ISO/TS 24534-5:2008

TECHNICAL ISO/TS
SPECIFICATION 24534-5
First edition
2008-02-15
Automatic vehicle and equipment
identification — Electronic Registration
Identification (ERI) for vehicles —
Part 5:
Secure communications using
symmetrical techniques
Identification automatique des véhicules et des équipements —
Identification d'enregistrement électronique (ERI) pour les véhicules —
Partie 5: Communications sécurisées utilisant des techniques
symétriques
Reference number
©
ISO 2008
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ii © ISO 2008 – All rights reserved

Contents Page
Foreword. v
Introduction . vi
1 Scope .1
2 Normative references .2
3 Terms and definitions .2
4 Symbols and abbreviations .8
5 System communications concept.9
5.1 General.9
5.2 Overview.9
5.2.1 Vehicle registration identification.9
5.2.2 System concept and supported interfaces .10
5.2.3 Roles involved.11
5.2.4 The communications context for reading .11
5.2.5 The communications context for writing .12
5.2.6 Service levels supported .12
5.3 Security services .13
5.3.1 Assumptions .13
5.3.2 Entity authentication while reading ERI data.13
5.3.3 Confidentiality while reading ERI data .13
5.3.4 Keys for authentication and confidentiality.14
5.3.5 Access control to ERI data .14
5.4 Communication architecture description .14
5.4.1 Overall communication concept for identifying vehicles.14
5.4.2 Overall communication concept for remote access .15
5.4.3 The onboard communication .15
5.5 Interfaces .16
5.5.1 The short-range air interface .16
5.5.2 The onboard interface with the ERT .17
6 Interface requirements .17
6.1 Overview.17
6.2 Abstract transaction definitions.18
6.2.1 Transaction overview .18
6.2.2 Session phases.18
6.2.3 ERI transactions and protocol data units .19
6.2.4 Mutual authentication 1.20
6.2.5 Mutual authentication 2.20
6.2.6 Get secret key ERI data.21
6.2.7 Set secret key ERI data .22
6.2.8 Commissioning secret key ERT.23
6.2.9 Decommissioning secret key ERT.23
6.2.10 Update access control list .24
6.2.11 Get ciphertext access control list entry .25
6.2.12 End of Session.26
6.3 The onboard interface to the ERT.26
6.3.1 General ERT interface requirements .26
6.3.2 An ISO 14443 interface.27
6.4 The short-range air interface .27
6.4.1 General short-range air interface requirements .27
6.4.2 The use of the DRSC application layer protocol .27
6.4.3 Lower layers . 29
6.5 Remote access interface . 29
Annex A (normative) ASN.1 module definitions. 30
Annex B (informative) Operational scenarios. 33
Annex C (normative) PICS pro forma . 36
Bibliography . 38

iv © ISO 2008 – All rights reserved

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
⎯ an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
⎯ an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a
further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an
International Standard or be withdrawn.
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.
ISO/TS 24534-5 was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.
ISO/TS 24534 consists of the following parts, under the general title Automatic vehicle and equipment
identification — Electronic Registration Identification (ERI) for vehicles:
⎯ Part 1: Architecture
⎯ Part 2: Operational requirements
⎯ Part 3: Vehicle data
⎯ Part 4: Secure communications using asymmetrical techniques
⎯ Part 5: Secure communications using symmetrical techniques
Introduction
A quickly emerging need has been identified within administrations to improve the unique identification of
vehicles for a variety of services. Situations are already occurring where manufacturers intend to fit lifetime
tags to vehicles. Various governments are considering the needs/benefits of ERI such as legal proof of vehicle
identity with potential mandatory usages. There is a commercial and economic justification both in respect of
tags and infrastructure that a standard enables an interoperable solution.
Electronic Registration Identification (ERI) is a means of uniquely identifying road vehicles. The application of
ERI will offer significant benefits over existing techniques for vehicle identification. It will be an enabling
technology for the future management and administration of traffic and transport, including applications in free
flow, multi-lane, traffic conditions with the capability to support mobile transactions. ERI addresses the need of
authorities and other users for a trusted electronic identification, including roaming vehicles.
This part of ISO/TS 24534 specifies the interfaces for the exchange of data between an onboard component
containing the ERI data and an ERI reader or writer inside or outside the vehicle using symmetric
cryptographic techniques.
The exchanged identification data consists of a unique vehicle identifier and may also include data typically
found in the vehicle’s registration certificate (see Part 3 for details). The authenticity of the exchanged vehicle
data can be further enhanced by using symmetric encryption techniques, i.e. techniques based on secret keys
shared by a particular community of users.
The ERI interface defined in this part supports confidentiality measures to adhere to (inter)national privacy
regulation and to prevent other misuse of electronic identification of vehicles.
Following the events of September 11 2001, and the subsequent reviews of anti-terrorism measures, the need
for ERI has been identified as a possible anti-terrorism measure. The need for international harmonization of
such ERI is therefore important. It is also important to ensure that any ERI measures contain protection
against misuse by terrorists.
This part of ISO/TS 24534 makes use of the basic automatic vehicle identification (AVI) provisions already
defined in ISO 14814 and ISO 14816. In addition, it includes provisions for security and the use of additional
registration data of a vehicle.

vi © ISO 2008 – All rights reserved

TECHNICAL SPECIFICATION ISO/TS 24534-5:2008(E)

Automatic vehicle and equipment identification — Electronic
Registration Identification (ERI) for vehicles —
Part 5:
Secure communications using symmetrical techniques
1 Scope
This Technical Specification provides the requirements for an Electronic Registration Identification (ERI) using
symmetric encryption techniques that are
⎯ based on an identifier assigned to a vehicle (e.g. for recognition by national authorities),
⎯ suitable to be used for:
⎯ electronic identification of local and foreign vehicles by national authorities;
⎯ vehicle manufacturing, in-life maintenance and end-of-life identification (vehicle life-cycle
management);
⎯ adaptation of vehicle data, e.g. in case of international re-sales;
⎯ safety related purposes;
⎯ crime reduction;
⎯ commercial services, and
⎯ adhering to privacy and data protection regulations.
This part of ISO/TS 24534 specifies the interfaces for a secure exchange of data between an ERT and an ERI
reader or ERI writer in or outside the vehicle using symmetric encryption techniques.
Symmetric encryption techniques are based on secret keys shared by a particular community of users, i.e. in
closed user groups in which it is trusted that keys are not revealed to outsiders.
NOTE The onboard device containing the ERI data is called the electronic registration tag (ERT).
This Technical Specification includes:
⎯ the interface between an ERT and an onboard ERI reader or writer,
⎯ the interface between the onboard ERI equipment and (road side) reading and writing equipment,
⎯ security issues related to the communication with the ERT.
NOTE The vehicle identifiers and possible related vehicle information (as typically contained in a vehicle registration
certificate) are defined in ISO/TS 24534-3, Automatic vehicle and equipment identification — Electronic Registration
Identification (ERI) for vehicles — Part 3: Vehicle data.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO/IEC 8825-2, Information technology — ASN.1 encoding rules: Specification of Packed Encoding Rules
(PER) — Part 2
ISO/IEC 14443 (all parts), Identification cards — Contactless integrated circuit(s) cards — Proximity cards
ISO 14816, Road transport and traffic telematics — Automatic vehicle and equipment identification —
Numbering and data structure
ISO 15628, Road transport and traffic telematics — Dedicated short range communication (DSRC) — DSRC
application layer
EN 12834, Road Transport and Traffic Telematics — Dedicated Short-Range Communication (DSRC) —
DSRC application layer
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
access control
prevention of unauthorized use of a resource, including the prevention of use of a resource in an unauthorized
manner
[ISO 7498-2, definition 3.3.1]
3.2
access control list
list of entities, together with their access rights, which are authorized to have access to a resource
[ISO 7498-2, definition 3.3.2]
3.3
active threat
threat of a deliberate unauthorized change to the state of the system
Note Examples of security-relevant active threats may be: modification of messages, replay of messages, insertion
of spurious messages, masquerading as an authorized entity and denial of service.
[ISO 7498-2, definition 3.3.4]
3.4
additional vehicle data
ERI data in addition to the vehicle identifier
[ISO 24534-3, definition 3.1]
3.5
air Interface
conductor-free medium between OBE and the reader/interrogator through which the linking of the OBE to the
reader/interrogator is achieved by means of electro-magnetic signals
[ISO 14814, definition 3.2]
2 © ISO 2008 – All rights reserved

3.6
authorization
granting of rights, which includes the granting of access based on access rights
[ISO 7498-2, definition 3.3.10]
3.7
challenge
data item chosen at random and sent by the verifier to the claimant, which is used by the claimant, in
conjunction with secret information held by the claimant, to generate a response which is sent to the verifier
[ISO 9798-1, definition 3.3.5]
3.8
ciphertext
data produced, through the use of encipherment; the semantic content of the resulting data is not available
[ISO 7498-2, definition 3.3.14]
3.9
claimant
entity which is or represents a principal for the purposes of authentication, including the functions necessary
for engaging in authentication exchanges on behalf of a principal
[ISO/IEC 10181-2]
3.10
cleartext
intelligible data, the semantic content of which is available
[ISO 7498-2]
3.11
confidentiality
property that information is not made available or disclosed to unauthorized individuals, entities, or processes
[ISO 7498-2]
3.12
data integrity
integrity
property that data has not been altered or destroyed in an unauthorized manner [ISO7498-2]
3.13
decipherment
decryption
reversal of a corresponding reversible encipherment
[ISO 7498-2, definition 3.10]
3.14
distinguishing identifier
information which unambiguously distinguishes an entity
[ISO 9798-1, definition 3.3.9]
3.15
electronic registration identification
ERI
the action or act of identifying a vehicle with electronic means for purposes as mentioned in the scope of this
Technical Specification
3.16
electronic registration reader
ERR
a device used to read or read/write data from or to an ERT
NOTE 1 An ERR communicates directly, i.e. via an OSI data-link, with an ERT.
NOTE 2 An ERR may also be an ERI reader and/or an ERI writer or may act as a relay in the exchange of ERI data
protocol units between an ERT and an ERI reader/writer.
3.17
electronic registration tag
ERT
the onboard ERI device that contains the ERI data, including the relevant implemented security provisions
and one or more interfaces to access that data
NOTE 1 In case of high security, the ERT is a type SAM (secure application module).
NOTE 2 The ERT may be a separate device or may be integrated into an onboard device that also provides other
capabilities (e.g. DSRC communications).
3.18
encipherment
encryption
the cryptographic transformation of data to produce ciphertext
NOTE 1 Encipherment may be irreversible, in which case the corresponding decipherment process cannot feasibly be
performed.
NOTE 2 Adapted from ISO 7498-2, definition 3.3.27.
3.19
end-to-end encipherment
encipherment of data within or at the source end system, with the corresponding decipherment occurring
only within or at the destination end system
[ISO 7498-2, definition 3.3.29]
3.20
entity authentication
corroboration that an entity is the one claimed
[ISO 9798-1, definition 3.3.11]
3.21
ERI data
vehicle identifying data which can be obtained from the ERT that consists of the vehicle identifier and possible
additional vehicle data
[ISO 24534-3, definition 3.4]
3.22
ERI reader
device used to read ERI data directly or indirectly from an ERT by invoking ERI transactions
4 © ISO 2008 – All rights reserved

NOTE 1 In case an ERI reader exchanges the ERI protocol data units directly via a data link with an ERT, it is also
called an ERR. In case it communicates via one or more nodes, only the last node in this sequence is called an ERR. As a
consequence, an external ERI reader may, depending on the onboard configuration, act for some vehicles as an ERR and
for others not.
NOTE 2 See also onboard ERI reader and external ERI reader.
3.23
ERI system operator
organization responsible for the operation of the ERI system and acting as the security authority for the ERI
security domain
3.24
ERI writer
device used to write ERI data directly or indirectly into an ERT by invoking ERI transactions
NOTE 1 In case an ERI writer exchanges the ERI protocol data units directly via a data link with an ERT, it is also
called an ERR. In case it communicates via one or more nodes, only the last node in this sequence is called an ERR. As a
consequence, an external ERI writer may, depending on the onboard configuration, act for some vehicles as an ERR and
for others not.
NOTE 2 See also onboard ERI writer and external ERI writer.
3.25
external ERI reader
ERI reader not being part of the onboard ERI equipment
NOTE 1 An external ERI reader is not fitted within or on the outside of the vehicle.
NOTE 2 A distinction is made between proximity, short-range (DSRC), and remote external readers. A proximity reader
may e.g. be a PCD (Proximity Coupling Device) as specified in ISO 14443. A short-range external ERI reader may be (a
part of) roadside equipment, hand-held equipment, or mobile equipment. A remote external ERI reader may be part of the
back-office equipment (BOE).
3.26
external ERI writer
ERI writer not being part of the onboard ERI equipment
NOTE 1 An external ERI writer is not fitted within or on the outside of the vehicle.
NOTE 2 A distinction is made between proximity, short-range (DSRC), and remote external writers. A proximity reader
may e.g. be a PCD (Proximity Coupling Device) as specified in ISO 14443. A short-range external ERI writer may be (a
part of) roadside equipment, hand-held equipment, or mobile equipment. A remote external ERI writer may be part of the
back-office equipment (BOE).
3.27
identification
action or act of establishing the identity
NOTE See also vehicle identification.
3.28
key
sequence of symbols that controls the operations of a cryptographic transformation (e.g. encipherment,
decipherment, cryptographic check function, signature generation, or signature verification)
[ISO 9798-1, definition 3.3.13]
3.29
lifetime
period of time during which an item of equipment exists and functions
[ISO 14815, definition 4.8]
3.30
manipulation detection
mechanism which is used to detect whether a data unit has been modified (either accidentally or intentionally)
[ISO 7498-2, definition 3.3.35]
3.31
masquerade
pretence by an entity to be a different entity
[ISO 7498-2, definition 3.3.36]
3.32
mutual authentication
entity authentication which provides both entities with assurance of each other’s identity
[ISO 9798-1, definition 3.3.14]
3.33
onboard ERI equipment
equipment fitted within or on the outside of the vehicle and used for ERI purposes
NOTE The onboard ERI equipment comprises an ERT and may also comprise any additional communication devices.
3.34
onboard ERI reader
ERI reader being part of the onboard ERI equipment
NOTE An onboard ERI reader may e.g. be a PCD (proximity coupling device) as specified in ISO 14443.
3.35
onboard ERI writer
ERI writer being part of the onboard ERI equipment
NOTE An onboard ERI writer may e.g. be a PCD (proximity coupling device) as specified in ISO 14443.
3.36
passive threat
threat of unauthorized disclosure of information without changing the state of the system
[ISO 7498-2, definition 3.3.38]
3.37
principal
entity whose identity can be authenticated
[ISO/IEC 10181-2, definition 3.15]
3.38
privacy
right of individuals to control or influence what information related to them may be collected and stored and by
whom and to whom that information may be disclosed
NOTE Because this term relates to the right of individuals, it cannot be very precise and its use should be avoided
except as a motivation for requiring security.
[ISO 7498-2, definition 3.3.43]
3.39
random number
time-variant parameter whose value is unpredictable
[ISO 9798-1, definition 3.3.24]
6 © ISO 2008 – All rights reserved

3.40
registration authority
〈ERI data〉 organization responsible for writing the ERI data and security data into an ERT according to local
legislation
NOTE It is expected that the registration authority with respect to the ERI data may be the same authority that keeps
the official register in which the vehicle and is owner or lessee are listed. This is, however, not required by this Technical
Specification.
3.41
secret key
key that is used with a symmetric cryptographic algorithm
NOTE 1 Possession of a secret key is restricted (usually to two entities).
NOTE 2 For ERI, there may be only one entity or several entities, depending on the key management policy.
NOTE 3 Adapted from ISO/IEC 10181-1, definition 3.3.15.
3.42
security
protection of information and data so that unauthorized persons or systems cannot read or modify them and
authorized persons or systems are not denied access to them
[ISO 12207, definition 3.25]
NOTE Security versus safety (informal):
Security: protection of a system against its environment, in this context the protection of the ERI system against attacks
or accidents;
Safety: protection of the environment against a system, in this context the protection of the driver, passengers, vehicle,
etc., against dangers of the ERI system.
3.43
security authority
entity that is responsible for the definition, implementation or enforcement of security policy
[ISO/IEC 10181-1, definition 3.3.17]
3.44
security domain
set of elements, security policy, security authority and set of security-relevant activities in which the set of
elements are subject to the security policy for the specified activities, and the security policy is administered
by the security authority for the security domain
NOTE Adapted from ISO/IEC 10181-1, definition 3.3.20.
3.45
security service
service, provided by a layer of communicating open systems, which ensures adequate security of the systems
or of data transfers
[ISO 7498-2, definition 3.3.51]
3.46
sequence number
time variant parameter whose value is taken from a specified sequence which is non-repeating within a certain
time period
[ISO 9798-1, definition 3.3.27]
3.47
system operator
organization responsible for the operation of the system
NOTE For this part of ISO/TS 24534, a system operator also acts as the registration authority and the security
authority in his jurisdiction.
3.48
system operator key
access key for a system operator
3.49
threat
potential violation of security
[ISO 7498-2, definition 3.3.55]
3.50
vehicle identification
action or act of establishing the identity of a vehicle
3.51
verifier
entity which is or represents the entity requiring an authenticated identity
NOTE 1 A verifier includes the functions necessary for engaging in authentication exchanges.
NOTE 2 Adapted from ISO/IEC 10181-2, definition 3.20.
4 Symbols and abbreviations
AEI Automatic Equipment Identification
AES Advanced Encryption Standard
ASN.1 Abstract Syntax Notation One (as defined in ISO 8824)
AVI Automatic Vehicle Identification
BOE Back Office Equipment
DES Data Encryption Standard
EN Europäische Norm (German), English: European Standard
ENV Europäische Norm Vorausgabe (German), English: European Pre-Standard
ERI Electronic Registration Identification
ERR Electronic Registration Reader: a device used to read or read/write data from or to an ERT
ERT Electronic Registration Tag
EU European Union
IEC International Electrotechnical Commission
8 © ISO 2008 – All rights reserved

ISO International Organization for Standardization
OBE OnBoard Equipment
OSI Open Systems Interconnection (see ISO/IEC 7498-1)
PICS Protocol Implementation Conformance Statement(s)
PIN Personal Identification Number
SAM Secure Application Module
Triple- Triple-Data Encryption Standard
DES
VIN Vehicle Identification Number
5 System communications concept
5.1 General
Clause 5 is informative only.
This clause provides an introduction of the context in which ERI data and security data may be read from or
written into the ERT and in which vehicles can be identified. It also outlines options that may or may not be
used in an actual implementation. The normative requirements for the interfaces are provided in Clause 6 and
Annex A. Annex C contains a form to specify the limitations of an actual communication protocol
implementation.
This clause only deals with interfaces using symmetric encryption techniques. Symmetric encryption
techniques are based on secret keys that are shared by a community of one or more users. Such a
community is essentially a closed user group in which it is trusted that secret keys are not revealed to
outsiders.
It is assumed that the users of the closed user group are all operating within the jurisdiction of one ERI system
operator responsible for key management and acting as the registration authority in his jurisdiction.
A more generic interface based on asymmetric techniques, with various (security) capability levels and
supporting cooperation between multiple (registration) authorities (i.e. multiple security domains) is defined in
ISO/TS 24534-4.
5.2 Overview
5.2.1 Vehicle registration identification
ERI, Electronic Registration Identification, is the action or act of identifying a vehicle with electronic means for
purposes as mentioned in the scope of this part Technical Specification.
The identifier used to identify a vehicle is called the vehicle identifier or vehicleId.
NOTE The preferred vehicle identifier is the VIN that is assigned to the vehicle by its manufacturer in accordance to
ISO 3779 but alternatives are supported as well. See ISO/TS 24534-3, Automatic vehicle and equipment identification —
Electronic Registration Identification (ERI) for vehicles — Part 3: Vehicle data, for details about the vehicle identifier and
additional vehicle data.
In this Technical Specification, the combination of the almost unique vehicleId and a unique ERT number is
used as the unambiguous distinguishing identifier.
5.2.2 System concept and supported interfaces
Figure 1 presents the interfaces specified in this part of Technical Specification.

Figure 1 — System concept and supported interfaces
The onboard component that provides a secure environment for the ERI data and security data is called the
electronic registration tag (ERT).
NOTE An implementer may integrate other provisions into the ERT, as long as this does not compromise the security
of the ERT.
An ERT operates in one of two modes:
⎯ Non-commissioned mode,
when the ERT contains no system operator keys.
When operating in the non-commissioned mode, the authentication phase (see below) is not supported
and the only operation allowed is to commission the ERT.
⎯ Commissioned mode,
when a system operator has written its keys into the ERT.
When operating in the commissioned mode the authentication phase (see below) is supported.
A system operator may also decommission an ERT, i.e. delete all key from the ERT. The ERT then returns to
its non-commissioned mode and the only operation allowed is again to commission the ERT.
An ERT is tailored to a specific vehicle in one or more steps:
⎯ First, the ERT is customized with the vehicle identifier and, optionally, additional ERI data.
This step can only be performed once in the lifetime of an ERT.
⎯ Next, the system operator may register changes of the additional ERI data (i.e. the ERI data with the
exception of the vehicle identifier).
ERI data may only be written/updated in commissioned mode and only by the system operator.
10 © ISO 2008 – All rights reserved

It is assumed that all ERT and all onboard and external readers and writers will be part of the same security
domain, i.e. within the jurisdiction of one single ERI system operator responsible for the security policy and its
implementation.
It is also assumed that the system operator is also acting as the registration authority in their jurisdiction.
NOTE 1 In order to accommodate the needs of different system operators, different selections of additional ERI data
can be included in an ERT (see ISO 24534-3 for details).
The onboard communication provisions shall be capable to transfer data from or to the ERT without modifying
that data.
NOTE 2 The onboard communication provisions may e.g. be part of an onboard platform for transport applications.
A communication device may communicate with a short-range ERI reader/writer or remote with back office
equipment (BOE).
A onboard communication device external to the ERT that communicates with an external ERI reader/writer
acts as a relay between this external ERI reader/writer and the onboard ERI reader/writer. A communication
device may also be used for other applications.
5.2.3 Roles involved
Within the context of this Technical Specification, the following “roles” for natural or legal persons are
distinguished.
a) A system operator, who is responsible for the operation of the ERI system. An ERI system operator is
also the security authority for the ERI security domain and responsible for generating secret keys to be
used for authentication. A system operator also acts as the registration authority, i.e. as the authority for
writing vehicle-related data into the ERT.
NOTE 1 It is expected that the registration authority with respect to the ERI data is the same authority that keeps
the register in which the vehicle is listed. This is, however, not required by this Technical Specification.
NOTE 2. It is assumed that each vehicle is listed in a register that contains the vehicle identifier and additional data
related to the vehicle. It is implicitly assumed that this register also identifies the one(s) responsible for the vehicle
(e.g. its owner, operator, keeper, lessee, and/or regular driver).
b) Authorities, who are entitled (e.g. by the virtue of public legislation) and authorized by the system operator
to read the ERI data and encrypted access control list entries from a vehicle.
NOTE 3 Roles and requirements related to the specification, design and manufacturing (including testing) of an
ERT are outside the scope of this part of this Technical Specification.
5.2.4 The communications context for reading
Figure 2 presents the communications context for reading data from an ERT.
An onboard or external ERI reader is used to read data from the ERT. An onboard ERI reader communicates
directly with the ERT. An external ERI reader communicates either directly or indirectly with the ERT: directly
in case of a hand-held reader or an integrated ERI device, or indirectly via an onboard communication module
and an onboard ERI reader. The onboard communication module may also be used for other applications.
A sensor system (outside the scope of this Technical Specification) may be used to trigger an external ERI
reader when it senses the presence of a vehicle.
The various parties that can read ERI data from an ERT are described in 5.2.3. The access rights of the
various entities are described in 5.3.5.
Figure 2 — Communication context for reading from an ERT
The equipment used by an entity in an office (i.e. not at the roadside) is called back office equipment (BOE).
The distribution of functions between BOE and an external ERI reader is outside the scope of this Technical
Specification.
5.2.5 The communications context for writing
Figure 3 presents the communications context for writing data into an ERT.
The onboard or external ERI writer is used to write data into the ERT. An onboard ERI writer communicates
directly with the ERT. An external ERI writer communicates either directly or indirectly with the ERT: directly in
case of a hand-held reader or an integrated ERI device, or indirectly via an onboard communication module
and the onboard ERI writer. The onboard communication module may also be used for other applications.
The various parties that can write ERI (security) data into an ERT are described in 5.2.3. The access rights of
the various entities are described in 5.3.5.
The distribution of functions between BOE and an external ERI writer is outside the scope of this Technical
Specification. A system operator may e.g. commission a writer to operate on its behalf or it may use e.g. the
writer only as a relay device for remote writing from its back office.

Figure 3 — Communication context for writing into an ERT
5.2.6 Service levels supported
This part of ISO/TS 24534 supports a secure communication with an ERT within one jurisdiction based on
symmetric encryption techniques.
A more generic interface based on asymmetric techniques, with various (security) capability levels and
supporting cooperation between multiple (registration) authorities (i.e. security domains) is defined in
ISO/TS 24534-4.
12 © ISO 2008 – All rights reserved

5.3 Security services
5.3.1 Assumptions
The security concept for the exchange of data between an ERT and an ERI reader or writer is based on the
following assumptions.
a) The use of an ERT may be mandatory and, therefore, should be fraud resistant. Using ISO 7498-2
terminology, the ERT should be resistant against active threats (e.g. modification of messages, replay of
messages, insertion of spurious messages, and masquerading).
b) A reading of an ERT should be suitable as legal evidence.
c) ERI shall have the capability to provide a high level of privacy protection (i.e. it should not be easily
possible to monitor mobility patterns of a vehicle and, hence, of its regular driver); consequently, an ERT
should also be resistant against passive threats.
d) ERI shall have the capability to provide protection measures to prevent ERI from being used to trigger an
attack on a vehicle.
e) The performance of security mechanisms must be achievable within the time available for
communications whilst the vehicle is moving.
EXAMPLE Reading a vehicle at 180 km/h within a 10 m read range should be achieved within 200 ms.
5.3.2 Entity authentication while reading ERI data
Trust in the authenticity of an ERI reading depends the following authentication aspects which must all be
fulfilled to fully trust a reading.
a) The ERT is customized with the correct vehicle identifier and is attached to the correct vehicle.
b) The ERT cannot be removed from the vehicle without rendering it inoperable.
c) The ERI data is read from a genuine ERT, i.e. from a legitimate device (it is not a replicated message
from a fake one).
d) The ERI data is correctly read from the ERT (data integrity, manipulation detection). This is achieved by
standard mechanisms used in data communications and, as a side effect, by encrypting the ERI data
(decipherment of corrupted ciphertext will not produce anything useful).
e) When ERI data has been correctly read from a genuine ERT upon a particular request, it shall be difficult
to be disputed later on that this data was not read from this component upon that request. This is
achieved by encrypting the ERI data together with a challenge code provided by the ERI reader.
NOTE 1 This part of ISO/TS 24534 only deals with c), d), and e). The items a) and b) are specified in ISO/TS 24534-2,
Automatic vehicle and equipment identification — Electronic Registration Identification (ERI) for vehicles — Part 2:
Operational requirements.
NOTE 2 Using technical (ISO/IEC 9798-2) terminology, c) and e) are supported using a three pass mutual
authentication mechanism with unidirectional keys. Uniqueness/timeliness is controlled by generating and checking
random numbers and sequence numbers.
5.3.3 Confidentiality while reading ERI data
This Technical Specification supports confidentiality by delivering ERI data in ciphertext. The encrypted ERI
data can then be made freely available but can only be decrypted and interpreted by authorized
persons/equipment (end-to-end encipherment).
...