ETSI TS 133 503 V17.2.0 (2023-01)

5G; Security Aspects of Proximity based Services (ProSe) in the 5G System (5GS) (3GPP TS 33.503 version 17.2.0 Release 17)

RTS/TSGS-0333503vh20

General Information

• Status: Not Published
• Technical Committee: 3GPP SA 3 - Security
• Current Stage: 12 - Citation in the OJ (auto-insert)
• Completion Date: 13-Jan-2023

Standards Content (Sample)

TECHNICAL SPECIFICATION
5G;
Security Aspects of Proximity based Services (ProSe)
in the 5G System (5GS)
(3GPP TS 33.503 version 17.2.0 Release 17)

3GPP TS 33.503 version 17.2.0 Release 17 1 ETSI TS 133 503 V17.2.0 (2023-01)

Reference
RTS/TSGS-0333503vh20
Keywords
5G
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ETSI
3GPP TS 33.503 version 17.2.0 Release 17 2 ETSI TS 133 503 V17.2.0 (2023-01)
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Modal verbs terminology
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3GPP TS 33.503 version 17.2.0 Release 17 3 ETSI TS 133 503 V17.2.0 (2023-01)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 6
1 Scope . 8
2 References . 8
3 Definitions of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 9
3.3 Abbreviations . 9
4 Overview . 10
4.1 General . 10
4.2 Reference points and functional entities . 10
4.2.1 Functional entities . 10
4.2.1.1 General . 10
4.2.1.2 5G ProSe Key Management Function . 10
4.2.1.3 Prose Anchor Function . 11
4.2.2 Reference points . 11
5 Common security procedures . 11
5.1 General . 11
5.2 Network domain security . 11
5.2.1 General . 11
5.2.2 Security of Npc2 reference point . 11
5.2.2.1 General . 11
5.2.2.2 Security requirements. 12
5.2.2.3 Security procedures . 12
5.2.3 Security of UE - 5G DDNMF interface . 12
5.2.3.1 General . 12
5.2.3.2 Security requirements. 12
5.2.3.3 Security procedures for configuration transfer to UICC . 12
5.2.3.4 Security procedures for PC3a using GBA . 12
5.2.3.5 Security procedures for PC3a using AKMA . 12
5.2.3.6 Privacy issue in PC3a interface . 13
5.2.4 Security of service-based interfaces used in 5G Prose . 13
5.2.4.1 Security requirements. 13
5.2.4.2 Security procedures . 13
5.2.5 Security for UE - 5G PKMF interface . 13
5.2.5.1 General . 13
5.2.5.2 Security requirements. 13
5.2.5.3 Security procedures for PC8 using GBA . 13
5.2.5.4 Security procedures for PC8 using AKMA . 14
6 Security for 5G ProSe features . 14
6.1 Security for 5G ProSe Discovery . 14
6.1.1 General . 14
6.1.2 Security requirements . 14
6.1.3 Security procedures. 14
6.1.3.1 Open 5G ProSe Direct Discovery . 14
6.1.3.2 Restricted 5G ProSe Direct Discovery . 17
6.1.3.2.1 General . 17
6.1.3.2.2 Security flows . 17
6.1.3.2.3 Protection of discovery messages over PC5 interface . 25
6.2 Security for unicast mode 5G ProSe Direct Communication . 26
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6.2.1 General . 26
6.2.2 Security requirements . 26
6.2.3 Security procedures. 26
6.2.4 Identity privacy for the PC5 unicast link . 26
6.3 Security for 5G ProSe UE-to-Network Relay Communication . 27
6.3.1 General . 27
6.3.2 Security requirements . 27
6.3.3 Security for 5G ProSe Communication via 5G ProSe Layer-3 UE-to-Network Relay . 27
6.3.3.1 Security requirements. 27
6.3.3.2 Security procedure over User Plane . 28
6.3.3.2.1 General . 28
6.3.3.2.2 PC5 security establishment for 5G ProSe UE-to-Network relay communication over User
Plane . 29
6.3.3.2.3 PC5 Key Hierarchy over User Plane . 33
6.3.3.3 Security procedure over Control Plane . 33
6.3.3.3.1 General . 33
6.3.3.3.2 PC5 security establishment for 5G ProSe UE-to-Network relay communication over Control
Plane . 34
6.3.3.3.3 PC5 Key Hierarchy over Control Plane . 38
6.3.3.3.4 Void . 38
6.3.3.4 Security for 5G ProSe Communication via Layer-3 UE-to-Network Relay with N3IWF support . 38
6.3.4 Security for 5G ProSe Communication via 5G ProSe Layer-2 UE-to-Network Relay . 39
6.3.5 Direct Communication Request in 5G ProSe UE-to-Network Relay Communication . 39
6.3.5.1 General . 39
6.3.5.2 Privacy protection of UP-PRUK ID and RSC in DCR . 39
6.3.5.3 Integrity protection of DCR . 40
6.4 Security for broadcast mode 5G ProSe Direct Communication . 40
6.4.1 General . 40
6.4.2 Security requirements . 40
6.4.3 Security procedures. 40
6.5 Security for groupcast mode 5G ProSe Direct Communication . 41
6.5.1 General . 41
6.5.2 Security requirements . 41
6.5.3 Security procedures. 41
7 5G ProSe services . 41
7.1 General . 41
7.2 5G PKMF Services . 41
7.2.1 General . 41
7.2.2 Npkmf_PKMFKeyRequest service . 41
7.2.2.1 Npkmf_PKMFKeyRequest_ProseKey service operation . 41
7.3 AUSF services . 42
7.3.1 General . 42
7.3.2 Nausf_UEAuthentication service . 42
7.3.2.1 Nausf_UEAuthentication_ProseAuthenticate service operation . 42
7.3.2.2 Void. 43
7.4 UDM Services . 43
7.4.1 General . 43
7.4.2 Nudm_UEAuthentication Service . 43
7.4.2.1 Nudm_UEAuthentication_GetProseAv service operation . 43
7.4.3 Nudm_UEIdentifier Service . 43
7.4.3.1 Nudm_UEIdentifier_Deconceal service operation . 43
7.5 Prose Anchor Function Services . 43
7.5.1 General . 43
7.5.2 Npanf_ProseKey service . 44
7.5.2.1 Npanf_ProseKey_Register service operation . 44
7.5.2.2 Npanf_ProseKey_Get service operation . 44
7.5.3 Void . 44
Annex A (normative): Key derivation functions . 45
A.1 KDF interface and input parameter construction . 45
A.1.1 General . 45
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A.1.2 FC value allocations . 45
A.2 CP-PRUK derivation function. 45
A.3 Derivation of CP-PRUK ID* . 45
A.4 K derivation function . 46
NR_ProSe
A.5 Calculation of DCR confidentiality keystream . 46
A.6 Calculation of MIC value for discovery message . 46
A.7 Message-specific confidentiality mechanisms for discovery . 47
A.8 Calculation of K for UE-to-Network relays . 47
NRP
A.9 Calculation of MIC value for Direct Communication Request . 47
Annex B (informative): Source authenticity of discovery messages . 49
Annex C (informative): Change history . 50
History . 51

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Foreword
This Technical Specification has been produced by the 3rd Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
In the present document, modal verbs have the following meanings:
shall indicates a mandatory requirement to do something
shall not indicates an interdiction (prohibition) to do something
The constructions "shall" and "shall not" are confined to the context of normative provisions, and do not appear in
Technical Reports.
The constructions "must" and "must not" are not used as substitutes for "shall" and "shall not". Their use is avoided
insofar as possible, and they are not used in a normative context except in a direct citation from an external, referenced,
non-3GPP document, or so as to maintain continuity of style when extending or modifying the provisions of such a
referenced document.
should indicates a recommendation to do something
should not indicates a recommendation not to do something
may indicates permission to do something
need not indicates permission not to do something
The construction "may not" is ambiguous and is not used in normative elements. The unambiguous constructions
"might not" or "shall not" are used instead, depending upon the meaning intended.
can indicates that something is possible
cannot indicates that something is impossible
The constructions "can" and "cannot" are not substitutes for "may" and "need not".
will indicates that something is certain or expected to happen as a result of action taken by an agency
the behaviour of which is outside the scope of the present document
will not indicates that something is certain or expected not to happen as a result of action taken by an
agency the behaviour of which is outside the scope of the present document
might indicates a likelihood that something will happen as a result of action taken by some agency the
behaviour of which is outside the scope of the present document
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might not indicates a likelihood that something will not happen as a result of action taken by some agency
the behaviour of which is outside the scope of the present document
In addition:
is (or any other verb in the indicative mood) indicates a statement of fact
is not (or any other negative verb in the indicative mood) indicates a statement of fact
The constructions "is" and "is not" do not indicate requirements.
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1 Scope
The present document specifies the security and privacy aspects of the Proximity based Services (ProSe) in the 5G
System (5GS). 5G ProSe security features include: 5G ProSe Direct Discovery security, 5G ProSe Direct
communication security, and 5G ProSe UE-to-Network Relay security.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 23.304: "Proximity based Services (ProSe) in the 5G System (5GS)".
[3] 3GPP TS 33.501: "Security architecture and procedures for 5G system".
[4] 3GPP TS 33.303: "Proximity-based Services (ProSe); Security aspects".
[5] 3GPP TS 33.535: "Authentication and Key Management for Applications (AKMA) based on
3GPP credentials in the 5G System (5GS)".
[6] 3GPP TS 33.536: "Security aspects of 3GPP support for advanced Vehicle-to-Everything (V2X)
services".
[7] 3GPP TS 23.503: "Policy and charging control framework for the 5G System (5GS); Stage 2".
[8] 3GPP TS 33.220: "Generic Authentication Architecture (GAA); Generic Bootstrapping
Architecture (GBA)".
[9] 3GPP TS 33.223: "Generic Authentication Architecture (GAA); Generic Bootstrapping
Architecture (GBA) Push function".
[10] 3GPP TS 23.502: "Procedures for the 5G System".
[11] 3GPP TS 33.102: "3G security; Security architecture".
[12] Void
[13] 3GPP TS 23.502: "Procedures for the 5G System".
[14] IETF RFC 7542: "The Network Access Identifier".
[15] IETF RFC 9048: " Improved Extensible Authentication Protocol Method for 3rd Generation
Authentication and Key Agreement (EAP-AKA')".
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3 Definitions of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in 3GPP TR 21.905 [1] and the following apply. A term
defined in the present document takes precedence over the definition of the same term, if any, in 3GPP TR 21.905 [1].
For the purposes of the present document, the following terms given in 3GPP TS 23.304 [2] apply:
5G ProSe Direct Communication
5G ProSe Direct Discover
5G ProSe-enabled UE
5G ProSe Remote UE
5G ProSe UE-to-Network Relay
Direct Network Communication
Discovery Filter
Discovery Query Filter
Discovery Response Filter
Indirect Network Communication
Mode of communication
Model A
Model B
Open ProSe Discovery
ProSe Application Code
ProSe Application ID
ProSe Application Mask
ProSe Query Code
ProSe Response Code
ProSe Restricted Code
Restricted ProSe Application User ID
Restricted ProSe Discovery
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [1].
5G DDNMF 5G Direct Discovery Name Management Function
5G PKMF 5G ProSe Key Management Function
CP-PRUK Control Plane ProSe Remote User Key
AF Application Function
AKMA Authentication and Key Management for Applications
AV Authentication Vector
BSF Bootstrapping Server Function
CP Control Plane
DCR Direct Communication Request
DUCK Discovery User Confidentiality Key
DUIK Discovery User Integrity Key
DUSK Discovery User Scrambling Key
GBA Generic Bootstrapping Architecture
GPI GBA Push Info
GPS Global Positioning System
MIC Message Integrity Check
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NAI Network Access Identifier
NITZ Network Identity and Time Zone
NRPEK NR PC5 Encryption Key
NRPIK NR PC5 Integrity Key
NTP Network Time Protocol
PAnF Prose Anchor Function
ProSe Proximity-based Services
UP-PRUK User Plane Prose Remote User Key
RPAUID Restricted ProSe Application User ID
RSC Relay Service Code
SBI Service Based Interface
UP User Plane
UTC Universal Time Coordinated
4 Overview
4.1 General
The overall architecture for 5G ProSe is given in TS 23.304 [2]. 5G ProSe includes several features that may be
deployed independently of each other. For this reason, no overall security architecture is provided and each feature
describes its own architecture.
Security for the 5G ProSe common procedures is described in clause 5, while the overall security of the 5G ProSe
features is described in clause 6.
4.2 Reference points and functional entities
4.2.1 Functional entities
4.2.1.1 General
Architectural reference model is specified in clause 4.2.1, 4.2.2, 4.2.3, and 4.2.7 of TS 23.304 [2].
4.2.1.2 5G ProSe Key Management Function
In addition to the architectural reference model specified in TS 23.304 [2], the architectural reference model shall
support the functional entity 5G ProSe Key Management Function (5G PKMF) which is the logical function handling
network related actions required for the key management and the security material for discovery of a 5G ProSe UE-to-
Network Relay by a 5G ProSe Remote UE, and for establishing a secure PC5 communication link between a 5G ProSe
Remote UE and 5G ProSe UE-to-Network Relay.
The 5G ProSe Remote UE and the 5G ProSe UE-to-Network Relay know from which 5G ProSe Key Management
Function(s) to get the needed discovery security materials for protecting discovery messages and UP-PRUK(s) for
establishing a secure PC5 link between the 5G ProSe Remote UE and the UE-to-Network Relay as the address of the
5G PKMF(s) is either pre-provisioned or provided by the 5G DDNMF (or the PCF) in the HPLMN of the 5G ProSe
Remote UE to the 5G ProSe Remote UE, and by the 5G DDNMF (or the PCF) in the HPLMN of the 5G ProSe UE-to-
Network Relay to the 5G ProSe UE-to-Network Relay.
The 5G PKMF interacts with the 5G ProSe-enabled UE using procedures over PC8 reference point defined in
clause 4.2.2. The protection for the key request/response messages are described in clause 5.2.5.
The 5G PKMF of the 5G ProSe Remote UE shall request the discovery security materials from the 5G PKMFs of the
potential 5G ProSe UE-to-Network Relays from which the 5G ProSe Remote UE gets the relay services.
The 5G PKMF of the 5G ProSe UE-to-Network Relay shall request the security materials (e.g. Knrp and Knrp freshness
parameter) from the 5G PKMF of the 5G ProSe Remote UE for PC5 communication.
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4.2.1.3 Prose Anchor Function
In addition to the architectural reference model specified in TS 23.304 [2], the architectural reference model shall
support the functional entity Prose Anchor Function (PAnF) which is the logical function handling network related
actions required for the key management and the security material for establishing a secure PC5 communication link
between a 5G ProSe Remote UE and 5G ProSe UE-to-Network Relay over Control Plane.
The PAnF shall store the Prose context info (i.e. SUPI, RSC, CP-PRUK, CP-PRUK ID) for a 5G ProSe Remote UE.
The PAnF interacts with AUSF using procedures over Npc11 reference point defined in clause 4.2.2. The PAnF
interacts with UDM using procedures over Npc12 reference point defined in clause 4.2.2.
4.2.2 Reference points
In addition to the reference points are specified in clause 4.2.5 of TS 23.304 [2], the 5G Prose architectural reference
model shall support the following reference points:
PC8: The reference point between the UE and the 5G ProSe Key Management Function (5G PKMF). PC8 relies on
5GC user plane for transport (i.e. an "over IP" reference point). It is used to transport security material to UEs for
5G ProSe UE-to-Network Relay discovery and communication.
Npc9: The reference point between the 5G PKMF of the 5G ProSe Remote UE and the 5G PKMF of the 5G ProSe
UE-to-Network Relay. It is used to transport security material between two 5G PKMFs.
Npc10: The reference point between the UDM and the 5G PKMF. It is used to de-conceal SUCI to gain SUPI,
obtain a GBA Authentication Vector (AV) for a UE, or request relay service authorization information from the
UDM.
Npc11: The reference point between the AUSF and Prose Anchor Function (PAnF). It is used to store the Prose
context info for a 5G ProSe Remote UE.
Npc12: The reference point between the PAnF and UDM. It is used to check with the UDM whether the Remote
UE is authorized to use the UE-to-Network Relay service.
5 Common security procedures
5.1 General
This clause describes the security requirements and procedures that are commonly applied to different modes of ProSe
communication, including unicast mode ProSe Direct Network Communication and unicast mode ProSe Indirect
Network Communication via the 5G ProSe UE-to-Network Relay.
5.2 Network domain security
5.2.1 General
5G Prose uses several interfaces between network entities, e.g. Npc4 between the 5G DDNMF and the UDM, Npc8
between the 5G DDNMF and the PCF (see TS 23.304 [2]). This clause describes the security for those interfaces.
5.2.2 Security of Npc2 reference point
5.2.2.1 General
Npc2 is the reference point between the ProSe Application Server and the 5G DDNMF as specified in clause 4 of
TS 23.304 [2]. When the ProSe Application Server is in a 3rd party's network, the Npc2 comprises two interfaces, i.e.
the service-based interface between the 5G DDNMF and the NEF, and the N33 interface between the NEF and the
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Prose Application Server. When the Prose Application Server is in a MNO's network, the Npc2 is a purely service-
based interface.
5.2.2.2 Security requirements
When the ProSe Application Server is controlled by a 3rd party, requirements on security aspects of NEF are captured
in clause 5.9.2.3 of TS 33.501 [3].
5.2.2.3 Security procedures
When the ProSe Application Server is controlled by a 3rd party, security procedures specified in clause 12 of TS 33.501
[3] is applicable.
When the Prose Application Server is controlled by a MNO, security procedures specified in clause 13 of TS 33.501 [3]
is applicable.
As specified in TS 23.304 [2], the 5G System architecture supports the service based Npc2 interface between 5G
DDNMF and ProSe Application Server and optionally supports PC2 interface between the 5G DDNMF and the ProSe
Application Server. The security of PC2 reference point specified in TS 33.303 [4] shall be reused.
5.2.3 Security of UE - 5G DDNMF interface
5.2.3.1 General
PC3a is the reference point between the 5G Prose-enabled UE and the 5G DDNMF as specified in clause 4.2.5 of
TS 23.304 [2].
5.2.3.2 Security requirements
3rd parties shall not be allowed to provide configuration data impacting the 5G ProSe-related network operations to the
5G ProSe-enabled UE. The 5G ProSe-enabled UE and the 5G DDNMF shall mutually authenticate each other.
The transmission of the material for 5G Prose discovery between the 5G DDNMF and the 5G ProSe-enabled UE shall
be integrity protected.
The transmission of the material for 5G Prose discovery between the 5G DDNMF and the 5G ProSe-enabled UE shall
be confidentiality protected.
The transmission of the material for 5G Prose discovery between the 5G DDNMF and the 5G ProSe-enabled UE shall
be protected from replays.
5.2.3.3 Security procedures for configuration transfer to UICC
See clause 5.3.3.1 in TS 33.303 [4].
5.2.3.4 Security procedures for PC3a using GBA
For the security procedures for protecting data transfer between the UE and the 5G DDNMF on the PC3a interface, the
use of either TLS v1.2 or TLS v. 1.3, as described in clause 5.3.3.2 in TS 33.303 [4] applies with the following
modifications:
- The ProSe function is replaced by the 5G DDNMF.
- Confidentiality protection shall be enabled.
5.2.3.5 Security procedures for PC3a using AKMA
Security procedures specified in clause B.1.3.2 of TS 33.535 [5] is applicable with the additional changes:
- The 5G DDNMF takes the role of AF.
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- Confidentiality protection shall be enabled.
5.2.3.6 Privacy issue in PC3a interface
PC3a interface will be used to transfer the configuration data that is used to perform 5G ProSe Direct Discovery.
According to clause 6.3.1.4 of TS 23.304 [2], the UE identity is included in the Discovery Request message. Privacy of
UE identity is ensured by the confidentiality protection over PC3a interface.
5.2.4 Security of service-based interfaces used in 5G Prose
5.2.4.1 Security requirements
The 5G Prose network entities shall be able to authenticate the source of the received data communications.
The transmission of data between 5G Prose network entities shall be integrity protected.
The transmission of data between 5G Prose network entities shall be confidentiality protected.
The transmission of data between 5G Prose network entities shall be protected from replays.
5.2.4.2 Security procedures
Npc4, Npc6, Npc7 and Npc8 specified in clause 4.2.5 of TS 23.304 [2] are realized by corresponding NF service-based
interfaces, therefore security procedures specified in clause 13 of TS 33.501 [3] apply to these interfaces.
5.2.5 Security for UE - 5G PKMF interface
5.2.5.1 General
The 5G ProSe-enabled UEs have interactions with the 5G PKMF over the PC8 interface in the ProSe features described
in clause 4.2.2.
5.2.5.2 Security requirements
The 5G PKMF for commercial services and for public safety services provides the security keys and security material
affecting the 5G ProSe-related network operations to the 5G ProSe-enabled UE for discovery of a 5G ProSe UE-to-
Network Relay and PC5 communication with a 5G ProSe UE-to-Network Relay.
The 5G ProSe-enabled UE and the 5G PKMF shall mutually authenticate each other.
The 5G System shall support that the transmission of the security keys and security material between the 5G PKMF and
the 5G ProSe-enabled UE shall be integrity protected.
The 5G System shall support that the transmission of the security keys and security material between the 5G PKMF and
the 5G ProSe-enabled UE shall be confidentiality protected.
The 5G System shall support that the transmission of the security keys and security material between the 5G PKMF and
the 5G ProSe-enabled UE shall be protected from replays.
The 5G System shall support that the transmission of the UE identity on the PC8 interface shall be confidentiality
protected.
5.2.5.3 Security procedures for PC8 using GBA
For the security procedures for protecting data transfer between the UE and the 5G PKMF on the PC8 interface, the use
of either TLS v1.2 or TLS v. 1.3, as described in clause 5.3.3.2 of TS 33.303 [4] applies with the following
modifications:
- The ProSe function is replaced by the 5G PKMF.
- Confidentiality protection sha
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