers and the Domain Name System (DNS)
         --- --------- ------- --- --- ------ ---- ------ -----

                         Donald E. Eastlake 3rd

Status of This Document

   This draft is intended to be become an Informational RFC.
   Distribution of this document is unlimited.  Comments should be sent
   to the author.

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.  Internet-Drafts are
   working documents of the Internet Engineering Task Force (IETF), its
   areas, and its working groups.  Note that other groups may also
   distribute working documents as Internet-Drafts.

   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."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

D. Eastlake 3rd                                                 [Page 1]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS


   There are a variety of servers, web pages, and the like, which
   holders of ISO 7812 financial transaction identification card (i.e.,
   credit/debit card) numbers and ISO 7816 smart card or related numbers
   may need to locate on the Internet. For example, some systems assume
   a smart card holder can contact the issuer of a smart card
   application for maintenance and update functions and the payment
   protocols may assume that a card holder can locate the appropriate
   certification authority to obtain a card holder certificate. This
   document specifies a method using the DNS as an important element in
   locating card related facilities on the Internet by mapping ISO 7812
   and ISO 7816 number systems into domain names.


   The methods proposed herein have not been endorsed by the issuers and
   registries of ISO 7812 and 7816 numbers.


   Suggestions from the following persons, listed in alphabetic order,
   have been incorporated in this document and are gratefully

          Doug Beattie, Electronic Commerce Consultants

          Dave Burdett, Commerce One

          Brian Carpenter, IBM

          Robert Elz, University of Melbourne

          Tony Lewis, VISA International

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INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

Table of Contents

      Status of This Document ...................................1

      Disclaimer ................................................2
      Acknowledgment ............................................2

      Table of Contents..........................................3

      1. Introduction............................................4
      1.1 ISO 7812 Details ......................................4
      1.2 ISO 7816 Details ......................................5
      1.2.1 ISO 7816 '0'-'9' Prefixes ...........................6
      1.2.2 ISO 7816 'A' Prefixes ...............................6
      1.2.3 ISO 7816 'D' Prefixes ...............................6
      1.2.4 ISO 7816 'B', 'C', and 'E' Prefixes .................7
      1.2.5 ISO 7816 'F' Prefixes ...............................7

      2. Inverse Number Mapping and Wildcards....................8

      3. Card Domain Names Specified.............................9
      3.1 ISO 7812 Card Brand, Issuer, and Acquirer Pointers ....9
      3.2 ISO 7812 Acquirer Facilities .........................10
      3.3 ICON Location ........................................10
      3.4 Similar Proprietary Systems ..........................11
      3.5 ISO 7816 Application IDs .............................11
      4. Financial Institutions Not On Line ....................11
      5. ISO 7812 BIN Ambiguity ................................11
      6. Security Considerations ...............................12


      Author's Address..........................................14
      Expiration and File Name .................................14

      Appendix: Initial ISO 7812 Brand Pointers.................15

D. Eastlake 3rd                                                 [Page 3]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

1. Introduction

   Financial transaction cards such as credit and debit cards are
   identified by numbers issued in conjunction with ISO standard 7812
   [ISO 7812-1] and applications that run on ISO smart cards are
   identified by numbers issued in conjunction with ISO standard 7816
   [ISO 7816-5]. In general, the leading digits of such numbers indicate
   the category and/or issuing institution and the remainder of the
   number provides further identification.

   There has been no way, given such a number, to automatically find an
   Internet site related to the card issuer, the card brand, or other
   card facilities.  Some operations in connections with smart card
   resident applications, such as resetting certain error conditions on
   a stored value card, may require contacting the issuer. Other
   protocols may require that other facilities based on card number be
   reached over the Internet.

   A means of automatically mapping such identification numbers into
   domain names means that as soon as a number is known (due to user
   smart card insertion, the reading of a magnetic stripe, or user
   selection from a list of previous entered credit cards, for example),
   the ability would be present to easily attempt to contact facilities
   on the Internet for that number.  Thus web browsers/wallets could
   provide "go to issuer", "go to brand", "get a certificate", etc.,
   buttons whenever an IS0 7812/7816 identification number is known.

1.1 ISO 7812 Details

   Under ISO 7812, card numbers are decimal and the first 6 digits are
   formally known as the Issuer Identification Number or IIN.  This six
   digit prefix is sometimes referred to as the BIN (Bank Identification
   Number), although it applies to more than banks, and the entire
   number is sometimes known as the PAN (Primary Account Number), even
   though these numbers are also used for secondary accounts, Merchant
   accounts, and other account and identification numbers. Card numbers
   are frequently issued in connection with "brands" such as VISA,
   MasterCard, American Express, JCB, Discover, Dinners Club, Air Travel
   Card, etc.

   Formally, ISO 7812 identification card numbers are divided as

D. Eastlake 3rd                                                 [Page 4]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

         1           2-6             7->        last
      | MII | issuer identifier |           |             |
      +-----+-------------------+ account # | check digit |
      | issuer identification # |           |             |
      |         ISO 7812 identification number            |
        MII = Major Industry Identifier as follows
           0 - for ISO/TC 68 and other industry assignments
           1 - airlines
           2 - airlines  and other industry assignments
           3 - travel and entertainment
         4/5 - banking/financial
           6 - merchandizing and banking
           7 - petroleum
           8 - telecommunications and other industry assignments
           9 - for national assignment

   If the number starts with 9, the next three digits are the numeric
   country code as defined in [ISO 3166] and the remainder of the number
   is as defined by that national standards body for that country.

   Account numbers are variable length up to a maximum of 12 digits so
   the maximum total length is 19 bytes.

   The check digit is calculated modulo 10 by the Luhn formula over all
   the preceding digits as specified in [ISO 7812].

   The global registration agency for [ISO 7812] Issuer Identification
   Numbers is the American Bankers Association [ABA] but application for
   an IIN must generally be made through a national standards body.

1.2 ISO 7816 Details

   ISO smart cards have applications on them each identified by a
   hexadecimal Application Identifier (AID) BCD encoded into a maximum
   of 16 bytes.  In the past, most such cards have had a single
   application but multiapplication cards are expected to be more common
   in the future.

   The first hex digit of the AID indicates the type of AID prefix as
   listed below followed by details on each type.  In general, the AID
   prefix is followed a variable length "Proprietary application
   identification extension" (PIX) under the control of the issuer
   identified by the prefix.

D. Eastlake 3rd                                                 [Page 5]

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   0-9  An ISO 7812 IIN.
   A    International registration.
   B-C  Reserved for ISO.
   D    National registration.
   E    Reserved for ISO.
   F    Proprietary non-registered

1.2.1 ISO 7816 '0'-'9' Prefixes

   AIDs with a prefix of '0' through '9' use ISO 7812 IINs for the
   prefix (see section 1.1 above).

      |         ISO 7812        |        | Proprietary application    |
      | issuer identification # |  'FF'  | identifier extension (PIX) |
      |            Application identifier (AID), 2-16 bytes           |

   [ISO 7816] is designed to be independent of IIN length and specifies
   that if the IIN length is odd, it should be padded up the next full
   byte by suffixing a hex 'F' nibble.

1.2.2 ISO 7816 'A' Prefixes

   In AIDs with a prefix of 'A' (i.e., binary 1010), the prefix is
   followed by 36 bits of Registry provider number as 9 BCD digits.
   Values in these 9 nibbles that do not corresponding to a decimal
   digits are reserved for ISO.

      |  Registered Application    | Proprietary application    |
      | provider identifier (RID)  | identifier extension (PIX) |
      |         5 bytes            |       <= 11 bytes          |
      |        Application identifier (AID), 1-16 bytes         |

   The registration authority for RIDs is [TELE DENMARK].

1.2.3 ISO 7816 'D' Prefixes

   The RID consists of the 4 bit D prefix (binary 1101), the country
   code in 12 bits as 3 BCD digits coded according to the numeric

D. Eastlake 3rd                                                 [Page 6]

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   country codes in [ISO 3166], and 24 additional bits as specified by
   the national standards body with BCD coding recommended.

      |  Registered Application    | Proprietary application    |
      | provider identifier (RID)  | identifier extension (PIX) |
      |         5 bytes            |       <= 11 bytes          |
      |        Application identifier (AID), 1-16 bytes         |

1.2.4 ISO 7816 'B', 'C', and 'E' Prefixes

   Prefixes 'B', 'C', and 'E' are reserved for future use by ISO and not
   further specified.

1.2.5 ISO 7816 'F' Prefixes

   Prefix 'F' indicates a proprietary non-registered AID.  Because of
   this, the same 'F' prefixed AID could be used by different
   application providers for different applications.

      |                  Application Label                   |
      | Proprietary application identifier (AID), 1-16 bytes |

D. Eastlake 3rd                                                 [Page 7]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

2. Inverse Number Mapping and Wildcards

   When numbers are allocated in lexically hierarchical blocks so that a
   prefix or suffix of digits is a meaningful division, the DNS wildcard
   feature can be used to provide a convenient delegation and lookup
   mechanism.  This works even when the numbers and prefixes/suffixes
   are variable length. In this regard, it is important to remember that
   more specific names override less specific ones for DNS wildcards.

   Domain names start with the most significant label on the right and
   go to less significant labels as you go left while in ISO 7812 and
   7816 numbers the leading or left most digits are the most significant
   while the trailing or right most digits are less significant.  Thus,
   the digits must be reversed to match the card number and DNS naming
   systems and the digits must be interspersed with dots to provide
   hierarchical division into DNS domains.

   Note that the transformed, reversed number need not be exposed to
   users but could be generated internally by software in an automatic

   [Note: while card.reg.int was assigned by IANA for this purpose,
   follwing the 10 May 2000 statement by the IAB, this may be changed to
   card.arpa or some other *.arpa.]

   For example, currently the American Express card brand is the only
   one using [ISO 7812] numbers starting with 37.  However, this is not
   a guarantee for all time and it could be that at some point some BIN
   numbers starting with 37 would be assigned to a different brand. If
   you are looking up facility "z" for card number 37012345678 (not a
   valid American Express number), you could do a retrieval with a name
   like based on the first six digits of the
   number. A wild card RR with the name *.7.3.z.card.reg.int would match
   this and would appear in the response with its name expanded to the
   specific name asked for, but only if there were no more specific
   name.  If there were a specific name, for
   instance, it would always be chosen in preference to the
   *.7.3.card.reg.int wildcard in this case because it is a more exact
   match. Thus more specific values can punch out holes in ranges
   established by shorter, less specific prefixes.  On the other hand,
   if a retrieval were done for, it would get
   the more general *.7.3.z.card.reg.int wild card since it does not
   match the more exact wildcard.  (The situation is generally a little
   more complex than indicted here because additional intermediate
   length wildcards may be needed.  See the Appendix for a more complete
   example zone.)

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3. Card Domain Names Specified

   Subdomains are currently defined within the card.reg.int domain as
   follows in alphabetic order:

   [Note: while card.reg.int was assigned by IANA for this purpose,
   follwing the 10 May 2000 statement by the IAB, this may be changed to
   card.arpa or some other *.arpa.]

      acquirer.card.reg.int - ISO 7812 card acquirers
      aid.card.reg.int      - ISO 7816 application identifiers
      brand.card.reg.int.   - ISO 7812 card brands.
      issuer.card.reg.int.  - ISO 7812 card issuers.

   To find a facility, you need to (1) get the number, (2) reverse the
   order of these digits, and (3) put a dot between each digit and add
   the appropriate facility suffix.  [ISO 7812] financial transaction
   card identification numbers generally must be truncated to six digits
   if revealing the full number in the DNS queries would be a security
   problem.  Generally revealing the entire number in a DNS query is not
   a problem for [ISO 7816] AIDs.

   None of the facility pointers obtained via these means need be
   exclusive and these card related Internet facilities may have other
   names and URLs that will also work.  These facilities are intended to
   supplement, not necessarily replace, direct communication of domain
   names and URLs from financial institutions to their customers.

3.1 ISO 7812 Card Brand, Issuer, and Acquirer Pointers

   The card brand and issuer home pages would be located by creating the
   numeric portion as above and appending ".brand.card.reg.int" or
   ".issuer.card.reg.int" respectively.  A CNAME RR will be stored at
   that name pointing to the actual domain name for the home page.  A
   CNAME is chosen, rather than having specific "A" RRs pointing to
   host(s), "MX" RRs pointing to mail servers, etc., to minimize the
   update load on the card.reg.int sub-domains.  Changes in the serving
   host, mail servers, etc., need only be made under the facility's
   domain name, which the CNAME points to, rather than also under

   For example, the brand for the card 551204..., a MasterCard card,
   would be found by browsing at and the
   issuer for the card 471922..., a VISA card, would be found by
   browsing at  These domain names can
   be automatically generated from a card number and need not be exposed
   to users.

D. Eastlake 3rd                                                 [Page 9]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

   The Appendix shows possible initial content of the brand.card.reg.int
   domain.  There are relatively few brands and they are allocated to
   moderately compact blocks of numbers with relatively few exceptions
   not belonging to the block brand. So there will probably be under
   2,000 entries in the brand.card.reg.int subdomain.

   Since there are only a few tens of thousands of banks and other
   issuers of significance in the world for financial transaction cards,
   there should be well under 200,000 entries in the issuer.card.reg.int

   Although at this time very large blocks of numbers are generally
   allocated to brands (for example almost all card numbers starting
   with 5 and 4 are MasterCard and Visa cards, respectively), some
   numbers within these large blocks may be carved out by more specific
   entries for other brands.

3.2 ISO 7812 Acquirer Facilities

   Generally, merchants are assigned merchant IDs from the space of PANs
   by their acquirer.  Acquirer facilities can be located from such
   numbers using the .acquirer.card.reg.int suffix.

3.3 ICON Location

   For many of the facilities locatable via card.reg.int, some user
   interface software will want to be able to display an image or icon.
   Standard suffixes to the computed domain name of the facility are
   recommended, as listed below, to make the default location of such
   icons easier.

       Suffix to Domain Name            Image Size in Pixels

      /icons/exsmall.gif                32 x 32  or  32 x 20
      /icons/small.gif                  53 x 33
      /icons/medium.gif                103 x 65
      /icons/large.gif                 180 x 114
      /icons/exlarge.gif               263 x 166

   The larger dimension above is horizontal and the smaller is vertical.
   The extra small version is permitted to be a 32x32 square which is a
   common desk top operating system icon size.  It is recommended that
   displaying the extra small size be avoided due to lower
   recognizability is such small images.  The color palette of the icons
   should be limited to colors typically available in an 8 bit or 256
   color environment.

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INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

   The above file name, size, and color recommendations are similar to
   those in Book 2 of the SET standards [SET].

3.4 Similar Proprietary Systems

   Some proprietary systems use numbers schemes similar to [ISO 7812] or
   [ISO 7816].  For instance, an "Example" stored cash card system might
   use card IDs that have the same structure and prefixes as [ISO 7812]
   card numbers.  Such schemes are welcome to use the techniques
   described in this document for inverse look up via DNS but should
   place the inverse tree under their proprietary domain name.  For
   instance, the hypothetical stored cash card system could use

3.5 ISO 7816 Application IDs

   Facilities based on [ISO 7816] application identifiers can be found
   using the

   suffix.  While a subset of such IDs are structured like ISO 7812
   PANs, nevertheless, they are likely to need different facilities so
   no reference is made to the parts of the card.reg.int DNS tree
   allocated for non-smart card use.

4. Financial Institutions Not On Line

   Some numbers may be allocated to institutions that do not have a
   network presence. In some of those cases, a wildcard could provide an
   appropriate pointer, say to a brand supplied bank lookup page that
   provides telephone number and address or the like to contact the
   bank.  However, in cases where the next higher level wildcard would
   provide inappropriate pointers for such institutions, it will be
   necessary to add entries for such numbers which are CNAMEed to "not-
   on-line.card.reg.int" which will not exist.  Thus an appropriate
   error message will be generated.

5. ISO 7812 BIN Ambiguity

   For the facilities under card.reg.int using ISO 7812 numbers, the BIN
   is defined as the first six digits of the account number.  In many
   cases an issuer or certification authority is defined by fewer

D. Eastlake 3rd                                                [Page 11]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

   digits, for example the first four digits.  This is no problem as a
   wild card can be used to match all extensions of this shorter prefix.
   However, cases where six digits are insufficient need special
   handling as describe below.  Such situations can arise due to
   subdivision / subdelegation of a BIN for administrative reasons, due
   to sale of part of a card population, as parts of bank mergers and
   splits, etc.  Additional digits can not be used in the DNS query
   because they would reveal too much of the card number and thus be a
   security risk.

   If multiple institutions have decided to share a BIN, there are
   several ways the situation can be handled.  For the issuer web page
   either (1) the institutions sharing the BIN can run a common web page
   with links to their individual pages on it or (2) if they are all the
   same brand, the brand can run such a multi-issuer referral page at
   the BIN or, in many cases, at a higher level wildcard or (3) in the
   event that they are different brands, the card.reg.int maintainer can
   run a page providing access to the different sub-BIN issuers.  A
   multiple issuer home page could just have names, icons, and links to
   the separate institutions or more complex indexing or search
   facilities if it covered many banks.  While this problem in not
   expected to arise for the brand.card.reg.int subdomain, similar
   solutions apply if it does.

6. Security Considerations

   This document concerns a means to map ISO 7812 financial card and ISO
   7816 smart card application identification numbers into the Domain
   Name System (DNS) so that card related facilities on the Internet can
   be automatically located.  The security of the resulting pointers is
   dependent on the integrity of the maintainer of the domain used for
   this purpose and the security of the DNS, including the use of
   security extensions [RFC 2535].  However, note that when used in
   connection with many smart card application, certificate issuance,
   and payment schemes, the security mechanisms of the protocols used
   after communications is established provide strong protection against
   spoofing or compromise of sensitive information even if the DNS were

   For currently existing types of ISO 7812 financial numbers, care
   should be taken in making DNS queries that an entire sensitive
   identification number is NOT used.  Since DNS queries are not
   encrypted, this would expose the card number within the Internet. No
   more than the initial six digits may be used.  (These consideration
   do not generally apply to numbers based on ISO 7816 application

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INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS


   [ABA] - <http://www.aba.com>
            American Bankers Association
            1120 Connecticut Avenue, N.W.
            Washington, DC 20036 USA


   [ISO 3166] - Codes for the representation of names of countries.

   [ISO 7812-1] - Identification card - Identification of Issuers.

   [ISO 7816-5] - Identification card - Integrated circuit(s) cards with
   contacts - Numbering system and registration procedures of
   application identifiers

      Note: The International Standards Organization web site is at
      <http://www.iso.ch>.  Final ISO standards, such as 3166, 7812, and
      7816, are not generally available on the Internet and usually must
      be purchased through national standards bodies.

   [RFC 1034] - Domain Names - Concepts and Facilities, P. Mockapetris,
   November 1987

   [RFC 1035] - Domain Names - Implementation and Specifications, P.
   Mockapetris, November 1987.

   [RFC 2535] - Domain Name System Security Extensions, D. Eastlake,
   March 1999.

   [SET] - Secure Electronic Transaction (SET) Specification, Version
   1.0, May 31, 1997, available from <http://www.setco.org>.
        Book 1: Business Description
        Book 2: Programmer's Guide
        Book 3: Formal Protocol Definition

   [SET-EIG] - External Interface Guide to SET Secure Electronic
   Transaction, September 24, 1997, available from

   [TELE DENMARK] - <http://www.teledanmark.dk>,
            Tele Denmark
            Attn: ISO/IEC 7816-5 Registration Authority
            Teglholmsgade 1
            1790 Copenhagen V

D. Eastlake 3rd                                                [Page 13]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

Author's Address

   Donald E. Eastlake 3rd
   155 Beaver Street
   Milford, MA 01757 USA

   Telephone:   +1 508-634-2066 (h)
                +1 508-261-5434 (w)
   FAX:         +1 508-261-4447 (w)
   EMail:       Donald.Eastlake@motorola.com

Expiration and File Name

   This draft expires August 2001.

   Its file name is draft-eastlake-card-map-08.txt.

D. Eastlake 3rd                                                [Page 14]

INTERNET-DRAFT                         ISO 7812/7816 Numbers and the DNS

Appendix: Initial ISO 7812 Brand Pointers

   This table shows possible initial brand name pointers that might be
   installed in the brand.card.reg.int domain.

   [In light of the 10 May 2000 IAB statement on infrastructure domains,
   card.reg.int may be changed to card.arpa or other *.arpa.]

         Initial Name                  CNAME

           *.brand.card.reg.int      unknown-brand.card.reg.int
         *.1.brand.card.reg.int      www.air-travel-card.com
         *.3.brand.card.reg.int      unknown-brand.card.reg.int
       *.0.3.brand.card.reg.int      www.dinersclub.com
     *.6.0.3.brand.card.reg.int      www.dinersclub.com
   *.      www.jcb.co.jp
     *.8.0.3.brand.card.reg.int      www.dinersclub.com
   *.      www.jcb.co.jp
       *.1.3.brand.card.reg.int      www.jcb.co.jp
       *.3.3.brand.card.reg.int      www.americanexpress.com
     *.3.3.3.brand.card.reg.int      www.americanexpress.com
   *.      www.jcb.co.jp
       *.5.3.brand.card.reg.int      unknown-brand.card.reg.int
     *.2.5.3.brand.card.reg.int      unknown-brand.card.reg.int
   *.      www.jcb.co.jp
       *.6.3.brand.card.reg.int      www.dinersclub.com
       *.7.3.brand.card.reg.int      www.americanexpress.com
       *.8.3.brand.card.reg.int      www.dinersclub.com
         *.4.brand.card.reg.int      www.visa.com
         *.5.brand.card.reg.int      www.mastercard.com
         *.6.brand.card.reg.int      unknown-brand.card.reg.int
       *.0.6.brand.card.reg.int      unknown-brand.card.reg.int
     *.1.0.6.brand.card.reg.int      unknown-brand.card.reg.int
   *.      www.novus.com

   (MasterCard actually only has numbers starting with 51 through 56 but
   until some other brand with cards issued with ISO 7812 numbers
   starting with a 5 are entered into the DNS zone, there is no reason
   to go to any more detail in the wildcard.)

D. Eastlake 3rd                                                [Page 15]