ISO 13491-2:2016

INTERNATIONAL ISO
STANDARD 13491-2
Third edition
2016-03-15
Financial services — Secure
cryptographic devices (retail) —
Part 2:
Security compliance checklists for
devices used in financial transactions
Services financiers — Dispositifs cryptographiques de sécurité
(services aux particuliers) —
Partie 2: Listes de contrôle de conformité de sécurité pour les
dispositifs utilisés dans les transactions financières
Reference number
ISO 13491-2:2016(E)
©
ISO 2016

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ISO 13491-2:2016(E)

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ISO 13491-2:2016(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Use of security compliance checklists . 2
4.1 General . 2
4.2 Informal evaluation . 3
4.3 Semi-formal evaluation . 3
4.4 Strict semi-formal evaluation . 3
4.5 Formal evaluation . 3
Annex A (normative) Physical, logical, and device management characteristics common to
all secure cryptographic devices . 4
Annex B (normative) Devices with PIN entry functionality .12
Annex C (normative) Devices with PIN management functionality .17
Annex D (normative) Devices with message authentication functionality .20
Annex E (normative) Devices with key generation functionality .22
Annex F (normative) Devices with key transfer and loading functionality .27
Annex G (normative) Devices with digital signature functionality .33
Annex H (normative) Categorization of environments .35
Bibliography .39
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ISO 13491-2:2016(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 68, Financial services, Subcommittee SC 2,
Security.
This third edition cancels and replaces the second edition (ISO 13491-2:2005), which has been
technically revised.
ISO 13491 consists of the following parts, under the general title Financial Services — Secure
cryptographic devices (retail):
— Part 1: Concepts, requirements and evaluation methods,
— Part 2: Security compliance checklists for devices user in financial transactions
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ISO 13491-2:2016(E)

Introduction
This part of ISO 13491 specifies both the physical and logical characteristics and the management of the
secure cryptographic devices (SCDs) used to protect messages, cryptographic keys, and other sensitive
information used in a retail financial services environment.
The security of retail financial services is largely dependent upon the security of these cryptographic
devices.
Security requirements are based upon the premise that computer files can be accessed and manipulated,
communication lines can be “tapped”, and authorized data or control inputs in a system device can be
replaced with unauthorized inputs. While certain cryptographic devices (e.g. host security modules)
reside in relatively high-security processing centres, a large proportion of cryptographic devices used in
retail financial services (e.g. PIN entry devices, etc.) now reside in non-secure environments. Therefore,
when PINs, MACs, cryptographic keys, and other sensitive data are processed in these devices, there is a
risk that the devices may be tampered with, or otherwise, compromised to disclose or modify such data.
It is to be ensured that the risk of financial loss is reduced through the appropriate use of cryptographic
devices that have proper physical and logical security characteristics and are properly managed. To
ensure that SCDs have the proper physical and logical security, they require evaluation.
This part of ISO 13491 provides the security compliance checklists for evaluating SCDs used in financial
services systems in accordance with ISO 13491-1. Other evaluation frameworks exist and may be
appropriate for formal security evaluations, e.g. ISO/IEC 15408-1, ISO/IEC 15408-2, ISO/IEC 15408-3,
and ISO/IEC 19790, and are outside the scope of this part of ISO 13491.
Appropriate device characteristics are necessary to ensure that the device has the proper operational
capabilities and provides adequate protection for the data it contains. Appropriate device management
is necessary to ensure that the device is legitimate, that it has not been modified in an unauthorized
manner, e.g. by “bugging”, and that any sensitive data placed within the device (e.g. cryptographic keys)
have not been subject to disclosure or change.
Absolute security is not practically achievable. Cryptographic security depends upon each life cycle
phase of the SCD and the complementary combination of appropriate device management procedures
and secure cryptographic characteristics. These management procedures implement preventive
measures to reduce the opportunity for a breach of cryptographic device security. These measures aim
for a high probability of detection of any illicit access to sensitive or confidential data in the event that
device characteristics fail to prevent or detect the security compromise.
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INTERNATIONAL STANDARD ISO 13491-2:2016(E)
Financial services — Secure cryptographic devices
(retail) —
Part 2:
Security compliance checklists for devices used in financial
transactions
1 Scope
This part of ISO 13491 specifies checklists to be used to evaluate secure cryptographic devices (SCDs)
incorporating cryptographic processes as specified in H.5, ISO 9564-2, ISO 16609, ISO 11568-1,
ISO 11568-2, and ISO 11568-4 in the financial services environment. IC payment cards are subject to
the requirements identified in this part of ISO 13491 up until the time of issue after which they are to
be regarded as a “personal” device and outside of the scope of this part of ISO 13491.
This part of ISO 13491 does not address issues arising from the denial of service of an SCD.
In the checklists given in Annexes A to H, the term “not feasible” is intended to convey the notion that
although a particular attack might be technically possible, it would not be economically viable since
carrying out the attack would cost more than any benefits obtained from a successful attack. In addition
to attacks for purely economic gain, malicious attacks directed toward loss of reputation need to be
considered.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 11568-1, Banking — Key management (retail) — Part 1: Principles
ISO 11568-2, Financial services — Key management (retail) — Part 2: Symmetric ciphers, their key
management and life cycle
ISO 11568-4, Banking — Key management (retail) — Part 4: Asymmetric cryptosystems — Key
management and life cycle
ISO 13491-1, Financial services — Secure cryptographic devices (retail) — Part 1: Concepts, requirements
and evaluation methods
ISO 16609, Financial services — Requirements for message authentication using symmetric techniques
ISO/IEC 18031, Information technology — Security techniques — Random bit generation
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13491-1 and the following apply.
3.1
auditor
one who has the appropriate skills to check, assess, review, and evaluate compliance with an informal
evaluation on behalf of the sponsor or audit review body
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3.2
data integrity
property that data has not been altered or destroyed in an unauthorized manner
3.3
dual control
process of utilizing two or more entities (usually persons) operating in concert to protect sensitive
functions or information whereby no single entity is able to access or use the materials
Note 1 to entry: A cryptographic key is an example of the type of material to be accessed or utilized.
3.4
evaluation agency
organization trusted by the design, manufacturing, and sponsoring entities which evaluates the SCD
(using specialist skills and tools) in accordance with ISO 13491
3.5
exclusive or
bit-by-bit modulo two addition of binary vectors of equal length
3.6
security compliance checklist
list of auditable claims, organized by device type, as specified in this part of ISO 13491
3.7
sensitive state
device condition that provides access to the secure operator interface such that it can only be entered
when the device is under dual or multiple control
4 Use of security compliance checklists
4.1 General
These checklists shall be used to assess the acceptability of cryptographic equipment upon which
the security of the system depends. It is the responsibility of any sponsor, approval authority, or
accreditation authority, depending on the evaluation method chosen, that adopts some or all of these
checklists to
a) approve evaluating agencies for use by suppliers to or participants in the system, and
b) set up an audit review body to review the completed audit checklists.
Annexes A to H provide checklists defining the minimum evaluation to be performed to assess the
acceptability of cryptographic equipment. Additional tests may be performed to reflect the state-of-
the-art at the time of the evaluation.
The evaluation may be either “informal”, “semi-formal”, or “strict semi-formal” as specified in
ISO 13491-1. Should a “formal” evaluation be chosen, these audit checklists shall not be used as
presented here, but shall rather be used as input to assist in the preparation of the “formal claims” that
such an evaluation requires.
NOTE These formal claims, as they inherently include other criteria, are themselves outside of the scope of
this part of ISO 13491.
A cryptographic device achieves security both through its inherent characteristics and the
characteristics of the environment in which the device is located. When completing these audit
checklists, the environment in which the device is located shall be considered, e.g. a device intended for
use in a public location could require greater inherent security than the equivalent device operating in
a controlled environment. So that an evaluating agency need not investigate the specific environment
where an evaluated device may reside, this part of ISO 13491 provides a suggested categorization
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ISO 13491-2:2016(E)

of environments in Annex H. Thus, an evaluating agency may be asked to evaluate a given device
for operation in a specific environment. Such a device can be deployed in a given facility, only if this
facility itself has been audited to ensure that it provides the ensured environment. However, these audit
checklists may be used with categorizations of the environment other than those suggested in Annex H.
The four evaluation methods specified in ISO 13491-1 are described in 4.2, 4.3, 4.4, and 4.5.
4.2 Informal evaluation
As part of an informal evaluation, an independent auditor shall complete the appropriate checklist(s)
for the device being evaluated.
4.3 Semi-formal evaluation
In the semi-formal method, the sponsor, who may be the manufacturer, shall submit a device to an
evaluation agency for testing against the appropriate checklist(s).
4.4 Strict semi-formal evaluation
In the strict semi-formal method, the sponsor, who may be the manufacturer, shall submit a device to an
evaluation agency for testing against the appropriate checklist(s) determined by an approval authority.
4.5 Formal evaluation
In the formal method, the manufacturer or sponsor shall submit a device to an accredited evaluation
agency for testing against the formal claims where the appropriate checklist(s) were used as input.
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ISO 13491-2:2016(E)

Annex A
(normative)

Physical, logical, and device management characteristics common
to all secure cryptographic devices
A.1 General
This Annex is intended for use with all evaluations and shall be completed prior to any device-specific
security compliance checklists.
The following statements in this security compliance checklist are required to be specified by the
auditor as “true (T)”, “false (F)”, or “not applicable (N/A)”. A “false” indication does not necessarily
indicate unacceptable practice, but shall be explained in writing. Those statements that are indicated as
“N/A” shall also be explained in writing.
A.2 Device characteristics
A.2.1 Physical security characteristics
A.2.1.1 General
All devices shall meet the criteria given in A.2.1.2 for general security characteristics and the criteria
given in A.2.1.5 for tamper responsive characteristics and in A.2.1.3 for tamper-evident characteristics.
Other devices shall additionally meet the criteria given in A.2.1.4 for tamper-resistant characteristics.
A.2.1.2 General security characteristics
An evaluation agency has evaluated the device bearing in mind susceptibility to physical and logical
attack techniques known at the time of the evaluation such as (but not limited to) the following:
— chemical attacks (solvents);
— scanning attacks (scanning electron microscope);
— mechanical attacks (drilling, cutting, probing, etc.);
— thermal attacks (high and low temperature extremes);
— radiation attacks (X-rays);
— information leakage through covert (side) channels (power supply, timing, etc.);
— failure attacks;
and has concluded the following:
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ISO 13491-2:2016(E)

Table A.1 — General security characteristics
No. Security compliance statement True False N/A
A1 It is not feasible to determine a PIN, a key, or other secret
information by monitoring (e.g. the electro-magnetic
emissions from the device with or without the cooperation
of the device operator).
A2 Any ventilation and other openings in the module are
positioned and protected so that it is not feasible to use
such an opening to probe any component of the module
such that plaintext PINs, access codes, or cryptographic
keys might be disclosed or to disable any of the protection
mechanisms of the device.
A3 All sensitive data and cryptographic keys, including
residues, are stored in the security module.
A4 All transfer mechanisms within the device are implemented
in such a way that it is not feasible to monitor the device to
obtain unauthorized disclosure of any such information.
A5 Any access entry point into the device’s internal circuitry is
locked in the closed position when the device is operative,
by means of one or more pick-resistant locks or similar
security mechanisms.
A6 The design of the device is such that a duplicate device
cannot be constructed from components which are available
through retail commercial channels.
A7 If the device generates random numbers or pseudo random
numbers, then the generation of those numbers complies
with ISO 18031.
A8 If the device generates random numbers or pseudo random
numbers, it is not feasible to influence the output of those
numbers, e.g. by varying environmental conditions of the
device such as resetting or reinitializing the device, or
manipulating the power supply/electro-magnetic injection.
A.2.1.3 Tamper-evident characteristics
The evaluating agency has concluded the following:
Table A.2 — Tamper-evident characteristics
No. Security compliance statement True False N/A
A9 The device is designed and constructed so that it is not
feasible to penetrate the device in order to
—   make any additions, substitutions, or modifications
(e.g. the installation of a bug) to the hardware or software
of the device, or
—   determine or modify any sensitive information
(e.g. PINs, access codes, and cryptographic keys)
and then subsequently, return the device without requiring
specialized skills and equipment not generally available and
a)   without damaging the device so severely that the
damage would have a high probability of detection, or
b)   requiring that the device be absent from its intended
location for a sufficiently long time that its absence or reap-
pearance would have a high probability of being detected.
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ISO 13491-2:2016(E)

A.2.1.4 Tamper-resistant characteristics
The evaluating agency has concluded the following:
Table A.3 — Tamper-resistant characteristics
No. Security compliance statement True False N/A
A10 The device is protected against penetration by employing
physical protection to such a degree that penetration is not
feasible.
A11 Even after having gained unlimited, undisturbed access to
the device, discovery of secret information in the target
device is not feasible.
A.2.1.5 Tamper-responsive characteristics
The evaluating agency has concluded the following:
Table A.4 — Tamper-responsive characteristics
No. Security compliance statement True False N/A
A12 The device is protected against penetration by including
features that detect any feasible attempts to tamper with
the device and cause immediate erasure of all cryptographic
keys and sensitive data when such an attempt is detected.
A13 Removal of the case or the opening, whether authorized or
unauthorized of any access entry to the device’s internal
components, causes the automatic and immediate erasure
of the cryptographic keys stored within the device.
A14 There is a defined method for ensuring that secret data or
any cryptographic key that has been used to encrypt secret
data is erased from the unit when permanently removing the
unit from service (decommissioning). There is also a defined
method for ensuring, when permanently decommissioned,
that any cryptographic key contained in the unit that might be
usable in the future is either erased from the unit or is
invalidated at all facilities with which the unit is capable of
performing cryptographically protected communications.
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Table A.4 (continued)
No. Security compliance statement True False N/A
A15 Any tamper detection/key erasure mechanisms function
even in the absence of applied power.
A16 If the device has no mechanism for detection of removal from
its operational environment, then defeating the tamper
detection mechanisms or discovery of secret information
in the target device is not feasible, even when removed from
its operational environment. Compromise of the device
requires equipment and skill sets that are not readily available.
As a possible example, discovery of such information
requires a significant time, such as one month of preparation,
including analysis of other devices and at least one week of
effort to compromise the device after having gained unlimited,
undisturbed access to the target device.
A17 If the device has a mechanism for detection of removal from
its operational environment, then defeating the tamper-
detection mechanisms or discovery of secret information in
the target device is not feasible. Compromise of the device
shall require skill sets that are not readily available and
equipment that is not readily available at the device site nor
can be feasibly transported to the device site.
As a possible example, discovery of such information
requires a significant time, such as one month of preparation,
including analysis of other devices and at least 12 h of
unlimited, undisturbed access to the target device.
A.2.2 Logical security characteristics
The evaluating agency has concluded the following:
Table A.5 — Logical security characteristics
No. Security compliance statement True False N/A
A18 The device includes self-test capabilities capable of manual
or automatic initiation to ensure that its basic functions are
operating properly.
A19 The device only performs its designed functions.
A20 It is not feasible to determine a key or other secret
information by the use of diagnostic or special test modes.
A21 The cryptographic algorithms, modes of operation, and
lengths of cryptographic keys used by the device comply
with ISO 11568-1, ISO 11568-2, and ISO 11568-4.
A22 The device key management complies with ISO 11568-1,
ISO 11568-2, and ISO 11568-4 using each key for only one
cryptographic purpose (although a variant of a key may
be used for a different purpose).
A23 The functionality implemented within the device is such that
there is no feasible way in which plaintext secret information,
(e.g. PINs or cryptographic keys) or secret information
enciphered under other than the legitimate key, can be
obtained from the device, except in an authorized manner
(e.g. PIN mailers).
A24 If the device is composed of several components, it is not
possible to move a secret cryptographic key within the
device from a component of higher security to a component
providing lower security.
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Table A.5 (continued)
No. Security compliance statement True False N/A
A25 The loading of keys is performed when
—   the device is in a sensitive state, or
—   the action of loading a key puts the device into a mode
that activates all the tamper protection mechanisms within
the device.
A26 The following operator functions that may influence the
security of a device are only permitted when the device is
in a sensitive state, i.e. under dual or multiple control:
—   disabling or enabling of device functions;
—   change of passwords or data that enable the device to
enter the sensitive state.
A27 The secure operator interface is so designed that entry of
more than one password (or some equivalent mechanism for
dual or multiple control) is required in order to enter this
sensitive state.
A28 The secure operator interface is so designed that it is highly
unlikely that the device can inadvertently be left in the
sensitive state.
A29 If sensitive state is established with multiple limits (e.g. on the
number of function calls and a time limit), the device returns
to normal state when the first of these limits is reached.
A30 Where passwords or other plaintext data are used to control
transition to a sensitive state, then these are protected in the
same manner as other secret or sensitive information.
A31 If cryptographic keys are lost for any reason, e.g. long-term
absence of applied power, the device will enter a non-
operational state.
A32 The only function calls and sensitive operator functions that
exist in the device are functions approved by the sponsor or
the system in which the device is to operate.
A33 Keys are never translated from encipherment under one
variant to encipherment under another variant of the same key.
A.3 Device management
A.3.1 General consideration
For each life cycle stage, the entity responsible for completing the audit checklist for that stage has
provided assurance for the following:
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Table A.6 — General consideration
No. Security compliance statement True False N/A
A34 For audit and control purposes, the identity of the device
(e.g. its serial number) can be determined, either by external
tamper-evident marking or labelling, or by a command that
causes the device to return its identity via the interface or via
the display.
A35 When the device is in a life cycle stage such that it contains
cryptographic keys, the identity of these keys can be easily
determined from the identity of the device [so that the key(s)
can be invalidated if the device is reported lost or stolen].
A36 Any physical keys used to unlock or operate the device are
carefully controlled and available only to authorized persons.
A37 If a device contains a secret cryptographic key and there is an
attack on a device, or a device is stolen, then procedures are
in place to notify the party responsible for the security o
...