EMV — Banking and Retail
NBX —- LINK Application Interface Specification (AIS)
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RoLe Name AREA OF I SIGNATURE Date
RESPONSIBILITY
Authors Rex Dixon on behalf I Business
of Post Office Ltd Architecture
Product
Deployment
Technical
Architecture
DA Sign-off David Gray Design
(Peer Reviewer) Authority
Programme Beverley Dunn Project
Director Delivery
Fujitsu Gill Jackson
Services Sign-
off
NBX - LINK Application Project:
Interface Specification (AIS) Doc Ref:
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FU,
EMV — Banking and Retail
NB/IFS/024
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1 Document Control
1.1 Document Information
Horizon Release No: S80R
Document Title:
EMV Banking and Retail: NBX — LINK Application Interface Specification
Document Type:
Application Interface Specification
Abstract: This document details the application interface between the Horizon
domain and LINK, including ICC
Document Status: Approved
Originator & David Gray
Department:
Design Authority
Contributors:
Post Office
Distribution:
Design Authority - David Gray
POL Document Control — Post Office Programme Office
LINK — Geoff Barker
Fujitsu Services: Gill Jackson
N/A
Supplier Distribution:
Client Distribution:
Table 1: Document Information
1.2 Document History
Version I Date Reason for Issue Associated
WP /CT
0.1 19 Nov 2003 I First working draft. Based on document produced by IBM
entitled “Network Banking Engine: NBE —- LINK
Application Interface Specification (AlS)” version 3.0, and
including ICC support
0.2 3 Dec 2003 Updated to reflect version 4.0 of “Network Banking
Engine: NBE —- LINK Application Interface Specification
(AIS)’, also minor changes following discussions
0.3 12 Dec 2003 I Updated following joint review on 9/12/03
0.4 20 Jan 2004 Updated following review comments from POL
0.5 26 Jan 2004 — Updated following joint review on 22/01/04
1.0 9 Feb 2004 Updated following joint review on 5/02/04
1.4 7 Apr 2004 Updated following series of minor clarifications
1.2 13 May 2004 I Updated following series of minor clarifications
2.0 13 Aug 2004 I Updated following joint review on 14/05/04 and
subsequent emails
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NB/IFS/024
24 26 May 2005
2.2 3 Aug 2005
$75
result of re-accreditation testing
Updated for CT 363 and for minor corrections discovered I CT 363 /
during testing prior to initial release at Horizon release CP 3997
Updated as a result of comments received, and as a
3.0 15 Aug 2005
Issued for Sign-off
Table 2: Document History
1.3 Change Process
Any changes to this issued version of tI
Tony.W.Stevensmailto?
1.4 Review Details
Review
Comments by :
Comments to :
Review Rex Dixon, Fujitsu Services
this document will be made, controlled and distributed by: -
Mandatory Review Authority Name
Post Office Ltd
Beverley Dunn, David Gray
Fujitsu Services Ltd
Analysis & Solution Specification Allan Hodgkinson
DU Design Authority
Andy Kennedy
DU Design Team Designer Rex Dixon
Test Design
Peter J. Robinson
LINK
Michael Abendstern
Optional Review / Issued for Information
Post Office Ltd
Bob Booth, Seamus Scullion, Jason Crellin
Fujitsu Services Ltd
Release Manager
Bill Reynolds
DU Design
Mark Jarosz, Nasser Siddiqi, Alex Robinson
DU Development Team Leader Peter Ambrose
LINK
1.5 Changes in this Version
Version Changes
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3.0 Gill Jackson added as signatory for Fujitsu Services
2.2 Section 4.1.2 — Amount, Transaction (bitmap ref. 004): removed reference to EUR cents.
Section 4.1.2 — Authorisation Data (bitmap ref. 123): Sub-Field 14 removed as it only
applies to PIN changes, which are not supported.
Section 4.1.2 — Data, Expiration (bitmap ref.014): added clarification “This will only be
for deposits”.
Section 4.1.2 - Message Security Code (bitmap ref. 096): format corrected from “an” to
“ans”.
Section 4.1.2 - Point of Service Data (bitmap ref. 061), subfield 9 (Cardholder
authentication entity): added value 0 (Not authenticated) if not PIN (i.e. for a deposit).
Section 4.1.2 — Point of Service Data (bitmap ref. 061), subfield 12 (PIN capture
capability): added value 0 if no PIN entry capability (i.e. for a deposit).
Section 4.1.2 - Track 2 Data (bitmap ref. 035): added condition that it will not be present
where card details have been manually entered.
24 Section 1.1 —- Horizon Release updated to S80R.
Section 1.7 - Updated to LISS 2005-1.
Sections 4.1.2, 4.2.1.2, 4.2.2.2, 4.2.3.2, 4.2.4.2, 4.2.5.2 and 4.2.6.2 — Application PAN
Sequence Number (bitmap ref. 023): clarified that it is required for manually entered
transactions only when the card's issue number has been captured. [FS Peak 110188,
110679]
Sections 4.1.2 and 4.2.1.2 — Authorisation Data (bitmap ref 123): removed from 0100
message. [POL Incident 1153; FS Peak 108959]
Section 4.1.2 — Point of Service Data (bitmap ref. 061), subfield 2 (Cardholder
authentication capability): added value 0 (No electronic authentication) for deposits.
[LINK MTPR 0292, 0295; POL Incident 1212; FS Peak 110150]
Section 4.1.2 - Point of Service Data (bitmap ref. 061), subfield 3 (Card capture
capability): changed to 0 (no capture) from 1 (capture). [LINK MTPR 0275; POL Incident
1159; FS Peak 108967]
Section 4.2 — Corrected description of which bitmaps appear in the definitions.
Section 4.2.4.2 (Balance Enquiry Response) — Clarified that, for a decline, the length of
this field must be set to ‘000’. [POL Incident 1196]
Section 4.2.7.2 (Reversal Request) — Added a note that NBX does not include any of the
Optional fields.
Table 3: Changes in this Version
1.6 Key Contacts
Name I Position Phone Number
Jason Crellin Solutions Architect
Michael Abendstern Technical Specialist
Table 4: Key Contacts
1.7 Associated Documents
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Reference Version I Date Title Source
LISS 2005-1 LINK Switch Service Interchange LINK
Vsn 1.0 Standard — LINK Card Scheme Service
2004-1 LINK Reconciliation File Specification LINK
Vsn 1.0 (LREC) Standard Formats
SU/PLA/O16 I 0.3 NB Volume Model Comparisons Post Office
NB/IFS/028 NBX — LINK Technical Interface Post Office
Specification
NB/IFS/033 Horizon — LINK Mapping Post Office
2005-1 LINK Switch Service Interchange LINK
Vsn 1.0 Standard — LINK Deposits Service
Vsn 5.6 I Jan LINK Switch Service Interchange LINK
2002 Standard (LISS Security Standard)
Table 5: Associated Documents
Unless a specific version is referred to above, reference should be made to the current approved versions
of the documents.
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Table of Contents
1 DOCUMENT CONTROL 2
441 Document Information 2
1.2 Document History 2
1.3 Change Process 3
14 Review Details 3
1.5 Changes in this Version 4
1.6 Key Contacts 4
17 Associated Documents 5
2 INTRODUCTION 8
24 Scope 8
2.2 Structure 8
23 Terms and Abbreviations 8
3 OVERVIEW OF THE INTERFACE 9
3.1 Data Description 9
3.2 Derivation and Use of Data 11
3.3 Non Computer Data 13
3.4 Clarifications to LINK Standard 13
4 DATAITEMS 14
44 Data Item List 14
4.14.1 General Message Element Definitions and Abbreviations 14
4.1.2 Messages Data Elements 15
4.2 Data Interpretations 25
4.2.1 [R3] - Balance Enquiry 26
4.2.2 [R3] - Financial Transaction Request - Withdrawal 27
4.2.3 [R3] - Financial Transaction Request - Deposit 29
4.2.4 [A1] - Balance Enquiry Response 31
4.2.5 {A1] - Financial Transaction Request Response - Withdrawal 32
426 [A1] - Financial Transaction Request Response - Deposit 33
4.2.7 [E1] - Reversal Request 34
4.2.8 [E2] - Reversal Request Response 36
4.2.9 Administration Advice (0620) 37
4.2.10 Network Management Messages (0800 / 0810) 38
4.2.11 LREC — Reconciliation File 39
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5 TRANSFER STRUCTURE 40
5.1 Transfer Grouping 40
5.2 Transfer Structure 40
5.3 Record Structure 41
54 Sequences 41
5.5 Data Volumes 41
5.6 Data Authentication 41
5.7 Data Dictionary 41
6 SECURITY OF TRANSMITTED DATA 42
6.1 Protected Data 42
6.2 Encryption and Decryption Methods 42
6.3 Session Establishment 42
64 Key Management 42
7 OPERATIONAL PROCEDURES 44
74 Processing Cycles 44
7.2 Transfer Initiation 44
7.3 Security Procedures 44
74 Fallback Procedures 44
75 Downgrade Transactions 44
7.6 Control 45
8 APPENDIXA 46
84 Response Codes and Reversal Codes 46
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2 Introduction
The purpose of this document is:
* To specify the interface between the NBX and LINK systems using LIS5.
e To provide the development teams with sufficient detail to develop the NBX - LINK interface.
« To provide a consistent communications vehicle amongst the development teams that have
responsibility for developing the various components comprising the application.
2.1 Scope
This document applies to the interface between the NBX and LINK only. It includes only those financial
transaction messages, network messages, reconciliation and settlement messages sufficient to support the
financial services being delivered by Post Office Limited via the LINK systems.
2.2 Structure
This AlS document follows Post Office Limited’s AIS standard.
Section 3 contains a high level overview of the NBX — LINK interface and its context.
Section 4 contains a detailed description of the messages to be exchanged, and the derivation and use of the
exchanged data items. All data items exchanged are specified in LISS.
Section 5 contains details of the data transfer.
Section 6 contains details of security of the exchanged data items. This section identifies the security needed
for each data item (e.g. encryption) and details of the method to be used.
Section 7 contains any relevant details of operational procedures relating to the interface.
2.3 Terms and Abbreviations
Not used
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3 Overview of the Interface
3.1 Data Description
The following messages are exchanged over the NBX - LINK interface:
NBX Description Direction
Message Id
[R3] Authorisation / Financial Transaction Request: NBX > LINK
e balance enquiry (0100)
e withdrawal (0200)
e deposit (0200)
Note: there is no separate message to LINK for
withdrawal with balance. LINK will always return
the balance to NBX if sent by the issuer.
[A1] Authorisation/Financial Transaction Request LINK > NBX
Response:
* balance enquiry response (0110)
e withdrawal response (0210)
e deposit response (0210)
Each of the above will have a response code
that indicates approve or decline with reason
and any required action (e.g. card retention).
[E1] Reversal Request: NBX > LINK
* reversal (0420)
*° reversal repeat (0421)
Please note that the number of times the 0421
message is sent is configurable within the NBX,
up to a maximum of 9,999 times.
[E2] Reversal Request Response Message (0430) LINK > NBX
0620 Administration Advice (0620) NBX -> LINK
Administration advice messages (0620) are sent I LINK > NBX
to/from LINK in order to initiate investigation of
a problem by either LINK or the NBX
0800 Network Management Request (0800): LINK > NBX
Echo test (handshake)
Logon / Logoff NBX
End of Day (cutover)
Security Key Change
Key Change Request
Online Key Verification
-> LINK
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0810 Network Management Request Response NBX > LINK
(0810)
LINK > NBX
LREC Reconciliation File LINK -> NBX
(The Report/Standard file format will be used for
the LREC file (Ref. [2]. The file transfer
mechanism and conditions of transfer are
described in the NBX — LINK Technical Interface
Specification (Ref. [4]).
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3.2 Derivation and Use of Data
The messages listed above are generally exchanged as a result of a transaction initiated either by a clerk at a
Post Office outlet or by LINK. The NBX acts as a message router, filtering messages based on business rules
and transforming received messages into the appropriate format for forwarding to the next system in the
message sequence.
The following table shows the derivation and use of each message exchanged between the NBX and LINK in
terms of the received message that causes each NBX - LINK message to be exchanged, and the transmitted
message resulting from the NBX - LINK message exchange:
Message Sequence
Horizon Horizon NBX LINK
Outlet Campus
[Ri] > [R2] > 0100/0200
[R3]>
< [A3] < [A2] =
0110/0210
{A1]
[Co] > [C2] > 0420/0424
[E1]>
< 0430
{E2]
The messages exchanged over this interface relating to end of day, reconciliation and settlement are initiated
by LINK, and are neither derived from received messages nor used to generate onward messages.
Security key exchange messages are initiated by LINK or NBX and acknowledged by the other party. Either
LINK may send a new AWK or NBX may request that LINK sends a new AWK. After a Logon initiated by
either party LINK will send a new AWK. The connection type is Acquirer only. The following table shows the
derivation and use of each security message exchanged between LINK and the NBX. See Ref. [7].
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Message Sequence
Horizon Horizon NBX LINK
Outlet Campus
e 0800 (Logon
061)
0810 =
< 0800 (Key
Change -
Acquirer zone
code 161)
0810 >
0800 (Logon >
071)
< 0810
Fe 0800 (Key
Change -
Acquirer zone
code 161)
0810 >
< 0800 (Key
Change -
Acquirer zone
code 161)
0810 >
0800 (Key is
Change
Request -
Acquirer
zone 181)
< 0810
< 0800 (Key
Change -
Acquirer zone
code 161)
0810 >
ee 0800 (Online
Key
Verification
Acquirer ZMK
code 199)
0810 >
Other 0800 messages may be initiated by either LINK or NBX (with the exception of the End of Day message,
which is LINK initiated), and are acknowledged by a 0810 response from the other side.
The use of Handshakes is described in the NBX — LINK Technical Interface Specification (Ref. [4]).
All 0100 and 0200 messages sent out by NBX prior to sending the 0810 approved key change will have used
the current AWK to encrypt the PIN Block. As soon as the 0810 approved response is transmitted, the new
AWK becomes active so that all messages generated after its receipt use the new AWK to encrypt the PIN
Block.
In the event that the Key Check Value received by NBX (with the AWK in the 0800 Key Change message)
does not match the one created when testing the new AWK, NBX will return a 0810 denied response. Under
these circumstances the new AWK will NOT be implemented and any subsequent transactions will continue to
have the PIN Block encrypted using the current AWK.
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When a new AWK is sent, LINK sets a timer flag which inhibits further key exchanges. This flag is unset
enabling further key exchanges, after a configurable period (currently 2 minutes), if a key exchange is not
received.
3.3 Non Computer Data
All data being transported across this interface is originated/received from a connected computer system or
from reference data (supplied by the Post Office Limited RDS or held internally within the NBX).
3.4 Clarifications to LINK Standard
Point of Service Condition Code (Bitmap Reference 025) will initially be set to value 54 (Non ICC Capable
Branch ATM). Value 55 will be used to indicate ICC Capable Branch ATM when chip read support added.
Transaction Amounts are likely to contain pence - they will not be rounded to whole pounds or ten’s of
pounds.
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4 Data Items
4.1 Data Item List
4.1.1. General Message Element Definitions and Abbreviations
The following section summarises the list of LINK Message Elements for each group of transactions, together
with which message(s) they are present in. Each message is classified and identified using the RAC (Request
/ Authorise / Confirm) model. Each message element references the corresponding ISO 8583 bitmap position.
The ISO 8583 bit map reference has been included for ease of reference.
The abbreviations used to describe the format of each data element (DE) and Data Sub-elements are shown
in the following table (taken from the LINK Switch Service Interchange Standard (LISS), (Ref. [1]):
Notation IExplanation
a Alphabetic characters only (upper case)
n Numeric Digits only
Is Special characters
lan Alphabetic (upper case) or Numeric characters
as Alphabetic (upper case) or Special characters
ns Numeric or Special characters
ans, (Alphabetic (upper case), Numeric or Special characters only
DD Day
MM Month
YY Year
hh Hour
mm Minutes
[ss [Seconds
LL Length of variable field that follows represented using two characters
LLL Length of variable field that follows represented using three characters.
VAR Variable length field
3 Fixed length field (e.g. 3 characters in this example)
10 Variable length field (e.g. up to a maximum of 10 characters in this example). LL or
LLL to indicate the actual length of the field will prefix all variable length fields.
h hexadecimal representation of the data
iz tracks 2 and 3 data as defined by ISO 7811 and ISO 7813
The Field Size column gives the number of characters (octets) required for the data item, as shown in the
table below.
Abbreviation I Description
3 Fixed Length field. Numeric fixed length fields are right justified and zero
padded. Fixed length string fields are left justified and space padded.
10 Variable length field (up to a maximum of 10 characters in this example).
Notes:
e Fixed length numeric fields are unpacked, right justified and zero filled.
e Fixed length alphanumeric fields are left justified and space filled.
The “Required” column indicates whether the field is Mandatory or Conditional for the messages defined in this
AIS. For conditional fields, the field description should indicate under what circumstances the data for the field
should be populated or omitted from the message.
The “Description” column contains a brief description of the field, as used in the messages defined in this AIS
together with any additional comments.
The LINK and NBX Servers both use the ASCII English character set (CCSID = 437).
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4.1.2. Messages Data Elements
The LISS Data Elements exchanged within messages over this interface are listed below. A fuller description is given in the LINK Switch Service
Interchange Standard (LIS5), (Ref. [1]). The ICC data elements are represented from the 3° bitmap on this interface.
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A greyed out row in the following tables means that the field is not required and may not be populated in messages from NBX to LINK. The NBX will log
any such fields received from LINK but will not process them further.
LISS Data Element Bitmap] Format I Field I Source IDescription Required
Ref. Si
: IR3] I (R3] I At] I tat] I (€1) I 2) I 0620 I 0800 I o810
0100 I 0200 I 0110 I 0210 I 0420 I 0430
10424
[Account Identification 1 102 I ans 28 I Issuer INBX does not pass Account Identification 1 field to the mu [uM I[o
LUVAR counter systems
[Acquiring Institution 019 n 3 Not appropriate to messages passed on this interface
ICountry Code
[Acquiring Institution 032 n 11 I NBX from ICode identifying the Acquirer (Post Office Limited). Set to mM ]mM]mM {mM {mM [oo
Identification Code LLVAR Ref Data I2200040000 preceded by a length indicator of 10.
Additional Amounts 054 I an I. 120 Bank Identifies account balance value (included by LINK if Mfc
LULVAR provided by bank)
[Additional Response Data I 044 I ans 25 I Bank INot appropriate to messages passed on this interface.
LLVAR
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IAdvice / Reversal Reason
Code
060
an
LLLVAR
NBX
Required for advice, reversal and ICC transactions.
lUsed in request messages from ICC capable terminals to
indicate Status of Last Chip Read attempted and to provide
ICryptogram Information Data
Magnetic stripe cards
Reversal Requests (0420/0421 messages):
Bytes 1-2 are set to 80
Bytes 3-4 give a reason for the reversal
Remaining bytes are not transmitted
ICC cards
[3] Requests (0100/0200 messages)
Bytes1-2 are set to 30
Byte 3 is Status of Last Chip Attempt
Bytes 4-5 is Cryptogram Information Data
Fallback [R3] Requests (0100/0200 messages)
Bytes1-2 are set to 30
Byte 3 is Status of Last Chip Attempt (value 2)
Bytes 4-5 is Cryptogram Information Data (value
C0)
Reversal Requests (0420/0421 messages)
Bytes 1-2 are set to BO
Bytes 3-4 give a reason for the reversal
Byte 5 is Status of Last Chip Attempt
Bytes 6-7 is Cryptogram Information Data
See Appendix A for Reversal Reasons
Amount, Cardholder Billing
12
Not appropriate to messages passed on this interface —
Horeign currency transactions are not supported by NBX.
Amount, Transaction
Clerk at
Outlet
Decimal amount in smallest unit of the specified currency
(e.g. GBP pence)
Not required for balance enquiry
Amount, Transaction Fee
028
an
Post Office Limited will not apply Acquirer charges (format
Jannnnnnnn)
Amount, Transaction
Processing Fee
030
an
Bank
Issuer charge. This field will not be returned by LINK in a
LINK denied transaction (format annnnnnnn).
Application Interchange
Profile (AIP)
138
icc
From ICC, indicating capability to support specific functions
in application
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[Application PAN Sequence
Number
023
Clerk at
Outlet
Identifies and differentiates cards with the same PAN
Required for ICC transactions, or if the card’s issue number
has been manually entered,
Acquirer decision as to whether sent in the reversal message
(0420/0421) — copied from original transaction. Required in
10430 if present in 0420/0421
Application Transaction
Counter (ATC)
137
lec
1A sequence number (counter) calculated by the ICC and
passed to the terminal application.
lAcquirer decision as to whether sent in the reversal message
(0420/21) - copied from original transaction. Required in
10430 if present in 0420/0421
Authorisation Data
123
ans
LLLVAR
255
Clerk at
Outlet
[Sub-Fields 1-15, 16 do not apply.
[Sub-Field 17 contains number and value of cheque deposit if
applicable. Number of cheques will be set by NBX to 001
Format of sub field 17 is: n 15
Position 1-3 Number of cheques (001 for NBX)
Position 4-15 Value of cheques (in the smallest unit of
transaction currency)
[Sub-Field 18 Bilateral Discretionary Data must contain Start
Date of card where one exists and the card details have been
manually entered
Format of Sub-Field 18 is: ans ..99
Authorisation Identification
Response
038
an
Not required for NBX transactions - POS Transactions Only
IAuthorisation Response
Data
121
ans
LLLVAR
abe
Not required for NBX transactions - used for Cheque
Clearance Date.
This could be retumed by an issuer to state when cheque
funds will clear. NBX must be able to accept this, but will log
lonly.
lAuthorising Agent
Institution Id Code
113
n
LLLVAR
Bank
Institution approving or declining the transaction
Bit Map Secondary
h
NBX from
system
Indicates presence of data elements in a message in range
1065 to 128. This data element may be omitted if no elements
in range 065 to 128 are contained in message
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Bit Map Tertiary 065 I oh 16 I NBX from IRequired for ICC based transactions (i.e. data elements in I
system range 129 to 192)
ICard Acceptor Identification} 042 I ans 15 I NBX from INBX will populate with the Post Office Short Name (see Ref.
Code system I[5] from Reference Data, left justified and space filled
First 40 characters of outlet address in format
Icard Acceptor Name / 043 40 I NBXf M
Location ans Ref Data, I01-23 first 23 characters of ADDRESS 1
24-38 first 15 characters of City
(= first 15 characters of ADDRESS 4)
39-40 GB
Note: this field can be sent to LINK in mixed case (except GB
which must be in upper case)
Card Acceptor Terminal I 041 I ans 8 [Outlet fromIComprises 6 digit outlet id (group_id) + 2 digit terminal id M
Identification system I(node_id)
Conversion Rate, o10 I on 8 INot required - foreign currency transactions are not
ICardholder Billing Isupported by NBX.
ICryptogram (ARQC) 6 I oh 16 icc [Computed by ICC for on-line application
ICryptogram Amount 147 I on 12 \cc [Transaction amount used by ICC in generating cryptogram
Icryptogram Currency Code] 148 I ni 3 icc Contains transaction currency code used by ICC in
lgenerating cryptogram for an ICC transaction
ICryptogram Transaction I 144 I ni 2 \cc Contains transaction type used by ICC in generating the c
Type Icryptogram for an ICC transaction
Currency Code, Cardholder] 051 I an 3 INot required - foreign currency transactions are not
Billing Isupported by NBX
ICurrency Code, o49 I an 3 I Clerk at only 826 (GBP) will be accepted by LINK initially. NBX will I M
Transaction outlet translate GBP code received from Counters to 826 (using
ISO 4217 standard) for LINK. Other values may be added to
Currency Code CPF Table if required at a later date, and will
be translated in the same way
Date, Expiration o14 I vvmm I 4 I Clerkat [May be required where the card data is manually entered, c
Outlet [determined by the reference data at the counter. This will only
be for deposits
Date, Local Transaction I 013 I MMDD I 4 I Outlet fromIAs printed on receipt, transaction request date in Local Time I M
System
Date, Settlement ots I mmo I 4 I NBX, then INBX sets in request to Acquirer's settlement date, LINK sets I _M
LINK Iin response to Switch settlement date
The reversal message will contain the original, NBX set
Settlement Date.
Created on 15/08/2005 Version 3.0 Page 18 of 46
© Post Office™ 2004-2005
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NBX - LINK Application Project: EMV - Banking and Retail
Interface Specification (AIS)
p (IS) doc ret: ——_-NB/IFS/024
COMMERCIAL IN CONFIDENCE
File Name 101 I ans 17 Not appropriate to messages passed on this interface.
File Update Code 091 I an 1 Not appropriate to messages passed on this interface.
Forwarding Institution 033 I on ou Not required, since NBX is an Acquirer only
Identification Code
fentification Ci ne
Info Text 124 I ans 255 I Sender IContains up to first 255 bytes of the message rejected by the
LULVAR sender (either NBX or LINK
Issuer Application Data 134 h 64 Icc [Unique ICC related card data for card scheme (LINK) c
LLVAR
[Issuer Authentication Data I 139 I fh 32 I Issuer [A value computed by the Issuer to allow the ICC to
LLVAR authenticate the issuer returning the response. Comprises
two sub-fields:
1m Sub-field 1 - ARPC (format h16) ~ must be included in
a response to a message where the ARQC has been
verified successfully by the Issuer
Im Sub-field 2 - Optional Data (format ..h16)
leeuer Script 142 h 255 I Issuer IContains commands for transmission to ICC from Issuer
LLLVAR
Issuer Trace Id 126 I ans 6 Issuer _IIssuer specified transaction identifier. Note: The field is
FIXED length 6 but with the var field header ie LLLnnnnnn
LLLVAR
Merchant Type 01 I on 4 Not required for NBX transactions - POS Transactions Only
Message Authentication I 064 I h 16 INot currently supported by LINK
Code
Message Authentication I 128 I h 16 Not appropriate to messages passed on this interface.
Code
Message Security Code I 096 I ans 8 Sender Password to network management requests. Value set =
I435TT (both directions)
Network Management 125 I ans 60 I Sender Additional information required for key change and key
Information LULVAR verification
Im Positions 01-32 - 32 byte working key
Positions 33-38 - check value
m__ Positions 39-60 - Spaces (optional)
Network Management o70 I on 3 Codes to be used for 0800/0810 messages are defined in M
Information Code section 4.2.10.
Original Data Elements 090 n 42 NBX Positions 1-4 will be set to 0200, remaining positions are zero
filled
Created on 15/08/2005 Version 3.0 Page 19 of 46
© Post Office™ 2004-2005
NBX - LINK Application Project: EMV — Banking and Retail
Interface Specification (AIS) Doc Ref:
NB/IFS/024
COMMERCIAL IN CONFIDENCE
FUJ00003484
FUJ00003484
PIN Data
052
16
Outlet from
customer
Customer PIN Entered by customer & encrypted using ISO I C
9564-1 Format 0 as defined in ANSI X9.8. Not supplied for
verification by signature or deposit transactions (as no PIN
authentication of the customer is undertaken)
Point of Service Condition
Code
025
Outlet
To initially be set by NBX (from Ref Data) to 54 (Non ICC M
Capable Branch ATM). 55 must be used to indicate ICC
Capable Branch ATM when chip read support added.
Point of Service Data
061
20
NBX
[Subfield 1 will be set to: M
8 Mag. stripe & key entry (counter not ICC enabled)
9—Mag. stripe, ICC & key entry (counter ICC enabled)
Subfield 2 will be set to:
1-PIN,
0 —No electronic authentication (assumed for deposit)
[Subfield 3 will be set to 0 — No capture
[Subfield 4 will be set to 1 — On premises of card acceptor,
jattended,
[Subfields 5 and 6 will be set to 01 — Cardholder present, card
present,
[Subfield 7 will be set to: 2 - Magnetic stripe, 5 - ICC, 6—
Manual Entry
[Subfield 8 will be set to 1 — PIN, 0 — No PIN (if deposit
transaction)
[Subfield 9 will be set to 3 (Authorising agent = issuer) for
PIN, 0 (No authentication) if not PIN (i.e. for a deposit)
[Subfield 10 = 1 (none) or 3 (ICC)
[Subfield 11 = 0 (unknown — mixed print & display capability,
lover time)
[Subfield 12 = C (pin capture length is up to 12 - hiw
capability, usage is likely to be 4 digits only) if PIN entry
capability, 0 if no PIN entry capability (i.e. for a deposit)
Created on 15/08/2005
© Post Office™ 2004-2005
Version 3.0 Page 20 of 46
FUJ00003484
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NBX - LINK Application Project: EMV - Banking and Retail
Interface Specification (AIS)
p (IS) doc ret: ——_-NB/IFS/024
COMMERCIAL IN CONFIDENCE
Point of Service Entry Mode] 022 I n 3 IOutlet fromIDigits 1-2 will be: M
system
101 (Manual entry)
105 (ICC)
90 (Mag Stripe, Track 2 read and fully transmitted, includes
idowngraded ICC cards)
Digit 3 will be:
1 (PIN entry capability)
2 (No PIN entry capability) - assumed for deposit
Point of Service PIN 026 n oy Not appropriate to messages passed on this interface - POS
Capture Code Transactions Only
Primary Account Number 002 n 19 IOutlet from}Read from ICC for an ICC transaction, read from Track 2 M
card/Clerk Idata if card swiped, entered by the clerk when card details
LLVAR at Outlet Imanually entered.
[Identifies particular card, customer account or relationship]
Processing Code 003 n 6 NBX INBX will set digits 1 and 2 to M
01 for Withdrawal
31 for Balance Enquiry
21 for cash deposit
24 for cheque deposit.
[Digits 3 to 6 will be set to zero (default). All 6 digits passed by}
INBX and LINK.
Replacement Amounts 095 I an 42 Not required - partial reversals not supported by NBX
Response Code 039 an 2 (Code indicating transaction step outcome. Source dependent M
lon transaction type.
Retrieval Reference 037 an 12 NBX Additional transaction identifier, assigned by NBX. It will be M
Number* lunique for a terminal ID, at least within 10 years.
Digits 01-04 set to date (YDDD)
Digits 05-06 set to 00
Digits 07-12 set to a 6 digit cycling number generated at eachI
counter
‘ Fields Systems Trace Audit Number (011), Time Local Transaction (012), Retrieval Reference Number (037) and Card Acceptor Terminal Identification (041) are used to uniquely identify transactions
Created on 15/08/2005
© Post Office™ 2004-2005
Version
3.0 Page 21 of 46
FUJ00003484
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NBX - LINK Application Project: EMV — Banking and Retail
Interface Specification (AIS)
p (IS) doc ret: ——_-NB/IFS/024
COMMERCIAL IN CONFIDENCE
[Systems Trace Audit on n 6 NBX Transaction identifier, assigned by NBX within the request, I M M
Number land included in all subsequent messages relating to that
transaction ([A1] response and [E 1] / [2] reversal
messages),
‘Terminal Capability Profile I 130 h 6 Outlet IRequired for ICC transactions - indicates card data input, c
ICVM and security capabilities of terminal
Terminal Country Code 145 n 3 Outlet ICountry Code (ISO value) of terminal carrying out ICC c
transaction — value = 826
Terminal Serial Number 133 I an 8 Outlet [Unique and permanent identification number of chip terminal
‘Terminal Transaction Date I 146 n 6 Outlet Contains transaction date in format YYMMDD used by ICC
in generating the cryptogram for ICC transaction
‘Terminal Verification 131 h 10 Outlet Status of different ICC functions as seen from terminal c
Results (TVR)
Time, Local Transaction I 012 n 6 Outlet fromIAs printed on receipt, transaction request time in Local Time I M
System fin format hhmmss
Track 2 Data 035 z 37 I Outlet fromITrack 2 image. Will not be present where card details have c
LivAR card Ibeen manually entered
Transmission Date and 007 n 10 I Sender IDate and time of transmission of the message (not carried M M
Time Horward from previous messages), expressed in GMT or BSTI
Jas appropriate, Format MMDDhhmmss
Unpredictable Number 132 h 8 I Generated IValue providing variability and uniqueness to generation of c
by terminal Ithe application cryptogram for an ICC transaction
Created on 15/08/2005 Version 3.0 Page 22 of 46
© Post Office™ 2004-2005
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4.2 Data Interpretations
This section contains the definition of each message type to be sent over this interface. The Message
Element column lists those elements required for the message by Horizon name, and relates to list in Section
4.1.
The Required column in the message definition tables within this section contain the following codes:
Code Meaning
M The element is mandatory and must be present in this message
c The element is conditional for this message, and the condition to be applied is
stated in the Conditions column. If the condition is true, the element must be
present in the message, otherwise the element must not be present in the
message. It should be noted that the receiving system may not be able to
assess whether the condition has been met, in which case it must be able to
interpret the presence or non-presence of the element according to appropriate
business rules.
fe} Optional (see Message Definitions below for specific rules)
The Conditions column lists the conditions for inclusion of a conditional message element; inclusion of the
element may depend on details of the transaction type, or simply whether the data is available to the sending
system.
The message definitions given in the sections below do not include primary bitmaps. Primary, secondary and
tertiary bitmaps will be used as required by the LINK Switch Service Interchange Standard (LISS5), (Ref. [1]).
It is essential that developers of this interface also refer to the LINK Switch Service Interchange Standard
(LISS), (Ref. [1]) and the Horizon - LINK Mapping document, (Ref. [5]) for further details of data derivation
and use.
A greyed out row in the following tables means that the field is not required and may not be populated in
messages from NBX to LINK. The NBX will log any such fields received from LINK but will not process them
further.
NBX - LINK Application
Interface Specification (AIS) Doc Ref:
COMMERCIAL IN CONFIDENCE
Project: EMV - Banking and Retail
NB/IFS/024
FUJ00003484
FUJ00003484
4.2.1 [R3] - Balance Enquiry
4.2.1.1 Overview
This message is sent by the NBX to LINK. The message requests a balance enquiry transaction.
The [R3] Balance Enquiry message maps to the following LINK message:
e 0100 - Balance Enquiry
4.2.1.2 Message Definition
Message Element Bitmap Required ] Notes / Conditions
Reference
Bit Map Secondary 001 Cc
Primary Account Number (002 M
Processing Code 003 M 310000 for Balance Enquiry
‘Amount, Cardholder Billing 006 Not required
Transmission Date and Time 007 M
Conversion Rate, Cardholder Billing 010 Not required
Systems Trace Audit Number O11 M
Time, Local Transaction 012 M
Date, Local Transaction 013 M
Date, Expiration 014 Cc Required for manually key entered balance enquiry
transaction
Date, Settlement 015 M ‘Acquirers settlement date
Point of Service Entry Mode 022 M Please refer to 4.1.2 for values
Application PAN Sequence Number 023 Cc Required for ICC transactions, or if the card's issue
number has been manually entered
Point of Service Condition Code 025 M Please refer to 4.1.2. for contents of the field
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required
ode
Track 2 Data 035 Cc Will not be present where card details manually
entered.
Retrieval Reference Number 037 M Please refer to 4.1.2. for contents of the field
Card Acceptor Terminal Identification 041 M
Card Acceptor Name / Location 043 M
Currency Code, Transaction 049 M
Currency Code, Cardholder Billing 051 Not required
PIN Data 052 Cc Required if PIN used
‘Advice / Reversal Reason Code (060 Cc Required for ICC transactions
Point of Service Data 061 M Please refer to 4.1.2 for values
Message Authentication Code 064 Not to be sent fo LINK for this implementation.
Bit Map Tertiary 065 Cc Required for ICC transactions
‘Terminal Capability Profile 130 Cc Required for ICC transactions
‘Terminal Verification Results 131 Cc Required for ICC transactions
Unpredictable Number 132 Cc Required for ICC transactions
‘Terminal Serial Number 133 ° Optional for ICC transaction - to be inserted if available
Issuer Application Data 134 Cc Required for ICC transactions
Cryptogram (ARQC) 136 Cc Required for ICC transactions
Application Transaction Counter 137 Cc Required for ICC transactions
Application Interchange Profile 138 Cc Required for ICC transactions
Cryptogram Transaction Type 144 Cc Required for ICC transactions
Terminal Country Code 145 Cc Req'd for ICC transactions — see 4.1.2 for value
‘Terminal Transaction Date 146 Cc Required for ICC transactions
Cryptogram Amount 147, c Required for ICC transactions
Cryptogram Currency Code 148 Cc Required for ICC transactions
Message Authentication Code 192, Not requirediin this implementation
Created on 15/08/2005 Version 3.0 Page 24 of 46
© Post Office™ 2004-2005
NBX - LINK Application
Interface Specification (AIS) Doc Ref:
COMMERCIAL IN CONFIDENCE
Project: EMV - Banking and Retail
NB/IFS/024
FUJ00003484
FUJ00003484
4.2.2 [R3] - Financial Transaction Request - Withdrawal
4.2.2.1 Overview
This message is sent by the NBX to LINK. The message requests a withdrawal transaction.
The [R3] Financial Transaction Request message maps to the following LINK message:
e 0200 - Financial Transaction Request.
4.2.2.2 Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 Cc Required for ICC transactions
Primary Account Number (002 M
Processing Code 003 M 010000 for Financial Transaction
‘Amount, Transaction 004 M
‘Amount, Cardholder Billing 006 Not required
Transmission Date and Time 007 M
Conversion Rate, Cardholder Billing 010 Not required
Systems Trace Audit Number om M
Time, Local Transaction 012 M
Date, Local Transaction 013 M
Date, Expiration 014 S Not required
Date, Settlement 015 M ‘Acquirer’s settlement date
Point of Service Entry Mode 022 M Please refer to 4.1.2 for values.
Application PAN Sequence 023 Cc Required for ICC transactions, or if the card's issue
number has been manually entered
Point of Service Condition Code 025 M Please refer to 4.1.2 for contents of the field
‘Amount, Transaction Fee 028 Not required - acquirer charge will not be used
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required.
Code
Track 2 Data 035 Cc Will not be present where card details manually
entered.
Retrieval Reference Number 037 M Please refer to 4.1.2. for contents of the field
Card Acceptor Terminal Identification 041 M
Card Acceptor Identification Code 042 M
Card Acceptor Name / Location 043 M
Currency Code, Transaction 049 M
Currency Code, Cardholder Billing 051 Not required
PIN Data 052 Cc Required if PIN used
‘Advice / Reversal Reason Code (060 Cc Required for ICC and fallback transactions
Point of Service Data 061 M Please refer to 4.1.2 for values
Message Authentication Code 064 Not to be sent fo LINK for this implementation.
Bit Map Tertiary 065 Cc Required for ICC transactions
‘Authorisation Data 123 Cc Sub Field 18 contains start date of card ifit exists and
card details are manually entered
Terminal Capability Profile 130 Cc Required for ICC transactions
Terminal Verification Results 131 Cc Required for ICC transactions
Unpredictable Number 132 Cc Required for ICC transactions
‘Terminal Serial Number 133 ° Optional for ICC transaction
Issuer Application Data 134 Cc Required for ICC transactions
Cryptogram (ARQC) 136 Cc Required for ICC transactions
Application Transaction Counter 137, Cc Required for ICC transactions
Application Interchange Profile 136 Cc Required for ICC transactions
Cryptogram Transaction Type 144 Cc Required for ICC transactions
Terminal Country Code 145) Cc Req'd for ICC transactions — see 4.1.2 for value
Terminal Transaction Date 146 Cc Required for ICC transactions
Cryptogram Amount 147 Cc Required for ICC transactions
Cryptogram Currency Code 148 Cc Required for ICC transactions
Message Authentication Code 192 Not required in this implementation
Created on 15/08/2005 Version 3.0 Page 25 of 46
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FUJ00003484
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NBX — LINK Application Project: EMV — Banking and Retail
Interface Specification (AIS) Doc Ref: NB/IFS/024
COMMERCIAL IN CONFIDENCE
4.2.3. [R3] - Financial Transaction Request - Deposit
4.2.3.1 Overview
This message is sent by the NBX to LINK. The message details a cash deposit or cheque deposit
request. Mixed deposits ie cash and cheque in one transaction will not be supported on this interface.
The [R3] Financial Transaction Request message maps to the following LINK message:
e 0200 - Financial Transaction Request
4.2.3.2 Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 Cc Required for ICC transactions
Primary Account Number (002 M
Processing Code 003 M 210000 for cash deposit
240000 for cheque deposit
‘Amount, Transaction 004 M
‘Amount, Cardholder Billing 006 Not required
‘Transmission Date and Time 007 M
Conversion Rate, Cardholder Billing 010 Not required
Systems Trace Audit Number on M
Time, Local Transaction 012 M
Date, Local Transaction 013 M
Date, Expiration 014 c Required for manually key entered deposit transaction
Date, Settlement 015 M ‘Acquirer’s settlement date
Point of Service Entry Mode 022 M Please refer to 4.1.2 for values
Application PAN Sequence Number 023 Cc Required for ICC transactions, or if the card's issue
number has been manually entered
Point of Service Condition Code 025 M Please refer to 4.1.2 for contents of the field
‘Amount, Transaction Fee 028 Not required - acquirer charge will not be used
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required
Code
Track 2 Data 035 c Will not be present where card details manually
entered.
Retrieval Reference Number 037 M Please refer to 4.1.2 for contents of the field
Card Acceptor Terminal Identification 041 M
Card Acceptor Identification Code 042 M
Card Acceptor Name / Location 043 M
Currency Code, Transaction 049 M
Currency Code, Cardholder Billing 051 Not required
PIN Data 052 Not required for deposit transactions
‘Advice / Reversal Reason Code 060 Cc Required for ICC transactions and fallback
transactions
Point of Service Data 061 M Please refer to 4.1.2 for values.
Message_Authentication_Code 064 Not to be sent to LINK for this implementation.
Bit Map Tertiary 065 Cc Required for ICC transactions
Authorisation Data 123 c Sub Field 17 contains 1 for cheque deposit (number of
cheques) and value of transaction inserted.
Sub Field 18 contains start date of card if it exists and
card details are manually entered
‘Terminal Capability Profile 130 Cc Required for ICC transactions
Terminal Verification Results 131 Cc Required for ICC transactions
Unpredictable Number 132 Cc Required for ICC transactions
Terminal Serial Number 133 ° Optional for ICC transaction — to be inserted if
available
Issuer Application Data 134 Cc Required for ICC transactions
Cryptogram (ARQC) 136 Cc Required for ICC transactions
‘Application Transaction Counter 137, Cc Required for ICC transactions
Application Interchange Profile 138 Cc Required for ICC transactions
Created on 15/08/2005 Version 3.0 Page 26 of 46
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FUJ00003484
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NBX — LINK Application Project: EMV — Banking and Retail
Interface Specification (AIS)
P (AIS) Doc Ret: NB/IFS/024
COMMERCIAL IN CONFIDENCE
Cryptogram Transaction Type 144 c Required for ICC transactions
Terminal Country Code 145, c Req'd for ICC transactions — see 4.1.2 for value
‘Terminal Transaction Date 146 Cc Required for ICC transactions
Cryptogram Amount 147 Cc Required for ICC transactions
Cryptogram Currency Code 148 Cc Required for ICC transactions
Message Authentication Code 192, Not required in this implementation
Created on 15/08/2005 Version 3.0 Page 27 of 46
© Post Office™ 2004-2005
COMMERCIAL IN CONFIDENCE
NBX - LINK Application
Interface Specification (AIS)
Project: EMV - Banking and Retail
Doc Ref: NB/IFS/024
FUJ00003484
FUJ00003484
4.2.4
4.2.4.1
4.2.4.2
Overview
[A1] - Balance Enquiry Response
This message is sent by LINK to the NBX. The message contains a balance enquiry response.
The [A1] Balance Enquiry Response message maps to the following LINK messages:
« 0110 - Balance Enquiry Response
© Post Office™ 2004-2005
Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 M
Primary Account Number (002 M Echoed from the request message
Processing Code (003 M Echoed from the request message
‘Amount, Cardholder Billing 006 Not required
‘Transmission Date and Time 007 M
Conversion Rate, Cardholder Billing 010 Not required
Systems Trace Audit Number on M Echoed from the request message
Time, Local Transaction 012 M Echoed from the request message
Date, Local Transaction 013 M Echoed from the request message
Date, Settlement 015 M Switch settlement date
Application PAN Sequence 023 Cc Echoed from the request message if present
‘Acquiring Institution Identification 032 M Echoed from the request message
Code
Forwarding Institution Identification 033 Not required because not in request.
Code
Retrieval Reference Number 037 M Echoed from the request message
Response Code 039 M
Card Acceptor Terminal Identifier 041 M Echoed from the request message
Currency Code, Transaction’ 049 M Echoed from the request message
Currency Code, Cardholder Billing 051 Not required
‘Additional Amounts 054 M For a decline, the length of this field must be set to
‘000'
Bit Map Tertiary 065 Cc Required for ICC transactions
‘Account Identification 1 102 M Not used by NBX
Authorising Agent Institution Id Code 113 M
Issuer Trace Id 126 M
Message Authentication Code 128 Not fo be sent to LINK for this implementation.
Application Transaction Counter 137 Cc Required for ICC transactions
Issuer Authentication Data 139 Cc Required for ICC transactions (omitted if cannot be
generated)
Issuer Script 142 At Issuer's discretion
Message Authentication Code 192 Not required in this implementation
Created on 15/08/2005 Version 3.0 Page 28 of 46
FUJ00003484
FUJ00003484
NBX — LINK Application Project: EMV ~ Banking and Retail
Interface Specification (AIS)
P (AIS) Doc Ret: NB/IFS/024
COMMERCIAL IN CONFIDENCE
4.2.5 [A1] - Financial Transaction Request Response - Withdrawal
4.2.5.1 Overview
This message is sent by LINK to the NBX. The message contains a withdrawal request response.
The [A1] Financial Transaction Request Response message maps to the following LINK message:
e 0210 - Financial Transaction Request Response.
Note that LINK will never return a partial authorisation.
4.2.5.2 Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 M
Primary Account Number (002 M Echoed from the request message
Processing Code (003 M Echoed from the request message
‘Amount, Transaction 004) M Echoed from the request message
‘Amount, Cardholder Billing 006; Not required
Transmission Date and Time 007 M
Conversion Rate, Cardholder Billing 010 Not required
Systems Trace Audit Number on M Echoed from the request message
Time, Local Transaction 012 M Echoed from the request message
Date, Local Transaction 013 M Echoed from the request message
Date, Settlement 015: M Switch settlement date
Application PAN Sequence 023 Cc Echoed from the request message if present
‘Amount, Transaction Processing Fee 030 Cc Field will not be returned by LINK in a LINK denied
transaction.
‘Acquiring Institution Identification 032 M Echoed from the request message
Code
Forwarding Institution Identification 033 Not required because not in request.
Code
Retrieval Reference Number 037 M Echoed from the request message
Response Code 039) M
Card Acceptor Terminal Identifier 41 M Echoed from the request message
Currency Code, Transaction 049) M Echoed from the request message
Currency Code, Cardholder Billing 051 Not required
‘Additional Amounts 054 c Required if available from issuer
Bit Map Tertiary 065; c Required for ICC transactions
‘Account Identification 4 102 M Not used by NBX
Authorising Agent Institution Id Code 113 M
‘Authorisation Response Data 124 Not required in NBX implementation
Issuer Trace Id 126 M
Message Authentication Code 128 Not to be sent fo LINK for this implementation.
‘Application Transaction Counter 137 Cc Required for ICC transactions
Issuer Authentication Data 139 c Required for ICC transactions (omitted if cannot be
generated)
Issuer Script 742 ie) At Issuer's discretion
Message Authentication Code 192 Not required in this implementation
Created on 15/08/2005 Version 3.0 Page 29 of 46
© Post Office™ 2004-2005
FUJ00003484
FUJ00003484
NBX — LINK Application Project: EMV ~ Banking and Retail
Interface Specification (AIS)
P (AIS) Doc Ret: NB/IFS/024
COMMERCIAL IN CONFIDENCE
4.2.6 [A1] - Financial Transaction Request Response - Deposit
4.2.6.1 Overview
This message is sent by LINK to the NBX. The message contains a deposit request response.
The [A1] Financial Transaction Request Response message maps to the following LINK message:
e 0210 - Financial Transaction Request Response.
Note that LINK will never return a partial authorisation.
4.2.6.2 Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 M
Primary Account Number (002 M Echoed from the request message
Processing Code (003 M Echoed from the request message
‘Amount, Transaction 004) M Echoed from the request message
‘Amount, Cardholder Billing 006; Not required
Transmission Date and Time 007 M
Conversion Rate, Cardholder Billing 010 Not required
Systems Trace Audit Number on M Echoed from the request message
Time, Local Transaction 012 M Echoed from the request message
Date, Local Transaction 013 M Echoed from the request message
Date, Settlement 015: M Switch settlement date
Application PAN Sequence 023 Cc Echoed from the request message if present
‘Amount, Transaction Processing Fee 030 Cc Field will not be returned by LINK in a LINK denied
transaction.
‘Acquiring Institution Identification 032 M Echoed from the request message
Code
Forwarding Institution Identification 033 Not required because not in request.
Code
Retrieval Reference Number 037 M Echoed from the request message
Response Code 039) M
Card Acceptor Terminal Identifier 41 M Echoed from the request message
Currency Code, Transaction 049) M Echoed from the request message
Currency Code, Cardholder Billing 051 Not required
‘Additional Amounts 054 c Required if available from issuer
Bit Map Tertiary 065; c Required for ICC transactions
‘Account Identification 4 102 M Not used by NBX
Authorising Agent Institution Id Code 113 M
‘Authorisation Response Data 124 Not used in the NBX implementation
Issuer Trace Id 126 M
Message Authentication Code 128 Not to be sent fo LINK for this implementation.
‘Application Transaction Counter 137 Cc Required for ICC transactions
Issuer Authentication Data 139 c Required for ICC transactions (omitted if cannot be
generated)
Issuer Script 742 ie) At Issuer's discretion
Message Authentication Code 192 Not required in this implementation
Created on 15/08/2005 Version 3.0 Page 30 of 46
© Post Office™ 2004-2005
FUJ00003484
FUJ00003484
NBX — LINK Application Project: EMV ~ Banking and Retail
Interface Specification (AIS)
P (AIS) Doc Ret: NB/IFS/024
COMMERCIAL IN CONFIDENCE
4.2.7 [E1] - Reversal Request
4.2.7.1 Overview
This message is sent by the NBX to LINK when a financial transaction that has been processed by the
issuer needs to be reversed.
The [E1] message maps to the following LINK messages:
* 0420 - Reversal Request
e 0421 - Reversal Repeat.
A Reversal Request [E1] can only be generated when the [A1] message to be reversed can be mapped
against a [R3] request.
Reversal Requests may be sent up to a (configurable) period, initially set to 5 days, after the original
transaction to which it refers.
Note that partial reversals are not supported over this interface.
4.2.7.2 Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 M
Primary Account Number 002 M
Processing Code 003 M Copied from the [Ai]
‘Amount, Transaction 004 M
‘Amount, Cardholder Billing 006 Not required
Transmission Date and Time 007 M
Conversion Rate, Cardholder Billing 010 Not required
Systems Trace Audit Number om M
Time, Local Transaction O12 M
Date, Local Transaction 013 M
Date, Expiration 014 c Required if present on original transaction. Copied
from original transaction
Date, Settlement 015 M Copied from the [[R3]
Merchant type 018 Not required
‘Acquiring Institution Country Code 019 Not required
Point of Service Entry Mode 022 M
‘Application PAN Sequence Number 023 Cc Required if present on original transaction
Point of Service Condition Code 025 M
‘Amount, Transaction Fee 028 Not required - acquirer charge will not be used
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required
Code
Track 2 Data 035 Cc Required if present on original transaction
Retrieval Reference Number 037 M
‘Authorisation Identification Response. 038 Not required
Response Code 039 M Copied from the [A1]
Card Acceptor Terminal Identifier 041 M
Card Acceptor Identification Code 042 M
Card Acceptor Name / Location 043 M
Currency Code, Transaction 049 M
Currency Code, Cardholder Billing 051 Not required
‘Advice / Reversal Reason Code 060 M
Point of Service Data 061 M
Bit Map Tertiary 065 Cc Required for ICC transactions if any of the optional
fields included
Original Data Elements 090 M
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Replacement Amounts 095, Not required
‘Account Identification 1 102 M
Authorisation Response Data 124 Not used in the NBX implementation
‘Authorisation Data 123 Cc Required if present on original transaction
Issuer Trace Id 126 M
Terminal Capability Profile 130 ° Optional for ICC transactions. Copied from original
transaction
Terminal Verification Results TH ) Optional for ICC transactions.
This should contain the latest TVR which may be
different to that in the original request. If the latest TVR
is unavailable, the value in the original request should
be used
Unpredictable Number 132 ) Optional for ICC transactions. Copied from original
transaction
Terminal Serial Number 13 Optional for ICC transactions. Copied from original
transaction
Issuer Application Data 134 Optional for ICC transactions.
This should contain the latest [AD which may be
different to that in the original request. If the latest IAD
is unavailable, the value in the original request should
be used
Cryptogram (ARQC) 136 ° Optional for ICC transactions.
This should contain the ARQC from the 2 Gen. AC
command or if unavailable, the ARQC from the 1*
Gen. AC command
‘Application Transaction Counter 137 Co) Optional for ICC transactions. Copied from original
transaction
‘Application Interchange Profile 138 [) Optional for ICC transactions. Copied from original
transaction
Cryptogram Transaction Type 144 ) Optional for ICC transactions. Copied from original
transaction
Terminal Country Code 145 ) Optional for ICC transactions. Copied from original
transaction
Terminal Transaction Date 146 ) Optional for ICC transactions. Copied from original
transaction
Cryptogram Amount 147 ° Optional for ICC transactions. Copied from original
transaction
Cryptogram Currency Code 148 ° Optional for ICC transactions. Copied from original
transaction
Message Authentication Code 792 Not required in this Implementation
Note: NBX does not include any of the Optional fields.
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4.2.8
4.2.8.1
This message is sent by LINK to the NBX in response to a reversal request from the NBX.
4.2.8.2
Overview
The [E2] message maps to the LINK message 0430.
[E2] - Reversal Request Response
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Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 M
Processing Code 003 M Echoed from the 042x message.
‘Amount, Transaction 004 M Echoed from the 042x message.
‘Transmission Date and Time 007 M Echoed from the 042x message.
Systems Trace Audit Number on M Echoed from the 042x message.
Time, Local Transaction 012 M Echoed from the 042x message.
Date, Local Transaction 013 M Echoed from the 042x message.
Date, Settlement 015 M Echoed from the 042x message.
Application PAN Sequence 023 Cc Required if present on original transaction
Acquiring Institution Identification 032 M Echoed from the 042x message.
Code
Forwarding Institution Identification 033 Not required
ode
Retrieval Reference Number 037 M Echoed from the 042x message.
Response Code 039 M
Currency Code, Transaction (049 M Echoed from the 042x message.
Bit Map Tertiary 065 Cc Required for ICC transactions
Original Data Elements (090 M Echoed from the 042x message.
Replacement Amounts. 095 Not required
Authorisation Response Data 121 Not required
Authorisation Data 123 Not required
Issuer Trace Id 126 M Echoed from the 042x message.
‘Application Transaction Counter 137 Cc Required for ICC transactions if present in reversal
request. Copied from request
Cryptogram Transaction Type 144 ° Optional for ICC transactions. Copied from original
transaction
Message Authentication Code 192 Not required in this implementation
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4.2.9 Administration Advice (0620)
4.2.9.1 Overview
Administration advice messages are sent to/from LINK in order to initiate investigation of a problem by
either LINK or the NBX.
The Administration advice message maps to LINK message 0620.
4.2.9.2 Message Definition
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 M
‘Transmission Date and Time 007 M
Systems Trace Audit Number O11 M
Network Management Information 070 M Set to be 900
Code
Info Text 124 Mw
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4.2.10 Network Management Messages (0800 / 0810)
The following Network Management Messages will be exchanged between LINK and the NBX:
e 0800 - Network Management Request Message
0810 - Network Management Response Message
They are used for the following purposes (followed by associated Network Management Information Code):
The
Sign On, acquirer, LINK initiated (061)
Sign On, acquirer, NBX initiated (071)
Sign Off, acquirer, LINK initiated (062)
Sign Off, acquirer, NBX initiated (072)
End of Day, Acquirer from LINK (261)
Handshake, Acquirer from LINK (361)
Handshake, Acquirer from NBX (371)
Key Change - Acquirer Zone from LINK (161)
Key Change Request - Acquirer Zone from NBX (181)
Online Key Verification Acquirer ZMK from LINK (199)
usage, sequence and inter-relation between these and other message is defined in the body of the
document “LINK Switch Service Interchange Standard (LIS5)"(Ref. [1]) and in Appendix C1 of the “LISS
Security Standard” section of that document under Network Management Option 2 (Ref. [7]).
4.2.10.1 Network Management Request (0800)
Message Element Bitmap Required] Notes / Conditions
Reference
Bit Map Secondary 001 M
Transmission Date and Time 007 M.
Systems Trace Audit Number O11 M Set for this transaction — a new STAN is used when a
0800 message is repeated
Network Management Information 070 M Values will depend on message purpose, as described
Code above.
Message Security Code 096 Cc Required for key change, key verification, logon and
logoff
Network Management Information 425 Cc Required for key change and key verification
4.2.10.2 Network Management Request Response (0810)
Message Element Bitmap. Required I Notes / Conditions
Reference
Bit Map Secondary 001 M
Transmission Date and Time 007 M.
Systems Trace Audit Number O11 M Echoed from the 0800
Response Code 039 M
Network Management Information Code 070, M TThis is echoed from the 0800 received message
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4.2.11. LREC - Reconciliation File
The LREC reconciliation file which is sent from LINK to the NBX is in accordance with the LINK Reconciliation
File Specification (LREC) Standard Formats, (Ref. [2]). The file transfer mechanism and conditions of transfer
are described in the NBX — LINK Technical Interface Specification (Ref. [4]).
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5 Transfer Structure
5.1 Transfer Grouping
The following figure shows the end to end message sequences, using the RACE (Request / Authorise /
Confirm / Exception) model, for all application messages between the NBX and the LINK Switch. No
knowledge is assumed of the interface between LINK and its member financial institutions.
[ 4 I
0800 ] [0810
oD}] I[EoD} LREC
Horizon a -
Counter Systems DRS
Figure 1 - LINK Message Flows in the Network Banking Environment
A 0620 message may be issued by the NBX in response to all messages from LINK (for simplicity, only one
such flow is shown on the diagram).
Reversals (0420 messages) are not sent from NBX to LINK unless and until an approved response (0210
message) has been received from LINK. Repeat Reversals (0421) are only sent in the event that the prior
0420 (or 0421) reversal messages have not had a response processed at the NBX.
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Each incoming request is time-stamped as it is received by LINK. The settlement day in which the transaction
will be processed will depend on whether the transaction was time-stamped before or after LINK transmitted
the 0800 cut-over message (irrespective of whether a subsequent 0810 message was received).
The interface should be resilient to the transfer of duplicate messages; in practice, however, this should only
happen after failure and recovery of either end of the interface.
LINK will not validate transmission date and time in messages against the date and time that messages are
received.
The interface details are also described in the NBX — LINK Technical Interface Specification (Ref. [4])
5.2 Transfer Structure
The messages defined in this AIS will be exchanged in accordance with Section 3 of the LINK Switch Service
Interchange Standard (LIS5), (Ref. [1]), which describes the use of Message Type Identifier, Bit Map and Data
Elements in the message structure. Note that the messages exchanged over this interface use the third bit
map for the ICC data elements.
Messages for one transaction may be interleaved with messages for any other transaction.
5.3 Record Structure
The record structure for the messages defined in this AIS is as described in the LISS Interchange Standard,
Reference (Ref. [1]). The details are not repeated here.
The record structure for the LREC file passed over this interface is described in LINK Reconciliation File
Specification (LREC) Standard Format, (Ref. [2]). The details are not repeated here.
5.4 Sequences
Figure 1 above (see Section 5.1) shows the end to end message sequences of all the messages supported by
this AIS, from the PO Outlet to the issuing financial institution. Further detail relating specifically to the NBX -
LINK connection can be found in the NBX — LINK Technical Interface Specification (Ref. [4]). The interface
must be resilient to the disconnection or loss of any part of the total network banking environment for short or
extended periods.
5.5 Data Volumes
Data Rates and Volumes over this interface are addressed through the NB Volume Model Comparisons, (Ref.
(3]).
5.6 Data Authentication
For this implementation, Message Authentication Codes (MACs) will not be included in the messages sent
between the NBX and LINK.
5.7 Data Dictionary
The Data Elements used on this interface are defined and described within Appendix G of the LINK Switch
Service Interchange Standard (LISS), (Ref. [1]).
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6 Security of Transmitted Data
The security standards for the LINK-NBX interface are described in the NBX — LINK Technical Interface
Specification (Ref. [4]).
6.1 Protected Data
PIN blocks that pass across the interface from NBX to LINK are encrypted under an Acquirer Working Key
(AWK). This key is used in the LINK — NBX shared security zone. PIN Block encryption is translated from
internal keys to protection under this shared key using a hardware encryption module. The PIN blocks are
never rendered in clear outside the hardware module.
Acquirer Working Keys are exchanged electronically under a Acquirer Zone Master Key (AZMK) shared
between NBX and LINK. The AZMK is generated and owned by the NBX. The AWK is owned and generated
by LINK.
6.2 Encryption and Decryption Methods
PIN Block and Acquirer Working Key transmission is protected by Triple DES double length keys, 112bit plus
key check data.
All data transmitted on communication lines between the NBX and LINK is encrypted using Line Encryption
Units. LINK is responsible for the Line Encryption Units at both ends of the communication line.
6.3 Session Establishment
Sessions Establishment can be initiated by LINK or NBX. Initial Logon messages exchanges are followed by
transmission by LINK to NBX of a new AWK with a key check value protected by encryption under the shared
current AZMK.
NBX verifies the key and acknowledges it to LINK. All PIN Block data is protected by this AWK until the
session ends or the AWK is renewed.
6.4 Key Management
Key ownership is described in section 5.4 of the NBX — LINK Technical Interface Specification (Ref. [4]). LINK -
NBX Zone Management Keys are managed by the Horizon Key Management Application (KMA) with manual
processes.
According to local manual processes the NBX staff will:
e Generate three new AZMK components
e Transfer the AZMK components onto secure stationery
e Key components will contain
e Akey identifier (visible)
e Akey generation date (visible)
« Acomponent number (visible)
e 32 hex characters in eight groups of four characters — component plus check data (hidden)
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e Provide a Key Manager Key Check value
e Load the keys into the Horizon KMA
The Horizon KMA:
e Activates keys for use by Horizon Agents, which manage the TCP/IP connections to LINK.
Keys component documents must be stored and transported separately and securely.
The LINK — NBX AZMK is renewed every six months by this manual procedure. The AZMK, having been
produced as described above, is securely transported, manually, to LINK. It is expected that the resulting
online key verification message sequence would be preceded by telephone co-ordination. If this online key
verification procedure is successful, it is followed by the manual promotion of the AZMK, where the Next
AZMK becomes the Current AZMK. It is recommended that after promotion of the keys, an Operator issue a
command to drive an AWK Key change request sequence, in order to test that the verified AZMK has been
promoted by both parties.
LINK requires more than one Processor Interface (PI) to support the transaction throughput for the NBX. For
this configuration each PI will be configured to support one TCP/IP socket connection. A logical session will
be initiated by a logon, and data for that session will flow over the socket connection belonging to that Pl (see
Ref. [5] for further details). Each PI generates a LINK-NBX Acquirer Working Key (AWK) which it sends to
NBX for validation. This AWK, if validated by the NBX, is used by both socket connections between NBX and
the PI that generated it. Logical sessions for a different PI will use the AWK generated by that PI. All LINK
Pls will protect their AWK in transit to NBX by encryption using the same AZMK, during its six months of
currency.
The AWKs are changed under the following conditions (note that it is not necessary to change the AWKs as
soon as the AZMK is changed).
«Every 24 hours where the session remains active (an AWK may be changed at a set (configurable) clock
time and will remain valid until it is changed)
e Atsession initiation by either party
e On receipt by LINK of a 6" consecutive invalid PIN block on a session
e When either a NBX or LINK operator requests a key change.
Load balancing between the Pls will be performed by the NBX ensuring that the appropriate AWK for the PI is
used for PIN block translation.
There may be a short outage at the FI (typically up to 90 seconds) while the manual process for changing the
AZMK is under way.
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7 Operational Procedures
7.1 Processing Cycles
This interface relates to online message exchange to support real time financial transactions, and to the daily
transmission from LINK of the LREC file.
A transaction, which is subsequently discarded, must be logged after receipt, prior to being discarded
7.2 Transfer Initiation
All transfers defined in this AIS are automatic.
7.3 Security Procedures
Manual Procedures are required to support the above key management protocol, as described in Section 6
above.
7.4 Fallback Procedures
Fallback procedures are described in the NBX — LINK Technical Interface Specification (Ref. [4]).
Each system is responsible for its own recovery after failure. Restoration of the interface and the disposal of
stale messages (other than “must deliver” messages) is expected to be automatic. 0100, 0200, 0110 and 0210
({R] and [A]), 0620 and 0800 messages awaiting transmission at the time of failure can safely be discarded, as
the integrity of the transaction is protected by timeouts.
The only messages categorised as “must deliver” are Network Management (0800) and Reversal Request
(0420/0421) messages - see Section 6 of the LINK Switch Service Interchange Standard (LISS), (Ref. [1]).
Sign On, Sign Off, Key Change, Key Change Request and Online Key Verification 0800 messages are “must
deliver” but do not have to survive across processes when moving from active to standby sites.
Handshake 0800 messages are sent every few minutes anyway (which is sufficient).
End of Day 0800 messages are “must deliver” but note that LINK will send the message just once. Whether or
not LINK receives a response, LINK will cut over to the next Settlement Day and create LREC files
accordingly. LINK will not send another End of Day message on a PI for which no response was received.
Reversal Request 0420/0421 messages are “must deliver” messages and do have to survive when moving
from active to standby sites.
7.5 Downgrade Transactions
A ‘Downgrade’ transaction is one where an IC Card has been used at an ICC enabled terminal, but the card
issuer has advised, via POL reference data (dependent upon IIN), that the card must not be processed as ICC.
The on-line message will be formatted as a standard magnetic stripe transaction.
Nothing, apart from the Track 2 Service Code in the on-line LISS Message sent to LINK, will indicate that an
IC Card was used.
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Note that in the case of a Downgrade transaction, data must not be used from the IC, but that normal
procedures must be followed as for magnetic stripe cards.
7.6 Control
The interface must be resilient to duplicate messages, which may occur after recovery of any element in the
system, but are not otherwise expected to occur.
Lost or discarded messages are handled by timeout processing at every stage of the message sequence, to
ensure that incomplete transactions are declined if unauthorised or reversed if authorised.
The NBX will log events affecting this interface (e.g. response indicating receipt by LINK of an invalid PIN
block) to an Event Log. These events will be managed by Tivoli for escalation to the relevant Help Desk, as
appropriate to the code associated with the event.
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8 Appendix A
8.1 Response Codes and Reversal Codes
These are defined in the document Horizon — LINK Mapping (Ref. [5]).
END OF DOCUMENT
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