FUJ00124016
FUJ00124016
Post Office Ltd
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9; Magistrates Court Act 1980, sub section, 5A(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Statement of: Gareth Idris JENKINS
Age ifunder 18: Over 18 (if over 18 insert ‘over 18°) Occupation: Business Architect
This statement (consisting of nine pages each signed by me) is true to the best of my knowledge and belief and I make
it knowing that, if it is tendered in evidence, I shall be liable to prosecution if I have wilfully stated in it anything which
T know to be false or do not believe true.
Dated the Sth day of October 2012
Signature
1. Introduction
Tam Gareth Idris Jenkins. I am employed by Fujitsu Services Ltd who have been contracted by Post Office
Lid to provide the Horizon systems operating in Post Offices around the country. However I understand
that my role is to assist the court rather than represent the views of my employers or Post Office Ltd.
I graduated from Cambridge University with a degree in Mathematics in 1973 and was awarded an MA by
Cambridge University in 1997. I was employed by ICL in September 1973 and have worked for that
company ever since (though its name was changed to Fujitsu Services about 10 years ago). During my
time with ICL / Fujitsu I have held a number of roles in customer support, development, design and
architecture. During the early 1990s I was involved with representing ICL in developing Systems
Management Standards and in 1992 I was the head of the UK delegation on Systems Management at the
International Standards Organisation conference in Ottawa, Canada. In the late 1990s I become a
Distinguished Engineer within ICL. Distinguished Engineers, were about 100 or so of the senior technical
staff within the company (out of about 6000 to 7000 technical staff).
I am a member of the British Computer Society (MBCS), a Chartered Engineer (CEng) and a Chartered IT
Professional (CITP).
Since 1996 I have been working on the Horizon project in association with Post Office Ltd. My initial role
was in the integration of the Riposte messaging system which is responsible for storing all data in the Post
Office branches and replicating it to the Data Centres. I was also responsible for the design of the interface
between Horizon and Streamline which processes all Credit and Debit Card payments for Post Office Ltd.
Signature Signature witnessed by
POLOL (Side A)
FUJ00124016
FUJ00124016
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 2 Of 9 Pages
Continuation Statement of Gareth Idris JENKINS
More recently I’ve been involved in projects associated with interfacing data from Horizon to Post Office’s
back end accounting systems.
The purpose of this report is to provide some further background information and relate this to the current
case.
1.1 The Document Structure
Section 2 of the document describes the Horizon system at a high level, giving a time-line for its
development, the Business scope and Architecture diagrams for both the original Horizon System and the
current Horizon Online system.
Section 3 then summarises my views on the overall integrity of the Horizon system.
2. The Horizon System
2.1. Timeline
Fujitsu were originally awarded a contract in 1996 to provide a Horizon System to Post Office Ltd. The
following provides some key dates and functional changes:
Horizon Pilot 1996
Horizon Rollout 1999 — 2002
Network Banking 2003
EMV 2004
Cash Account removed 2005
Data Centre Migration 2009
HNG-X Rollout 2010
Horizon Online (or HNG-X) was a major re-implementation of Horizon. It was a complete re-
implementation of the business functionality at the counter and utilised a central Database to hold details of
all transactions rather than the MessageStore used by the original Horizon system.
All Post Office Branches migrated from the original Horizon to Horizon Online between January and
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POLOM
FUJ00124016
FUJ00124016
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 3 Of 9 Pages
Continuation Statement of Gareth Idris JENKINS
September 2010. Historical transactions were made visible in the new system as part of the migration
process.
2.2 Business Scope
The Business scope of Horizon is:
¢ Point Of Sale Application
Transaction Recording
o Allsuch transactions are Audited
* Posting Summary Transactions to POL SAP (Post Office Ltd’s back end accounting system)
¢ Posting Detailed Transactions to Credence (Post Office Ltd’s back end Management Information
system)
e Posting Remuneration Data to HR-SAP (Royal Mail Group’s back end Payroll system)
© Delivering Client Data to Post Office Ltd’s Clients (ie 3" parties that Post Office Ltd acts as an
agent for such as Local Authorities and Utility companies etc)
2.3. Architecture Diagrams
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POLOM
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 4 Of 9
Continuation Statement of I Gareth Idris JENKINS
: AuditAgent SMT
Oracle Write Write
Audit
Harvester Extract
Agents
Message Audit I Store
store
Audit System
Replication
Audit Retrieval
Journal Message
store
Audit
Counter
Extract
Figure 1 — Horizon Data Flows
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Pages
The Horizon system was designed to store all data locally on the counter’s hard disk in what is referred to
as the messagestore. Once the data has been successfully stored there it is then replicated (copied) to the
hard disks of any other counters in the branch (and in the case of a single counter branch to the additional
external storage on the single counter). Data is also passed on from the gateway counter to the Horizon
data centre using similar mechanisms where it is stored in the CS Messagestore.
The replication process is designed such that should the data fail to be copied immediately (for example
due to a failure on the local IT network within the branch or another counter being switched off or the
branch being disconnected from the data centre), then further attempts are made to replicate the data at
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POLOIL
FUJ00124016
FUJ00124016
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 5 Of 9 Pages
Continuation Statement of Gareth Idris JENKINS
regular intervals until it is finally copied successfully. Once the data reaches the Data Centre a further
copy is taken by the Audit Agent which writes it to an Audit File which is added into the audit trail where it
is available for retrieval for up to 7 years. Data in the audit trail is “sealed” with a secure checksum that is
held separately to ensure that it has not been tampered with or corrupted.
Other systems can also access the data from the CS Messagestore via Harvester Agents. However such
systems are outside the scope of the integrity of the Audit trail.
Every record that is written to the transaction log has a unique incrementing sequence number. This means
it is possible to detect if any transitions records have been lost.
While a customer session is in progress, details of the transactions for that customer session are normally
held in the computer’s memory until the customer session (often known as the “stack”) is settled. At that
point all details of the transactions (including any methods of payment used) are written to the local hard
disk and replicated (as described above). It should be noted that double entry bookkeeping is used when
recording all financial transactions, ie for every sale of goods or services, there is a corresponding entry to
cover the method of payment that has been used. When a “stack” is secured it is written in such a way that
either all the data is written to the local hard disk or none of it is written. This concept of “atomic writes”
is also taken into account when data is replicated to other systems (ie other counters, external storage or the
data centre).
The data for a stack will have been successfully secured to the local hard disk before the screen is updated
indicating that a new customer session can be started. Note that although an attempt will have been made
to replicate the data to an external system at this time, there is no guarantee at this point that such
replication will have been successful. For example if there is a Network Failure followed by a Terminal
failure there is a slight risk that transactions in the intervening period could be lost.
All data that is written includes a “checksum” value (known as a CRC) which is checked whenever the data
is read to ensure that it has not been corrupted. Any such corruptions detected on reading will result in
failures being recorded in the event logs which are held on the local hard disk for a few days for immediate
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POLOM
FUJ00124016
FUJ00124016
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 6 Of 9 Pages
Continuation Statement of I Gareth Idris JENKINS
diagnosis and also immediately sent through to the data centre where they are held for 7 years.
Any failures to write to a hard disk (after appropriate retries) will result in the counter failing and needing
to be restarted and so will be immediately visible to the user.
Whenever data is retrieved for audit enquiries a number of checks are carried out:
1. The audit files have not been tampered with (ie the Seals on the audit files are correct)
2. The individual transactions have their CRCs checked to ensure that they have not been corrupted.
3. A check is made that no records are missing. Each record generated by a counter has an
incremental sequence number and a check is made that there are no gaps in the sequencing.
Other
Systems
Data Copy
Audit Store
BAL Message Audit System
Audit I Retrieval
Counter Augie
Extract
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POLOIL
FUJ00124016
FUJ00124016
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 7 Of 9 Pages
Continuation Statement of Gareth Idris JENKINS
gure 2 — Horizon Online Data Flows
Horizon Online is designed to store all data in an online database known as the Branch Database (BRDB).
In particular no data concerning Business Transactions is retained at the counter other than in the memory
of the Counter Business Application.'
Transactions are carried out locally on the Horizon Online counters and a Basket is built up during a
Customer Session. Each transaction will result in a Basket Entry consisting of one or more Accounting
Lines. At the end of a Customer Session when the Basket has been completed and all Settlement items (or
Tender lines) have been processed and added into the Basket as further Accounting Lines, such that the
total value of the Basket is zero, the entire Basket is sent to the Data Centre as a BAL Message where the
Branch Access Layer (BAL) processes the message and all the Accounting Lines are recorded and
committed to the BRDB as part of a single Oracle Commit. This means that either all the transactions
within a Basket are successfully written or none of them are. Once the Accounting Lines have been
successfully committed a response is returned to the counter indicating this success and this then allows
any receipts to be printed. The Basket is deemed to be fully completed once all relevant receipts have been
successfully printed. Note that if there are no receipts to be printed, then the screen is updated to show the
top level menu indicating successful completion of the previous Basket.
The Oracle Commit also includes an Audit of the data originally transmitted from the counter to the BRDB.
This data is digitally signed at the counter using a key generated as part of the Log On process. It is this
audit record that is used to provide the extract of transactions used for Litigation support.
Any auditable message from the counter is stored, together with its Digital Signature and other key
attributes in an “Audit table” (known as the Message Journal) in BRDB. Each night after midnight, the
contents of this table for the previous day are copied from the BRDB to a number of serial files.
A number of files are generated due to the volume of data processed each day. All data from
1 In order to support recovery, the identifier of the last successfully completed Basket is recorded on the
Hard disk at the counter. However this is not classed as Business Data.
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POLOM
FUJ00124016
FUJ00124016
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 8 Of 9 Pages
Continuation Statement of Gareth Idris JENKINS
a given Branch will be concentrated into a small number of these files for ease of retrieval.
At this point a check is made that indeed there are no missing or duplicate jsns for any counter and should
any be found an alert is raised.
Note that this could only happen as a result of a bug in the code or by somebody tampering
with the data in BRDB and this check is included specifically to check for any such bugs /
tampering.
These files are then copied to the Audit system where they are sealed with digital seals. They are held
there for a period of 7 years during which time they may be retrieved and filtered to produce the relevant
audit data for a particular Branch.
The audit record may also include application events that have been accumulated at the counter since the
last auditable message was sent to the Data Centre. All major activities that affect the Branch also have an
audit of the data sent from the counter to the Data Centre included in the audit log.
Each Audit record includes the following identification:
e Branch identifier (i.e. FAD Code)
* Counter identifier
e Sequence Number (known as a Journal Sequence Number or jsn)
© Counter timestamp
Within any counter (i.e. for a given Branch Id / Counter Id combination), the jsn will always increase by
exactly one for each successive audit record. This enables a check to be made that there are no records
missing from the audit trail when they are retrieved.
The transactions in a basket are constructed using the principle of double-entry bookkeeping. This means
that in addition to the Accounting Lines that relate to the actual business transactions, separate Accounting
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POLOM
FUJ00124016
FUJ00124016
CONFIDENTIAL
Witness Statement
Criminal Justice Act 1967, Section 9, Magistrates Court Act 1980, sub section. SA(3)(a) and SB; Criminal Procedure Rules 2005, Rule 27.1
Page 9 Of 9 Pages
Continuation Statement of Gareth Idris JENKINS
Lines are also generated for the tender items (such as Cash, Cheques or Credit / Debit Cards), resulting in
the total value of all Accounting Lines in a Basket adding up to zero. When the contents of a Basket are
written to BRDB a check is made that the net value of all the accounting lines is indeed zero and should it
not be, then an alert is raised and the basket is discarded and an error response returned to the counter.
Note that this could only happen as a result of a bug in the code and this check is included
specifically to check for any such bugs.
Baskets are also built up during Back Office Sessions and such Back Office baskets are handled in a
similar way to Customer Baskets.
3. Horizon Integrity
This is described in the separate integrity documents ARCGENREP0004.HorizonDatalntegrity.doc which I
now produce as exhibit GIJ/1 and HorizonOnlineDatalntegrity_POL.doc which I now produce as exhibit
GI/2.
I have been involved personally in a number of challenges to the integrity of the original Horizon system
and produced Witness Statements for a number of cases where the Integrity has been challenged. I am not
aware of any cases where the Integrity of Horizon Online has yet been successfully challenged in court.
The main challenges in the cases in which I have been involved were presented as “Hypothetical issues”
and my previous Witness Statements went through each of these hypotheses and showed that there was no
specific evidence for any of them in the data presented.
In summary I would conclude by saying that I fully believe that Horizon will accurately record all data that
is submitted to it and correctly account for it. However it cannot compensate for any data that is
incorrectly input into it as a result of human error, lack of training or fraud (and nor can any other system).
Signature Signature witnessed by
POLOM