EMV —- Banking and Retail
NBX- CAPO Application Interface Specification (AIS)
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ROLE NAME AREA OF I SIGNATURE Date
RESPONSIBILITY
Authors Rex Dixon on behalf of I Business
Post Office Ltd Architecture
Product
Deployment
Technical
Architecture
DA Sign-off David Gray Design
(Peer Reviewer) Authority
Programme Beverley Dunn Project
Director
Delivery
CAPO Application Project:
Interface Specification Doc Ref:
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NB/FS/025
1 Document Control
1.1 Document Information
Horizon Release No:
S75
Document Title:
EMV Banking and Retail: NBX — CAPO Application Interface Specification
Document Type:
Application Interface Specification
Abstract:
This document details the application interface between the Horizon
domain and Post Office Card Account, including the interface to the ICC
Document Status: Issued
Originator & David Gray
Department:
Design Authority
Contributors:
Post Office
Distribution:
Design Authority - David Gray
POL Document Control — Post Office Programme Office
Supplier Distribution:
EDS: Steve Leek
Fujitsu Services: Gill Jackson
Client Distribution:
N/A
Table 1: Document Information
1.2 Document History
Version Date Reason for Issue Associated
WP / CT
0.1 8 Oct 2003 First working draft. Based on document
produced by IBM for NBE interfaces and
including the interface between Horizon and
the ICC
1.0 15 Oct 2003 First issued version.
11 12 Nov 2003 Updated following comments from Citibank,
also update section 1.7 and removal section
25
1.2 02 Dec 2003 I Updated following joint review on 27 Nov
1.3 26 Jan 2004 I Updated following actions from joint review
27/11/03, responses to questions and
discussions with Citibank on reversals and
Appendix B
1.4 7 Apr 2004 Updated following series of clarifications
1.5 12 May 2004 I Updated following clarification from Citibank
1.6 17 Aug 2004 I Updated with latest agreed changes
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Version Date Reason for Issue Associated
WP / CT
2.0 08 Oct 2004 Issued for Sign-off
Table 2: Document History
1.3 Change Process
Any changes to this issued version of this document will be made, controlled and distributed by: -
David Gray via Post Office Document Management
[IT.Controlled.Document.Revie'
1.4 Review Details
Review
Comments by :
Review
Comments to :
Mandatory Review Authority Name
Post Office Ltd Beverley Dunn, David Gray
Fujitsu Services Ltd
Technical Design Authority Stephen Probert
Design Authority David Johns
Development Mgr Mark Taylor
Development & Test Director Alan d'Alvarez
Test Design Janusz Holender
CitiBank Ed Koslow
EDS Steve Leek
Optional Review / Issued for Information
Post Office Ltd Bob Booth, Marc Reardon, Jason Slatcher
Fujitsu Services Ltd
Release Manager Gill Jackson
Design Chris Bailey, Mark Jarosz,
Tom Northcott, Nasser Siddiqi, Phil Turner,
Simon Fawkes, Alex Robinson
Development Team Leader Peter Ambrose
Development Anne Mohan, John Rayner,
Test Debbie Richardson, Hermia Figueiredo,
Stephen Newman
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CitiBank John Ibbitson
EDS Keith Peers
1.5 Changes in this Version
Version Changes
2.0 Change to Currency Code, Transaction (bitmap ref. 049) for PIN Change — now
optional. This affects sections 4.1.2, 4.2.3, 4.2.6
Change to handling of AWK to specifically use Atalla variant 1. This affects sections 1.7
(ATCRM), 4.1.2 (Network Management Information), 4.2.10.1 (Network Management
Information), and 6.1.
1.6 Change of author.
Section 1.1 — Change of Horizon release to S75; Amplification of title; Change to Fujitsu
Services’ Supplier Distribution.
Sections 3.2 and 4.2.9.1 and 5.1 — Administration Advice messages will not be
generated by CAPO but will be correctly handled upon receipt by NBX.
Section 4.1.2 — Advice / Reversal Reason Code: deleted “Reserved private”; Retrieval
Reference Number: added uniqueness statement “It will be unique for a terminal ID, at
least within 10 years”, as this is controlled by NBX.
Section 4.2.7.1 — Replaced “duplicate [E1]” by “duplicate 0420"; Moved definition of
0420 up so that it now appears before this use of it.
Section 4.2.7.2 — Date, Settlement: Replaced “Copied from the [A1]” by “Copied from
the “[R3]” {these are tantamount to the same, as that in the [A1] has been echoed from
the [R3], but the new description describes the NBX behaviour}.
Section 4.2.10 — Replaced sentence on use of Handshakes by a cross-reference to the
TIS.
Section 5.2: Added statement on binary Bit Maps as existing statement is easily
overlooked; Added statement on interleaving and request during key change.
Appendix B — Added clarification on value of Transaction Amount (tag 9F02) in ICC
Data.
Minor formatting changes
1.5 Section 5.1 updated to state that CAPO will not validate transmission date and time
against the date and time that messages are received
1.4 Document ref. inserted in header; standard terminology (Log On/Off for Sign On /Off
and Handshake for Echo Test); Section 1.7 — document references updated; Section
4.1.2 — table sorted to alphabetic sequence, note in Message Security Code (096),
Network Management Information (125) check value size corrected; Section 4.2.2.2 —
Processing Code for Withdrawal with Balance corrected to 010000; Section 4.2.7.1 —
provision for Reversal Requests up to 5 days; Section 4.2.7.2 - entry in Note column for
fields 003 and 015; Section 4.2.10 - Handshake messages whether logged on or not;
Section 5.2 renumbered; Section 6.4 — clarification of daily AWK change; Section 9 —
under ‘Description’ remove (055) being present in all ICC Reversal Requests
1.3 General — removal of reference to NBE Functional Solution Definition and minor textual
changes.
Section 1.7 - Update Refs. [2, 3], insert new document “NBX Business Parameters”
(Ref. [7]); section 4.1.1 — removal of references to binary representation of data; section
4.1.2 — removal of “PO” from Card Acceptor Name, ICC Data field defined as
hexadecimal, Retrieval Reference Number redefined; sections 4.2.7.1, 4.2.8.1 and 5.1
— insertion of conditions under which a transaction is reversed; Appendix A — corrected
cross reference (Ref. [3]); Appendix B revised.
Table 3: Changes in this Version
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1.6 Key Contacts
Name
Position
Phone Number
Bob Booth
Solutions Architect
0.
Table 4: Key Contacts
1.7 Associated Documents
Reference Version I Date Title Source
1. I 1S08583:1987(E) Aug 1987 I Bank Card Originated Messages Iso
2. I SU/PLA/016 0.3 NBX Volume Model Comparisons Post Office
3. I NB/IFS/031 Horizon — Card Account Mapping Post Office
4. I NB/IFS/030 NBX — FI Reconciliation and Post Office
Settlement File Format AIS
5. I NB/IFS/027 NBX — POCA Technical Interface Post Office
Specification (TIS)
6. I NB/OLA/O01 Horizon — EDS Operational Level Post Office
Agreement
7. I NB/IFS/035 NBX Business Parameters Post Office
ATCRM 424645- I July 2003 I Atalla Banking Command Hewlett
002 Reference Manual Packard
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 5: Associated Documents
Version 2.0
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Table of Contents
1 DOCUMENT CONTROL 2
1.1. Document Information 2
1.2 Document History 2
1.3. Change Process =
1.4 Review Details 3
1.5. Changes in this Version 4
1.6 Key Contacts 5
1.7 Associated Documents 5
2 INTRODUCTION 8
21 Purpose 8
2.2 Scope 8
2.3 Structure 8
2.4 Terms and Abbreviations 8
3 OVERVIEW OF THE INTERFACE 9
3.1 Data Description 9
3.2 Derivation and Use of Data 1
3.3. Non Computer Data 12
4 DATAITEMS 13
4.1 Data Item List 13
4.1.1 General Message Element Definitions and Abbreviations 13
44 Messages Data Elements 15
4.2 Data Interpretations 24
4.21 [R3] - Balance Enquiry 25
4.2.2 [R3] - Financial Transaction Request 26
4.2.3 [R3]- PIN Change 28
4.2.4 [A1]- Balance Enquiry Response 29
4.2.5 [A1]- Financial Transaction Response 30
4.2.6 [A1]- PIN Change Response 31
4.2.7 [E1]- Reversal Request 32
4.2.8 [E2] - Reversal Request Response 34
4.2.9 Administration Advice (0620) 35
4.2.10 Network Management Messages (0800 / 0810) 36
4.2.11 REC —NBX Reconciliation File Format 37
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5 TRANSFER STRUCTURE 38
5.1 Transfer Grouping 38
5.2 Transfer Structure 39
5.3 Record Structure 39
5.4 Sequences 39
5.5 Data Volumes 39
5.6 Data Authentication 39
5.7. Data Dictionary 39
6 SECURITY OF TRANSMITTED DATA 40
6.1 Protected Data 40
6.2. Encryption and Decryption Methods 40
6.3. Session Establishment 40
6.4 Key Management 40
6.4.1 Acquirer Working Key Distribution 42
7 OPERATIONAL PROCEDURES 45
7.1 Processing Cycles 45
7.2 Security Procedures 45
7.3 Fallback Procedures 45
7.4 Control 45
8 APPENDIXA 46
8.1 Response Codes 46
8.2 Reversal Reason Codes 47
9 APPENDIX B 48
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2 Introduction
2.1 Purpose
The purpose of this document is:
* To specify the interface between the NBX and CAPO systems using ISO 8583 (1987), [Ref. 1].
¢ To provide the development teams with sufficient detail to develop the NBX - CAPO interface.
* To provide a consistent communications vehicle amongst the development teams who have
responsibility for developing the various components comprising the application.
2.2 Scope
This document applies to the interface between the NBX and CAPO only. It includes only those financial
transaction messages and network messages sufficient to support the financial services being delivered by
CAPO via the NBX.
2.3 Structure
Section 3 contains a high level overview of the NBX — CAPO 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 ISO 8583 (1987), [Ref. 1].
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.
2.4 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 - CAPO interface:
NBX Description Direction
Message ID
[R3] Authorisation / Financial Transaction Request: NBX > CAPO
* Balance Enquiry (0100)
« Withdrawal with Balance (0200)
e Withdraw Limit (0200). Also sometimes referred
to as “Withdraw All’.
* PIN Change (0100)
[A1] Authorisation/Financial Transaction Request CAPO > NBX
Response:
e Balance Enquiry Response (0110)
e Withdrawal with Balance Response (0210)
e Withdraw Limit Response (0210)
e PIN Change Response (0110)
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 > CAPO
e Acquirer Reversal Request (0420)
e Acquirer Reversal Request Repeat (0421)
[E2] Acquirer Reversal Request Response Message CAPO > NBX
(0430)
0500/0510 Reconciliation control messages NBX > CAPO
These messages are to be excluded. CAPO > NBX
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NBX Description Direction
Message ID
0620 Administration Advice (0620) NBX > CAPO
Administration Advice messages (0620) are sent CAPO > NBX
to/from CAPO when a received message cannot be
de-blocked, in order to initiate manual investigation of
a problem by either CAPO or the NBX
0800 Network Management Request (0800):
e Handshake (also known as Echo tests) 3
e Logon / Logoff (also known as Sign on / Sign off) we > a
e Security Key Change
0810 Network Management Request Response (0810) CAPO > NBX
REC Reconciliation File NBX > CAPO
(The REC settlement file and the conditions under
which it is sent from the NBX to CAPO are addressed
in the NBX — FI Reconciliation and Settlement, [Ref.
4]. )
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3.2 Derivation and Use of Data
The messages listed in section 3.1 are generally exchanged as a result of a transaction initiated either by a
clerk at a Post Office outlet or by CAPO. 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 CAPO in
terms of the received message that causes each NBX - CAPO message to be exchanged, and the transmitted
message resulting from the NBX - CAPO message exchange:
Message Sequence
Horizon Horizon NBX CAPO
Outlet Campus
[R1]> [R2] > 0100/0200
[R3] >
< [A3] < [A2] <
0110/0210
[At]
[Co] > Expedi 0420/0421
ted [E1]>
[C2] >
< 0430
{E2]
The messages exchanged over this interface relating to reconciliation and settlement are initiated by the NBX.
Security key exchange messages are initiated by the NBX and acknowledged by CAPO. The NBX will send a
new working key, for each of its Pls, to CAPO at least once in every 24-hour period. The business processes
with respect to these messages are addressed in section 6.4. The following table shows a high-level
description of the security messages exchanged between CAPO and the NBX. The full list of 0800 messages
initiated by the NBX, and acknowledged by a 0810 response from CAPO, can be found in section 4.2.10.
Message Sequence
Horizon Horizon NBX CAPO
Outlet Campus
0800 (Logon >
074)
0810
Lit
0800 (Key
Change -
Acquirer
Zone code
161)
0810
+
0800 (Key >
Change -
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Message Sequence
Horizon Horizon NBX CAPO
Outlet Campus
Acquirer
zone code
161)
< 0810
Logoff messages are initiated by the NBX and acknowledged by CAPO, as shown in the following table.
Message Sequence
Horizon Horizon NBX CAPO
Outlet Campus
0800 (Logoff >
072)
< 0810
Handshake messages are initiated by the NBX and acknowledged by CAPO, as shown in the following table.
Message Sequence
Horizon Horizon NBX CAPO
Outlet Campus
0800 >
(Handshake
361)
< 0810
Administration Advice messages are sent from NBX to CAPO when a received message cannot be deblocked
or when a message fails syntax checking, in order to initiate manual investigation of a problem by either CAPO.
or the NBX. CAPO will not generate Administration Advice messages, but NBX will correctly handle their
receipt. The following table shows the possible message flows.
Message Sequence
Horizon Horizon NBX CAPO
Outlet Campus
XXXX_
+t
0620
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)
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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 CAPO 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 and attribute of each data element (DE) and Data Sub-elements
are shown in the following table (taken from ISO 8583 (1987), [Ref. 1]):
Notation IExplanation
la [Alphabetic characters only (mixed case)
In Numeric Digits onh
is Special characters
lan [Alphabetic (mixed case) or Numeric characters
jas Alphabetic (mixed case) or Special characters
Ins Numeric or Special characters
ans Alphabetic (mixed case), Numeric or Special characters only
IDD Day
MM. Month
YY Year
hh Hour
mm Minutes
Iss 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.
Ih hexadecimal representation of the data
iz track 2 data as defined by ISO 7811 and ISO 7813
x. Sign — C (credit) or D (debit)
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.
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The “Description” column contains a brief description of the field, as used in the messages defined in this AIS,
together with any additional comments.
CAPO will operate in Mixed case, and will not validate the Alphabetic characters for case in any field.
However, where data is echoed or copied in messages, the echoed/copied fields should be in the same case
as the original field.
The POCA Servers and the NBX Servers both use the ASCII English character set (CCSID = 437).
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4.1.2 Messages Data Elements
The ISO 8583 (1987) Data Elements exchanged within messages over this interface are listed below. A fuller description is given in the ISO 8583 (1987)
Standard, [Ref. 1]. Note that data elements pertaining to the tertiary bitmap are not used on this interface.
JAccount Identification 1 I 102 ans I ...28 Not used by NBX
JAccount Identification 2 I 103 ans I ..28 Not used by NBX
lAcquiring Institution 019 n 3 Not required for NBX transactions
Country Code
JAcquiring Institution 032 I LLVAR] on .. 11 I NBX from ICode identifying the Acquirer (Post Office Limited), set to
Identification Code Ref Data I2200040000
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JAdditional Amounts o The Ledger and Available balances if the request was.
lauthorised (Response Code=00), or declined because of
insufficient funds (Response Code=51), in the following
Hormat:
IAccount Type (n2) = 00 (Funding (default) account)
Amount Type (n2) = 01 (Account ledger balance)
Currency Code (n3) = 826 (GB Pounds) or 978 (Euros)
Amount (x+n12), where x = 0, C (Credit amount) or D
(Debit amount)
IAccount Type (n2) = 00 (Funding (default) account)
IAmount Type (n2) = 02 (Account available balance)
ICurrency Code (n3) = 826 (GB Pounds) or 978 (Euros)
Amount (x+n12), where x = 0, C (Credit amount) or D
(Debit amount)
Not required for PIN Change transaction.
This usage of the field is an extension to the base ISO
18583(1987) standard, [Ref. 1].
IAdditional Response Data I 044 I LLVAR an . 25 Bank Mandatory if Response Code=30. Positions 1-3 are the bit c c c
Inumber of the field in error.
This usage of the field is an extension to the base ISO
18583(1987) standard, (Ref. 1]
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1S0 8583 (1987) Data [Bitmap] Format IAttributeI Field I Source IDescription Required
Element Ref. Size
tra} ] (Ra ] tat I atl I t€11 I t€21 I 0620 I 0800 ] 0810
0100 I 0200} 0110 I o2t0 I 0420 I 0430
10421
lAdvice / Reversal Reason I 060 [LLLVARI an 9 I NBX [This field will only be used for reversal reason, M
Cod
ode Bytes 1-2 will always be set to 80
Bytes 3-4 will be used to give a meaningful reason for the
reversal. See Appendix A for the list of Reversal Reason
Codes.
‘The remaining bytes will not be transmitted.
This usage of the field is an extension to the base ISO
18583(1987) standard, [Ref. 1]
JAmount, Cardholder Billing I 008 n 8 Not required.
Fee
lAmount, Settlement (005 n 12 Not required
lAmount, Transaction 004 n 12. I Clerk at [Decimal amount in smallest unit of the specified currency M uw ]™M I
Outlet I(ie. GBP pence or EUR cents)
Not required for Balance Enquiry or PIN Change
For Withdraw Limit, this will be set to the Product Limit,
passed by Horizon in the Maximum Withdrawal message
jelement.
JAmount, Transaction Fee I 028 I xtné I an 9 Not required
lamount, Transaction 030 I x8 I an 9 Bank [Used to indicate the fee charged by CAPO. If no fee is to Te
Processing Fee be charged, the field will be set to zero,
‘This usage of the field is an extension to the base ISO.
18583(1987) standard, [Ref. 1]
JApproval Code Length I 027 D 1 Not required.
JAuthorisation Identification I 038 an 6 CAPO will issue an authorisation number for every u [uf
Response transaction processed, and will want it returned in
(0420/0421 processing requests
JAuthorisation Identification I 027 a 1 Not required as the Authorisation Identification Response
Response Length length is to always be set to 6 characters.
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ISO 8583 (1987) Data [Bitmap] Format IAttribute} Field I Source IDescription Required
Element Ref. Size
IR3] I [R3] I At] I [At] I [E41 I [€2] I 0620 I 0800 I o810
0100 I 0200} 0110 I 0210 I 0420 I 0430
10421
Card Acceptor Name / 043 ans 40 I NBX from IFirst 40 characters of outlet address in format: mi M
Location Ref Data I01-23 first 23 characters of Name and Address
(= first 23 chars of ADDRESS 1)
[24-36 first 13 characters of City
(= first 13 characters of ADDRESS 4)
37-38 spaces
39-40 spaces
Card Acceptor Terminal I 041 ans 8 Outlet [Comprises 6 digit outlet id (group_id) + 2 digit terminal id I mM I mM I M mM I M I
Identification from I(node_id)
system
Card Sequence Number I 023 n 3 Not required.
Conversion Rate, 009 n 8 Not required.
Settlement
Currency Code, 050 an 5 Not required.
Settlement
Currency Code, 049 an 3 I Clerk at JOnly 826 (GBP) will be accepted by CAPO initially. NBX I wo] mM ImcIm I mM IM
Transaction outlet will translate GBP code received from Horizon to 826
(using ISO 4217 standard) for CAPO. Other values (e.g.
1978/EUR) may be added to Currency Code CPF Table if
required at a later date, and will be translated in the same
lway.
Date, Conversion 016 n 4 Not required.
Date, Expiration 014 n 4 Not required.
Date, Local Transaction I 013 I MMDD I n 4 Outlet IAs printed on receipt, transaction request date in Local MiM/oM mM I M I
from ITime.
System
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1S0 8583 (1987) Data [Bitmap] Format IAttributeI Field I Source IDescription Required
Element Ref. Size
tra} ] (Ra ] tat I atl I t€11 I t€21 I 0620 I 0800 ] 0810
0100 I 0200} 0110 I o2t0 I 0420 I 0430
10421
Date, Settlement 015 I MMDD n 4 NBX NBX always set the Settlement Date. Set to system date if M M M M
before settlement cutover time (from Ref Data), or system
date +1 if after settlement cutover time
This usage of the field is an extension to the base ISO.
8583(1987) standard, [Ref. 1]
Forwarding Institution 021 n 3 Not required.
Country Code
Forwarding Institution 033 n 1 Not required, since NBX is an Acquirer
Identification Code
ICC Data 055 h 510 Mandatory where point of service entry mode (bit 022), tc I ce
digits 1 and 2 = 05
ICC Data elements for this bit field are in Appendix B.
Info Text 124 ILLLVARI ans 255 I Sender IContains the first 255 bytes of the message rejected by the M
sender (either NBX or CAPO).
This usage of the field is an extension to the base ISO
18583(1987) standard, (Ref. 1]
Message Security Code I 096 an 8 I Sender IPassword to network management requests c
Required for key change, logon and logoff
Note ~ Not used by CAPO
Network International 024 n 3 Not required.
identifier
‘ Conditional on ICC point of service
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1SO 8583 (1987) Data [Bitmap] Format [Attribute] Field I Source IDescription Required
Element Ref. Size
1R3] I (R3}] (At) I tat} I (1) I E21 I 0620 I 0800 I o810
0100 }0200} 0110 I 0210 I 0420 I 0430
10421
Network Management 125 ILLLVARI ans 60 Sender Additional information required for key change and c
Information verification. Positions 01-32=32 byte working key
(encrypted under the Acquirer Zone Master Key using
IAtalla variant 1), 33-36=check value (4 bytes), 37-38 check
value padding (zeroes),39-60 Spaces (optional).
[Note - 4 byte check value used because Atalla only
returns 4 bytes)
This usage of the field is an extension to the base ISO
18583(1987) standard, [Ref. 1]
Network Management 070 n 3 ICodes to be used for 0800/0810 messages are defined in ve
Information Code section 4.2.10
New PIN (Reserved for I 423 ILLLVARI ans 999 I Customer IThis field will be used to hold the Customer choice of new I C
Private Use) at Outlet IPIN on PIN Change. Positions 1-2 set to Authorization
Type=NP, positions 3-18 set to the new PIN (encrypted
lusing ISO 9564-1 Format 0 as defined in ANSI X9.8).
This usage of the field is an extension to the base ISO
{8583(1987) standard, [Ref. 1]
Original Data Elements 090 n 42 NBX [Set by NBX to be a concatenation of the following five data M M
elements from the original 0100/0200 message:
Message Type Identifier (n4),
[Systems Trace Audit Number (n6),
Transmission Date and Time (n10),
[Acquiring Institution Identification Code (n11),,
Forwarding Institution Identification Code (n11, and set to
100000000000 for CAPO)
Personal Identification 052 h 16 Outlet ICustomer PIN Entered by customer & encrypted using ISO] M I M
Number (PIN) Data. from — I9564-1 Format 0 as defined in ANSI X9.8
customer
This usage of the field is an extension to the base ISO
18583(1987) standard, [Ref. 1]
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ISO 8583 (1987) Data IBitmapI Format IAttributeI Field I Source IDescription Required
Element Ref. Size
1R3] I (3 } fat] I fat] I fE4] I (2) I 0620 I 0800 I 0810
0100 I 0200} 0110 I 0210 I 0420 I 0430
10424
Point of Service Condition I 025 n 2 Outlet IThe value should initially always be 00. mu [ulm vu I u [o™
code
Point of Service Data 061 ans 20 Notrequired
Point of Service Entry 022 n 3 Outlet [Digits 1-2 will be: MM M
Mode from
system [01 (Manual entry) or
J05 (ICC entry (including track 2 read and transmitted)) or
190 (Mag Stripe, Track 2 read and fully transmitted)
Digit 3= 1 (PIN entry capability)
Point of Service PIN 026 n 2 Not appropriate to messages passed on this interface -
Capture Code POS Transactions Only
Primary Account Number I 002 I LLVARI n 19. I System or [Either extracted from Track 2 data or entered manually. mu {ulm mu I oM
Clerk at
Outlet
Primary Account Number, I 034 ns 28 Not required.
Extended
Primary Account Number I 020 n 3 Not required - foreign currency transactions are not
Extended, Country Code supported by NBX
Processing Code 003 n 6 NBX [Derived by NBX from Txn_type passed by Horizon. NBX I M I M I M mu I mM [om
lwill set digits 1 and 2 to 07 for Withdrawal with Balance, 91
Hor Withdraw Limit, 90 for PIN Change and 31 for Balance
Enquiry. Digits 3 to 6 will be set to zero (default). All 6
digits passed by NBX and CAPO.
Receiving Institution 068 n 3 Not required - foreign currency transactions are not
Country Code supported by NBX
Receiving Institution 400 n 4 Not required.
Identification Code
Response Code 039 an 2 ICode indicating transaction step outcome. Source M M M M
Jdependent on transaction type. See Appendix A for the list
lof Response Codes
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ISO 8583 (1987) Data IBitmapI Format I Attribute} Field Source IDescription Required
Element Ref. Size
1R3] I (3 } fat] I fat] I fE4] I (2) I 0620 I 0800 I 0810
0100 I 0200} 0110 I 0210 I 0420 I 0430
10424
Retrieval Reference 037 an 12 NBX Additional transaction identifier, assigned by NBX. It willbe] M I M M M M M
Number lunique for a terminal ID, at least within 10 years.
Bytes 01-04 set to date (YDDD)
Byte 05 set to value A or B (upper or lower case) to record
lwhich of two agents processed the message (the case
differentiates between instances of the agent)
Digit 06 set to value 0 through 3 (being agent hash value
lused in routing transactions)
Digits 07-12 set to a 6-digit cycling number generated at
leach counter
[Systems Trace Audit ott n 6 NBX [Transaction identifier, assigned by NBX within the request,I M I M I M uv [mu f[u iu [uM]
Number land included in all subsequent messages relating to that
transaction ({A1] response and [E1] / [E2] reversal
messages)
The STAN is a 6 digit numeric field 0 to 999999. Each PI
manages its own STAN which increments by one to
provide a sequential identifier for each message. The
STAN may cycle within the day but will be unique within
the period of the NBX PI context fle.
EBT does not use this field directly, but it is used by
Citibank’s back office operations’ tracking systems
IGaps in the STAN sequence have no significance (and
thus will not cause alerts in EBT)
Time, Local Transaction I 012 IhhmmssI n 6 Outlet As printed on receipt, transaction request time in Local uiu]u [uM [ut
from {Time
System
‘Transmission Date and I 007 IMMDDhI n 10 I Sender IDate and time of transmission of the message (notcaried I M I MI mM I mM [mu [mMI[mM [mui]
Time hmmss Htorward from previous messages)
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Outlet Mandatory if track 2 data available (card successfully
from card Iswiped or ICC processed).
‘Track 2 data does not include the start/end sentinels nor
the LRC (longitudinal redundancy check)
This usage of the field is an extension to the base ISO
18583(1987) standard, [Ref. 1].
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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, and relate to the list in Section 4.1.2.
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
Cc 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.
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.
Where Message Elements exist in the IS08583 standard (1987 Version), [Ref. 1] as either Mandatory or
Conditional, but are not required for the CAPO interface, they have been included in the message definition
tables, but have been shaded out and labelled as “Not required”.
Itis essential that developers of this interface also refer to ISO 8583 (1987), [Ref. 1] and the Horizon — Card
Account Mapping, [Ref. 3] for further details of data derivation and use. The message definitions do not
explicitly show the bitmaps as individual message elements, because they are an essential part of the ISO.
8583 (1987) transfer structure. However, all messages passed over this interface will include bitmap 1.
Bitmaps will be formatted as binary.
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4.2.1 [R3] - Balance Enquiry
4.2.1.1 Overview
This message is sent by the NBX to CAPO. The message requests a Balance Enquiry transaction.
The [R3] Balance Enquiry message maps to the following ISO message:
e 0100 — Authorisation Request
4.2.1.2 Message Definition
Message Element Bitmap Required I Notes/ Conditions
Reference
Primary Account Number 002 M
Processing Code 003 310000 for Balance Enquiry.
‘Amount, Transaction 004 Not required.
Transmission Date and Time 007 M
‘Systems Trace Audit Number 011 M
Time, Local Transaction 012 M
Date, Local Transaction 013 M
Date, Expiration 014 Not required.
‘Acquiring Institution Country Code 019 Not required.
Primary Account Number Extended, 020 Not required.
Country Code
Forwarding Institution Country Code 021 Not required.
Point of Service Entry Mode 022 M
Card Sequence Number 023 Not required.
Point of Service Condition Code 025 M
Point of Service PIN capture code 026 Not required.
‘Approval Code Length 027 Not required.
Amount Transaction Fee 028 Not required.
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required.
Code
Primary Account Number, Extended 034 Not required.
Track-2 Data 035 c Mandatory if track data is available (ICC processed
or card successfully swiped),
Retrieval Reference Number 037 M
Card Acceptor Terminal 041 M
Identification
Card Acceptor Name / Location 043 M
Currency Code, Transaction 049 M
Personal Identification Number (PIN) 052 M
Data
ICC Data 055 c Mandatory if ICC processed
Point of Service Data 061 Not required.
Receiving Institution Country Code 068 Not required,
Receiving Institution Identification 100 Not required.
Code
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4.2.2 [R3] - Financial Transaction Request
4.2.2.1 Overview
This message is sent by the NBX to CAPO. The message requests a financial transaction of one of
the following types:
¢ Withdrawal with Balance.
¢ Withdraw Limit.
The [R3] Financial Transaction Request message maps to the following ISO message:
e 0200 - Financial Transaction Request.
4.2.2.2 Message Definition
Message Element Bitmap Required I Notes/ Conditions
Reference
Primary Account Number 002 M
Processing Code 003 M 070000 for Withdrawal with Balance.
910000 for Withdraw Limit.
‘Amount, Transaction 004 M Requested Amount for ‘Withdrawal with Balance”.
For “Withdraw Limit’, this will be set to the Product
Limit.
Amount, Settlement 005, Not required.
Transmission Date and Time 007 M
Conversion Rate, Settlement 009 Not required,
‘Systems Trace Audit Number 011 M
Time, Local Transaction 012 M
Date, Local Transaction 013 M
Date, Expiration 014 Not required.
Date, Settlement 015 M
Date, Conversion 016 Not required.
‘Acquiring Institution Country Code 019 Not required,
Primary Account Number Extended, 020 Not required.
Country Code
Forwarding Institution Country Code 021 Not required.
Point of Service Entry Mode 022 M
Card Sequence Number 023 Not required,
Point of Service Condition Code. 025 M
Point of Service PIN Capture Code 026 Not required.
Authorisation Identification 027 Not required.
Response Length
Amount, Transaction Fee 028 Not required.
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required.
Code
Primary Account Number, Extended 034 Not required.
Track-2 Data 035 Cc Mandatory if track data is available (ICC processed
or card successfully swiped)
Retrieval Reference Number 037 M
Response Code 039 Not required.
Card Acceptor Terminal 047 M
Identification
Card Acceptor Name / Location 043 M
Currency Code, Transaction 049 M
Currency Code, Settlement 050 Not required.
Personal Identification Number (PIN) 052 M
Data
ICC Data 055 c Mandatory if ICC processed
Point of Service Data 061
Receiving Institution Country Code 068. Not required.
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Message Element Bitmap Required I Notes / Conditions
Reference
Receiving Institution Identification 100 Not required,
Code
‘Account Identification 1 102 Not required,
‘Account Identification 2 103 Not required.
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4.2.3 [R3] - PIN Change
4.2.3.1 Overview
This message is sent by the NBX to CAPO. The message requests a PIN Change transaction.
The [R3] PIN Change message maps to the following ISO message:
« 0100 — Authorisation Request.
4.2.3.2 Message Definition
Message Element Bitmap Required I Notes/ Conditions
Reference
Primary Account Number 002 M
Processing Code 003 M ‘900000 for PIN Change
Amount, Transaction 004 Not required.
Transmission Date and Time 007 M
Systems Trace Audit Number 011 M
Time, Local Transaction 012 M
Date, Local Transaction 013 M
Date, Expiration 014 Not required.
‘Acquiring Institution Country Code 019 Not required,
Primary Account Number Extended, 020 Not required.
Country Code
Forwarding Institution Country Code 021 Not required.
Point of Service Entry Mode 022 M
Card Sequence Number 023 Not required.
Point of Service Condition Code. 025 M
Point of Service PIN capture code 026 Not required.
‘Approval Code Length 027 Not required.
Amount, Transaction Fee 028 Not required.
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required.
Code
Primary Account Number, Extended 034 Not required.
Track-2 Data 035 c Mandatory if track 2 data is available (ICC processed
or card successfully swiped).
Retrieval Reference Number 037 M
Card Acceptor Terminal 041 M
Identification
Card Acceptor Name / Location 043 M
Currency Code, Transaction 049 (e) Omitted by NBX.
Personal Identification Number (PIN) 052 M The “old” PIN
Data
ICC Data 055 Cc Mandatory if ICC processed
Point of Service Data 061
Receiving Institution Country Code 068 Not required.
Receiving Institution Identification 100 Not required,
Code
New PIN (Reserved for Private Use) 123 M The “new” PIN.
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4.2.4 [A1] - Balance Enquiry Response
4.2.4.1 Overview
This message is sent by CAPO to the NBX. The message contains a Balance Enquiry request
response.
The [A1] Balance Enquiry Response message maps to the following ISO message:
e 0110 - Authorisation Request Response.
4.2.4.2 Message Definition
Message Element Bitmap Required I Notes / Conditions
Reference
Primary Account Number 002 M Echoed from the request message.
Processing Code 003 M Echoed from the request message.
‘Amount, Transaction 004 Not required.
Transmission Date and Time 007 M
Systems Trace Audit Number O17 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.
‘Acquiring Institution Country Code 019 Not required,
Primary Account Number Extended, 020 Not required,
Country Code
Forwarding Institution Country Code. 027 Not required,
Network International Identifier 024 Not required,
Point of Service Condition Code 025 M Echoed from the request message.
‘Amount, Transaction Processing 030 M
Fee
‘Acquiring Institution Identification 032 M Echoed from the request message.
Code
Forwarding Institution Identification 033 Not required,
Code
Primary Account Number, Extended 034 Not required,
Retrieval Reference Number 037 M Echoed from the request message.
Authorisation Identification 038 M
Response
Response Code 039 M
Card Acceptor Terminal 041 M Echoed from the request message.
Identification
Additional Response Data 044 Cc Mandatory if Response Code=30 (field in error)
Currency Code, Transaction 049 M
‘Additional Amounts 054 Cc The Available and Ledger balances if request was
successful.
Receiving Insfitution Country Code 068 Not required.
Receiving institution identification 100 Not required.
code
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4.2.5 [A1] - Financial Transaction Response
4.2.5.1 Overview
This message is sent by CAPO to the NBX. The message contains a Financial Transaction request
response.
The [A1] Financial Transaction Request Response message maps to the following ISO message:
e 0210 - Financial Transaction Request Response.
4.2.5.2 Message Definition
Message Element Bitmap Required I Notes / Conditions
Reference
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, except for an
approved “Withdraw Limit” transaction, where this
will be set to the amount authorised by CAPO
Amount, Settlement 005 Not required.
Transmission Date and Time 007 M
Conversion Rate, Settlement 009 Not required,
Systems Trace Audit Number O17 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 Echoed from the request message.
Date, Conversion 016 Not required.
Acquiring Institution Country Code 019 Not required.
Primary Account Number Extended, 020 Not required,
Country Code
Forwarding Institution Country Code 021 Not required,
Card Sequence Number 023 Not required,
Network International Identifier 024 Not required,
Point of Service Condition Code 025 M Echoed from the request message.
‘Amount, Transaction Processing 030 M
Fee
‘Acquiring Institution Identification 032 M Echoed from the request message.
Code
Forwarding Institution Identification 033 Not required.
Code
Primary Account Number, Extended 034 Not required,
Retrieval Reference Number. 037 M Echoed from the request message.
Authorisation Identification 038 M
Response
Response Code 039 M
Card Acceptor Terminal 047 M Echoed from the request message.
Identification
‘Additional Response Data 044 c Mandatory if Response Code=30 (field in error)
Currency Code, Transaction 049 M Echoed from the request message.
Currency Code, Settlement 050 Not required,
‘Additional Amounts 054 c The Available and Ledger balance information if the
request was authorised, or declined because of
insufficient funds.
Receiving Institution Identification 100 Not required,
Code
‘Account Identification 1 702 Not required,
‘Account Identification 2 103 Not required,
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4.2.6
4.2.6.1
4.2.6.2
Overview
[A1] - PIN Change Response
This message is sent by CAPO to the NBX. The message contains a PIN Change request response.
The [A1] PIN Change Response message maps to the following ISO message:
e« 0110 - Authorisation Request Response.
© Post Office™ 2004
Message Definition
Message Element Bitmap Required I Notes / Conditions
Reference
Primary Account Number 002 M Echoed from the request message.
Processing Code 003 M Echoed from the request message.
‘Amount, Transaction 004 Not required,
Transmission Date and Time 007 M
Systems Trace Audit Number O17 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.
‘Acquiring Institution Country Code O19 Not required,
Primary Account Number Extended, 020 Not required,
Country Code
Forwarding Institution Country Code 027 Not required.
Network International Identifier 024 Not required,
Point of Service Condition Code 025 M Echoed from the request message.
‘Amount, Transaction Processing 030 M
Fee
‘Acquiring Institution Identification 032 M Echoed from the request message.
Code
Forwarding Institution Identification 033 Not required.
Code
Primary Account Number, Extended 034 Not required.
Retrieval Reference Number 037 M Echoed from the request message.
Authorisation Identification 038 M
Response
Response Code 039 M
Card Acceptor Terminal 047 M Echoed from the request message.
Identification
Additional Response Data 044 c Mandatory if Response Code=30 (field in error)
Currency Code, Transaction 049 Cc Echoed from the request message if present.
Receiving Institution Country Code. 068 Not required,
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4.2.7 [E1] - Reversal Request
4.2.7.1 Overview
This message is sent by the NBX to CAPO when a financial transaction that has been processed by
the issuer needs to be reversed.
The [E1] message maps to the following ISO messages:
e 0420 - Reversal Request
e 0421 - Reversal Repeat.
Reversal [E1] messages are generated by the NBX. These are only sent to the FI to reverse a previously
authorised Accept transaction (i.e. [A1]) according to the following conditions:
e The Authorisation [A1] is late (i.e. is received after the Agent timeout period has been exceeded)
e The transaction outcome at the counter is different to the Authorisation response received at the
counter ([A3]) (e.g. clerk declines to proceed due to suspected fraud)
e The transaction outcome at the counter is indeterminate (e.g. counter has timed out waiting for
response, or ICC failed to complete any script processing)
Reversals [E1] can only be generated when the [A1] message to be reversed can be matched against a
[R3] request.
The NBX prevents duplicate 0420 messages being sent to the FI.
Reversal Requests may be sent up to a period, which shall be configurable and shall be set initially to
5 days, after the original transaction to which it refers.
Note that partial reversals are not supported over this interface. PIN Change reversals are also not
supported.
4.2.7.2 Message Definition
Message Element Bitmap Required I Notes/ Conditions
Reference
Primary Account Number 002 M
Processing Code 003 M Copied from the [AT]
Amount, Transaction 004 M
Amount, Settlement. 005, Not required.
Transmission Date and Time 007 M
Conversion Rate, Settlement 009 Not required,
‘Systems Trace Audit Number 011 M
Time, Local Transaction 0712 M
Date, Local Transaction 013 M
Date, Expiration 014 Not required.
Date, Settlement 015 M Copied from the [R3]
Date, Conversion 016 Not required.
Acquiring Institution Country Code 019 Not required,
Primary Account Number Extended, 020 Not required.
Country Code
Forwarding Institution Country Code 021 Not required.
Point of Service Entry Mode 022 M
Card Sequence Number 023 Not required,
Point Of Service Condition Code 025 M
Point Of Service PIN Capture Code. 026 Not required,
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Message Element Bitmap Required I Notes / Conditions
Reference
‘Amount Transaction Fee 028 Not required,
‘Amount, Transaction Processing 030 M
Fee
‘Acquiring Institution Identification 032 M
Code
Forwarding Institution Identification 033 Not required.
Code
Primary Account Number, Extended 034 Not required,
Track-2 Data 035 c Mandatory if track data is available (ICC processed
or card successfully swiped).
Retrieval Reference Number 037 M
Authorisation Identification 038 M
Response
Card Acceptor Terminal 047 M
Identification
Card Acceptor Name/Location 043 M
Currency Code, Transaction 049 M
Currency Code, Settlement 050 Not required.
Personal Identification Number (PIN) 052 Not required,
Data
ICC Data 055 May be present but is not required.
‘Advice/Reversal Reason Code 060 M
(Reserved Private)
Point of Service Data 067
Receiving Institution Country Code 068 Not required.
Original Data Elements 090 M
Replacement Amounts 095 Not required.
Receiving Institution Identification 100 Not required.
Code
Account Identification 1 102 Not required.
‘Account Identification 2 103 Not required,
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4.2.8 [E2] - Reversal Request Response
4.2.8.1 Overview
This message is sent by CAPO to the NBX in response to a reversal request from the NBX.
Reversal [E1] messages are “must deliver” messages. If an [E2] Reversal Response from the FI is not
received within a configurable period, a [E1] Reversal Repeat is sent subject to not exceeding a
configurable number of retries / elapsed time.
The [E2] message maps to the ISO message 0430 — Reversal Request Response.
4.2.8.2 Message Definition
Message Element Bitmap Required I Notes/ Conditions
Reference
Processing Code 003 M Echoed from the 042x message.
Amount, Transaction 004 M
Transmission Date and Time 007 M
Conversion Rate, Settlement 009 Not required.
Systems Trace Audit Number 17 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.
Date, Conversion 016 Not required.
Acquiring Institution Country Code 019 Not required.
Primary Account Number Extended, 020 Not required.
Country Code
Forwarding Institution Country Code 021 Not required.
Card Sequence Number 023 Not required
Network International Identifier 024 Not required,
Point of Service Condition Code. 025 M Echoed from the 042x message.
‘Amount, Transaction Fee 028 Not required,
Acquiring Institution Identification 032 M Echoed from the 042x message.
Code
Forwarding Institution Identification 033 Not required
Code
Primary Account Number, Extended. 034 Not required.
Retrieval Reference Number 037, M Echoed from the 042x message.
Response Code 039 M Will be set to either 00 — Approved, or 30 — Field in
error.
Card Acceptor Terminal 041 M Echoed from the 042x message.
Identification
‘Additional Response Data 044 c Mandatory if Response Code=30 (field in error)
Currency Code, Transaction 049 M Echoed from the 042x message.
Currency Code, Settlement 050 Not required.
Receiving Institution Country Code 068 Not required.
Original Data Elements 090 M Echoed from the 042x message.
Replacement Amounts 095 Not required
Receiving Institution Identification 100 Not required
Code
Account Identification 1 402 Not required
Account Identification 2 103 Not required.
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4.2.9 Administration Advice (0620)
4.2.9.1 Overview
Administration Advice messages are sent from NBX to CAPO when a received message cannot be
deblocked or when a message fails syntax checking, in order to initiate manual investigation of a
problem by either CAPO or the NBX. CAPO will not generate Administration Advice messages, but
NBX will correctly handle their receipt.
The Administration Advice message maps to ISO message 0620.
4.2.9.2 Message Definition
Message Element Bitmap Required I Notes / Conditions
Reference
Transmission Date and Time 007 M
Systems Trace Audit Number O17 M
Network Management Information 070 M Set to be 900
Code
Info Text 124 M
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4.2.10 Network Management Messages (0800 / 0810)
The following Network Management Messages will be exchanged between CAPO and the NBX:
e 0800 - Network Management Request Message
e 0810 - Network Management Response Message
They are used for the following purposes (followed by associated Network Management Information Code):
= Log on, initiated by NBX (071)
= Log off, initiated by NBX (072)
= Handshake, initiated by NBX (361)
= Key Change - Acquirer zone from NBX (161)
The conditions under which these messages, except for Handshakes, are sent for each of the specified
purposes are described in section 6.4. The use of Handshakes is described in the NBX — POCA Technical
Interface Specification, [Ref. 5].
4.2.10.1 Network Management Request (0800)
Message Element Bitmap Required] Notes/ Conditions
Reference
Transmission Date and Time 007 M
‘Systems Trace Audit Number oit M Set for this transaction
Network Management Information 070 M Values will depend on message purpose, as
Code described above
Message Security Code 096 Cc Required for key change, logon and logoff
Network Management Information 125 Cc Required for key change. Positions 01-32=32 byte
working key (encrypted under the Acquirer Zone
Master Key using Atalla variant 1), 33-38=check
value, 39-60 Spaces (optional)
4.2.10.2 Network Management Request Response (0810)
Message Element Bitmap I Required ) Notes / Conditions
Referen
ce
Transmission Date and Time 007 Mi
‘Systems Trace Audit Number om M Copied from the 0800,
Response Code 039 M
Network Management information Code_I 070 M This is copied from the 0800 received message.
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4.2.11. REC - NBX Reconciliation File Format
The REC reconciliation file, and the conditions under which it is sent to CAPO from the NBX are addressed in
the NBX — FI Reconciliation and Settlement File Format AIS, [Ref. 4]. The file transfer mechanism and
conditions of transfer are described in the NBX — POCA Technical Interface Specification, [Ref. 5].
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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 CAPO.
0420 0430
421 II 0620) I fea nee
4
A (a Co]
7
Horizon DRS POL
Campus Settlement
Gateway
Figure 1 - CAPO Message Flows in the Network Banking Environment
A 0620 message may be issued by the NBX in response to all messages from CAPO (for simplicity, only one
such flow is shown on the diagram). Note also that CAPO will not send 0620 messages to NBX; however, the
diagram shows that NBX will correctly process any that it receives.
Reversals (0420 messages) are not sent from NBX to CAPO unless and until an approved response (0210
message) has been received from CAPO.
In the event that NBX does not receive a reversal response within the allotted time interval then the NBX may
send EBT repeat reversals (0421 messages). CAPO will ensure that a reversal is not applied to an account
more than once.
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.
CAPO 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 — POCA Technical Interface Specification, [Ref. 5].
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5.2 Transfer Structure
The messages defined in this AIS will be exchanged in accordance with ISO 8583 (1987), [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 do not use the third bit map or any of its supported data elements.
Note also that the Bit Maps are transferred in binary.
Messages for one transaction may be interleaved with messages for any other transaction. Requests (0100
and 0200 messages) may continue to be sent during a key change, using the existing key until the Key
Change response has been received.
5.3 Record Structure
The record structure for the REC file passed over this interface is described in the NBX — Fl Reconciliation and
Settlement File Format AIS, [Ref. 4]. 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 CAPO. Further detail relating specifically to the NBX-CAPO connection can be
found in the NBX - POCA Technical Interface Specification (Ref. [5]). 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 within NBX Volume Model Comparisons, [Ref. 2].
5.6 Data Authentication
Message Authentication Codes (MACs) are not sent between CAPO and the NBX.
5.7 Data Dictionary
The Data Elements used on this interface are defined and described within ISO 8583 (1987), [Ref. 1].
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6 Security of Transmitted Data
The security standards for the NBX — CAPO interface are described in the NBX — POCA Technical Interface
Specification, [Ref. 5].
6.1 Protected Data
PIN blocks that pass across the interface from NBX to CAPO are encrypted under an Acquirer Working Key
(AWK). This key is used in the NBX - CAPO shared security zone. PIN Blocks encryption is translated from the
other security zone 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 (AWKs) are exchanged electronically encrypted under an Acquirer Zone Master Key
(AZMK) shared between NBX and CAPO. To facilitate import of the AWK into the CAPO systems, the AWK is
encrypted using Atalla variant 1 as defined in [ATCRM]. The AZMK is generated and owned by CAPO. The
AWK is owned and generated by the NBX.
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 CAPO as described in the NBX - POCA
Technical Interface Specification, [Ref. 5].
6.3 Session Establishment
Session Establishment will be initiated by the NBX. Initial Logon message exchanges are followed by
transmission of a new AWK by the NBX to CAPO, with a key check value protected by encryption under the
shared current AZMK.
CAPO verifies the key and acknowledges it to NBX. All PIN Block data is protected by this AWK until the
session ends or the AWK is renewed.
The only messages categorised as “must deliver” are Reversal Request (0420/0421).
6.4 Key Management
Key ownership is described in section 10 of the document Horizon — EDS Operational Level Agreement, [Ref.
6]. See also section 6.7 of the document NBX - POCA TIS, [Ref. 5]. NBX - CAPO Zone Management Keys are
managed in NBX.
CAPO:
e Generates three new AZMK components
« AZMK components will be generated in a secure manner
e Key components will contain
e Akey identifier (visible)
e Akey generation date (visible)
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e« Acomponent number (visible)
* 32 hex characters in two groups of sixteen characters — Triple DES key component, VISA method
e Four hex character Key Check Value, VISA method, printed securely and on separate sheet for the Key
Manager.
NBX:
e Manages secure logon of key holders & the key manager
e Accepts entry of key components & verifies component check digits
e Generates the AZMK from the key components & verifies the key check digits
Keys component documents must be stored and transported separately and securely.
The CAPO — NBX AZMK is renewed every six months by the process described above. The AZMK, having
been produced as described above, is securely transported to the NBX. The NBX and CAPO operations will
agree a time for key promotion. Promotion by both parties will be preceded by telephone coordination. After
promotion of the new AZMK the NBX operator will initiate an AWK exchange under the new AZMK using the
AWK Key Change sequence. This will provide online key verification of the AZMK. If this online key verification
procedure is successful the promoted AZMK will be confirmed as the current AZMK. If the AWK exchange is
unsuccessful manual procedures initiated by NBX and CAPO operators will revert to the old AZMK.
CAPO 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 two TCP/IP socket connections. A logical session will
be initiated by a logon, and data for that session will flow over both socket connections belonging to that PI
(see the NBX - POCA Technical Interface Specification, [Ref. 5] for further details). Each Pl generates a NBX
— CAPO Acquirer Working Key (AWK) which it sends to CAPO for validation. This AWK, if validated by CAPO,
is used by both socket connections between CAPO and the NBX PI that generated it. Logical sessions for a
different PI will use the AWK generated by that PI. All NBX Pls will protect their AWK in transit to CAPO 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).
e 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)
« Atsession initiation by NBX
e Onreceipt by CAPO of a 6" consecutive invalid PIN block on a session
e When an NBX operator requests a key change.
Work Load Distribution between the Pls will be performed by the NBX at the application level. To ensure that
the correct AWK is used, PIN block translation must occur after PI selection.
The Acquirer Zone Master Key is verified electronically after it has been transferred manually in component
form. The Acquirer Working Keys are exchanged and verified electronically. The network management
(0800/0810) messages used to perform these functions are described in detail in the following sections:
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6.4.1. Acquirer Working Key Distribution
NBX owns and generates AWKs. New AWks are distributed and verified electronically.
6.4.1.1 NBX Initiated Log On
1. Successful Log On
NBX CAPO
Logon —— 0800 (071) ———>
«<——— 0810 (071) ——_ OK (Response
Code 00 —
Completed
successfully)
Key Change ——— 0800 (161)
(AWK)
<——— 0810 (161) ————_ OK (Response
Code 00 —
Completed
successfully)
2. Bad AWK
NBX CAPO
Logon —— 0800 (071) ———
<——— 0810 (071) ————_ OK (Response
Code 00 —
Completed
successfully)
Key Change — 0800 (161) ———
(AWk) New Key
<—— 0810 (161) ————_ Denied
(Response
Code 76 — Key
synchronisation
error)
The NBX will resend the same AWK a configurable number of times
(currently set to 6). On the 6'" consecutive 76 code, the NBX will
generate and send a new AWK, and the retry count will be reset. In
the event of multiple key synchronization errors, NBX operations
should verify that the key management system and application
configuration parameters are correctly set for the current AZMK tag.
If no fault is found, NBX/CAPO operations should be contacted to
investigate the problem (e.g. establish whether the ZMK has just
been changed, whether either system has been restarted, when the
last successful message transfer was etc.).
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3. No response to AWK
NBX CAPO
Logon ———— 0800 (071) ———>
<——— 0810 (071) ————_ OK (Response
Code 00 —
Completed
successfully)
Key Change ——— 0800 (161) ———_>
(AWk)
No response
NBX will resend the message a configurable number of times
(currently set to 5). If there is still no response, NBX operations
should initiate investigation of the problem. e.g. If consultation
indicated a communication failure, Network Management should be
alerted.
6.4.1.2 Key Change due to PIN validation errors detected by CAPO
1. More than 5 consecutive PIN errors.
NBX CAPO
Business ——— 0100/0200»
message
<—— 0100/0200-—_ Error
(Response
Code 76 - Key
synchronisation
error)
(6" consecutive
occurrence)
Key Change ———. 0800 (161) ———_
(AWk)
<— 0810 (161) OK (Response
Code 00 —
Completed
successfully)
NBX will expedite the Key Change to minimise the number of
messages rejected due to PIN errors (code 76). In the event of an
unsuccessful Key Change, the PI should be stopped to allow
NBX/CAPO operations to investigate the problem.
6.4.1.3 Key Change NBX Operator request or 24hr use limit
1. Successful key change.
NBX CAPO
Key Change 0800 (161) ———>
(AWk)
<——— 0810 (161) OK (Response
Code 00 —
Completed
successfully)
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2. Bad AWK
NBX CAPO
Key Change — 0800 (161) ———>
(AWk)
<—— 0810 (161) ————_ Denied
(Response
Code 76 — Key
synchronisation
error)
The NBX will resend the same AWK a configurable number of times
(currently set to 6). On the 6" consecutive 76 code, the NBX will
generate and send a new AWK, and the retry count will be reset. In
the event of multiple key synchronization errors, NBX operations
should verify that the key management system and application
configuration parameters are correctly set for the current ZMK tag. If
no fault is found, NBX/CAPO operations should be contacted to
investigate the problem (e.g. establish whether the ZMK just been
changed, whether either system has been restarted, when the last
successful message transfer was etc.).
3. No response to AWK Request
NBX CAPO
Key Change — 0800 (161) ———>
(AWk)
No response
NBX will resend the message a configurable number of times
(currently set to 5). If there is still no response, NBX operations
should initiate investigation of the problem. e.g. If consultation
indicated a communication failure, Network Management should be
alerted.
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7 Operational Procedures
7.1 Processing Cycles
This interface relates to online and batch message exchange to support real time financial transactions, and to
the daily transmission to CAPO of the REC file.
Stale messages are logged and discarded before transmission or on receipt, as appropriate and no further
processing takes place.
The timeout associated with each message type is addressed in NBX Business Parameters, [Ref. 7].
“Must deliver” messages are retransmitted at parameter intervals until delivery is successful, as described in
NBX Business Parameters, [Ref. 7].
Transfer Initiation
All transfers defined in this AIS are automatic.
7.2 Security Procedures
Manual Procedures are required to support the above key management protocol, as described in Section 6
above.
7.3 Fallback Procedures
Fallback procedures are described in the NBX — POCA Technical Interface Specification, [Ref. 5]. 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, 0800 and 0810 messages awaiting transmission at the time of failure can safely be discarded,
as the integrity of the transaction is protected by timeouts. However, 0420 and 0421 ([E]) messages are to be
treated as “must deliver” and therefore must be transmitted on recovery.
7.4 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 CAPO 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
The response codes are defined in the document Horizon — Card Account Mapping, [Ref. 3].
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8.2 Reversal Reason Codes
The reasons that may be provided with Reversal Request [E1] messages sent by the NBX to CAPO are
defined in Horizon — Card Account Mapping [3].
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9 APPENDIX B
NBX-EBT Interface — ICC Data Field
Field 055 - ICC Data
Format
h.. 510
LLLVAR
Description
ICC Data (Field 055) is used to transport chip-specific data over the network. It will be present in all
authorisation requests, if POS Entry Mode (Field 022) indicates that the transaction was chip-initiated (value
Structure
Field 055 has its own generic structure and may contain one or more Private Data Sub-elements (PDSs), as
shown in the figure below.
"LLU 'VAR' - up to 510 bytes
one or more PDS occurrences
3 bytes 2 or 4 bytes 2 bytes variable length
pee PDS T PDS Length PDS Dat
Element ag eng aa
Length
Length Data Zone
Data Element Length specifies the total number of bytes in the Data Zone immediately following it.
Data Zone contains the ASCII representation of each hexadecimal digit (i.e. nibble) of the chip data to be
transferred; this comprises one or more PDS occurrences.
Each PDS corresponds to an EMV data element/object and comprises the following sub-fields.
PDS Tag 2 or 4 byte ‘tag’ value (ASCII hexadecimal), identifying the EMV data object contained in the
PDS. The second two bytes are present only if the first byte is odd ('1’, ‘3',.....'B', ‘D’, 'F')
and the second byte is 'F'.
PDS Length 2 bytes, specifying the length (in bytes) of the PDS Data immediately following it, expressed
as an ASCII representation of a decimal number (e.g. ‘12’ means the integer 12) in the
range 1 to 99.
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PDS Data Variable between 1 and 99 bytes, containing the actual data from the corresponding EMV
data object (as identified by the PDS Tag).
The PDS structure is referred to as Tag-Length-Value (TLV), as defined in the EMV standards.
Note that PDS's may appear in any order in Data Zone. The order shown in the table below corresponds to that
in which the relevant fields are input to the ARQC verification algorithm.
PDS's for Card Account
The PDS's required for Card Account transactions (passed in the NBX-EBT On-line Interface) are listed in the
following table. Note that the lengths shown in the table assume that all PDS Data is ASCII representation of
either hexadecimal digits, or decimal digits.
PDS Tag I Length I Comments
(Bytes)
Application Cryptogram 9F26 16 Contains an ARQC (ASCII hexadecimal)
Cryptogram Information Data QF27 2 ASCII hexadecimal
Transaction Amount 9FO02 12 Format n12 (ASCII numeric), set as follows:
« Requested Amount for Withdrawal with
Balance
¢ — Product Limit for Withdraw Limit
e — ‘000000000000' for Balance Enquiry and
PIN Change
Terminal Country Code 9F1A 4 Format n4 (ASCII numeric, set to ‘0826')
Terminal Verification Results (TVR) 95 10 ASCII hexadecimal
Transaction Currency Code 5F2A 4 Format n4 (ASCII numeric. 1** character
always ‘0')
Transaction Date 9A 6 Format n6 (ASCII numeric YYMMDD)
Transaction Type 9c 2 Format n2 (ASCII numeric)
Unpredictable Number 9F37 8 (ASCII hexadecimal)
Application Interchange Profile (AIP) 82 4 (ASCII hexadecimal)
Application Transaction Counter (ATC) I 9F36 4 (ASCII hexadecimal)
Issuer Application Data (IAD) 9F10 12 This PDS comprises the following:
* Derivation Key Index (2 bytes) (ASCII
numeric)
e Cryptogram Version Number (2 bytes)
(ASCII hexadecimal)
e Card Verification Results (CVR) (8 bytes)
(ASCII hexadecimal)
Maximum Total PDS Data length 84
The total length of Field 055 is 151 bytes, calculated as follows:
Field 055 Data Element Length 3
PDS Tags 40
PDS Lengths 24
PDS Data 84
Total 151
END OF DOCUMENT
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