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5.2.2 Security threats
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As the sensing service operations are performed among sensing function(s) and sensing entities, if the 5GC does not support sensing service operation authorization, the sensing service operation can be abused.
If the connection between sensing functions is not securely established, an attacker is able to tamper or inject or replay sensing operation messages and the sensing result to be exposed, or sniff the sensing result.
If the connection between sensing entity and sensing function is not securely established, an attacker is able to tamper or inject or replay sensing control messages and sensing data, or sniff the collected sensing data.
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5.2.3 Potential security requirements
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The 5G system shall be able to support mutual authentication between SFs.
The 5G system shall be able to support authorization for sensing service operations.
The 5G system shall be able to support integrity protection, confidentiality protection and replay protection for the connection between sensing entity and SF.
The 5G system shall be able to support integrity protection, confidentiality protection and replay protection for the connection between SFs.
NOTE 2: If there is no interaction between SFs based on architecture defined in SA2, the security requirements between SFs are not needed.
Editor’s Note: More security requirements will be added depends on SA2 progress.
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6 Solutions
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Editor's Note: This clause contains the proposed solutions addressing the identified key issues.
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6.0 Mapping of solutions to key issues
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Editor's Note: This clause contains a table mapping between key issues and solutions.
Table 6.1-1: Mapping of solutions to key issues
Solutions
KI#1
KI#2
KI#Z
#1.1
X
#1.2
X
#1.3
X
#1.4
X
#1.5
X
#1.6
X
#1.7
X
#2.1
X
#2.2
X
#2.3
X
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6.1 Solutions to KI#1
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6.1.1 Solution #1.1: Authorization for sensing service request from AF
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6.1.1.1 Introduction
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This solution addresses Key Issue #1: Security of authorization for sensing service invocation and revocation.
In this solution, the sensing service consumer is assumed to be an external AF. The NEF performs the access authorization by verifying the AF's identity, and the SF performs the service authorization by validating the feasibility and policy compliance of the specific sensing request parameters against network capabilities and operator rules.
Editor’s Note: Whether this solution is applicable only for external AF is FFS.
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6.1.1.2 Solution details
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This solution proposes mutual certificate-based authentication between the NEF and the external AF/sensing service consumer using TLS. Certificate based authentication follows the profiles given in 3GPP TS 33.310 [6], clause 6.1.3a. The identities in the end entity certificates is used for authentication and policy checks.
For the protection of communication between AF/sensing service consumer and NEF, TLS is used to provide integrity protection, replay protection and confidentiality protection for the interface between the NEF and the AF/sensing service consumer. Security profiles for TLS implementation and usage follow the provisions given in clause 6.2 of TS 33.210 [7].
After the authentication, the following procedures are used for authorizing sensing service request.
Figure 6.1.1.2-1: Procedure for sensing service authorization
1. The AF sends sensing service request message to the NEF. The message includes AF ID, OAuth 2.0 token, and sensing service related parameters (e.g., target sensing area, sensing time, sensing accuracy, etc).
Editor’s note: Details of the sensing service related parameters are FFS.
2. NEF performs the authorization check for the sensing service request. This includes:
- validating the OAuth 2.0 token presented by the AF; and
- checking the AF's subscription profile to verify that the AF is entitled to request the sensing service.
If the check fails, the NEF rejects the request with a failure cause.
3. If the AF is authorized by the NEF to request for sensing service, the NEF discovers and selects the SF, and sends the Sensing service request message to the SF. This message includes sensing service related parameters.
4. The SF performs sensing service authorization based on the sensing service related parameters. Specifically, this includes:
- validating the sensing service related parameters against operator-defined service policies (e.g., restricted zones, restricted time); and
- checking if the network has available resources to fulfill the request.
If the authorization fails, the SF rejects the request with a failure cause. The reject message is sent to AF via NEF.
Editor’s note: Other validations performed by SF for sensing service authorization are FFS.
5. After successful authorization, the SF proceeds to execute the sensing service.
6-7. The SF provides sensing results in sensing service response to the AF via NEF.
Editor’s note: Details of the procedures are to be aligned with TR 23.700-14 [2].
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6.1.1.3 Evaluation
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TBD
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6.1.2 Solution #1.2: Authorization for Sensing Service
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6.1.2.1 Introduction
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This solution addresses requirements of key issue #1.
In this solution, existing SBA security framework is reused so that authentication and communication protection among sensing service consumer and NEF/SF can be protected using existing SBA mechanism, for authorization, NRF is deemed as authorization check point, and some specific criteria for sensing, e.g. sensing service, sensing location, is considered for sensing service authorization.
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6.1.2.2 Solution details
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Figure 6.1.2.2 - Authorization for Sensing Service
1. AF sends sensing service request to the NEF. The message includes the AF ID, the requested sensing services and optionally the requested sensing location for the sensing service.
2. The NEF performs SF discovery procedure via NRF.
3. The NEF sends token request the NRF.
4. The NRF performs service authorization, the NRF checks whether the AF is authorized to access the SF, whether the requested sensing services are allowed for the AF, and optionally whether the requested sensing location for the sensing service is allowed.
5. If it is authorized, NRF will issue access token and send it to the NEF, and the access token claim includes AF ID, the allowed sensing services and optionally the allowed sensing location.
6. The NEF sends sensing service request to the SF. The message includes the access token, the AF ID, the requested sensing services and optionally the requested sensing location for the sensing service.
7. After successfully verifying the access token, the SF performs sensing based on the allowed sensing services and optionally the allowed sensing location. The SF sends sensing service response including the sensing result to the NEF.
8. The NEF sends sensing service response including the sensing result to the AF.
Editor’s Note: Details of the procedures are to be aligned with TR 23.700-14 [2].
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6.1.2.3 Evaluation
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TBA
Editor’s Note: The evaluation will be made following SA2 conclusion.
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6.1.3 Solution #1.3: Solution on authorization for sensing service request
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6.1.3.1 Introduction
This solution addresses Key Issue#1 on Security of authorization for sensing service invocation and revocation. Specifically, it addresses the third requirement in KI#1: “The 5G system shall be able to authorize sensing service request from a sensing service consumer”.
According to TR 23.700-14 [2], a sensing service request may be initiated by a sensing service consumer. The authorization on service permission includes two levels:
- The first level of authorization is for service access. When the NEF receives the sensing service request initiated by the sensing service consumer (e.g. an AF), the NEF can determine whether the sensing service consumer is authorized to request the sensing service from the 5GC, according to clause 12 in TS 33.501 [5].
- The second level of authorization is based on the local policy. The Sensing Function may check the Sensing Profile to verify the sensing service request from NEF to determine if a sensing service is allowed.
6.1.3.2 Solution details
Figure 6.1.3.2-1: Authorization for sensing service request
1. The AF requests a service request for sensing. The request may include AF ID, sensing service type (object detection, object tracking, etc), sensing service requirements (e.g. accuracy, latency, etc), sensing service area.
2. The NEF may authorize the sensing service request from the AF by reusing the OAuth 2.0 mechanism in clause 12 of TS 33.501 [5].
3. The NEF may discover and select the candidate Sensing Function(s).
4. If the authorization succeeds, then the NEF sends the sensing service request message to the Sensing Function. The request message may contain AF ID, sensing service area, sensing service type, sensing service requirements.
5. The Sensing Function may authorize the sensing service request based on the local policy. The Sensing Function may check the Sensing Profiles to verify the sensing service request from NEF, which may contain allowed sensing service area, allowed sensing service type, allowed sensing service time duration, etc.
Editor’s Note: Where to store the Sensing Profiles is to be aligned with SA2.
Editor’s Note: The authorization in Sensing Function is to be aligned with SA2.
6. If the authorization succeeds, then the Sensing Function proceeds to execute the sensing service.
7. The Sensing Function sends the sensing results to NEF.
8. The NEF sends the sensing results to AF.
6.1.3.3 Evaluation
TBD.
6.1.4 Solution #1.4: Security of the connection to the Sensing service consumer
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6.1.4.1 Introduction
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This solution aims to address the security requirements in Key Issue #2. In TR 23.700-14 [2], architecture for sensing services is studied to enable the 3GPP network to support sensing service invocation and revocation from the service consumer.
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6.1.4.2 Solution details
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The Sensing service consumer acts as external Application Function (AF) to interact with the network.
If the Sensing service consumer acting as external AF then it only interacts with network via NEF. In this case the security mechanisms in clauses 12 of [5] are reused to provide mutual authentication, authorisation, integrity protection, confidentiality protection and replay protection between Sensing service consumer and the NEF.
Editor’s Note: the architecture need to inline to SA2
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6.1.4.3 Evaluation
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TBD.
6.1.5 Solution #1.5: authorize sensing service request using OAuth-based authorization mechanism
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6.1.5.1 Introduction
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The solution addresses KI#1 to authorize sensing service request from the sensing service consumer
Key issues related to System Architecture to Support Sensing, Authorization and Revocation to Support Sensing Service, and Sensing Result Exposure are studied in TR 23.700-14 [2]. Based on solutions for those KIs, a sensing service consumer may access sensing service from sensing function indirectly via NEF. For example, if the sensing service consumer is external AF, it accesses the sensing function through NEF. The sensing service request may trigger operation or revocation of sensing on specific object in specific area at specific accuracy level during specific time, or subscribe to specific sensing result. Sensing service authorization polices are defined in some solutions, and local policies-based authorization is also discussed in some solutions.
If the sensing service consumer is external AF, as specified in clause 12 of TS 33.501 [5], the NEF shall authorize the requests from AF using OAuth-based authorization mechanism, the specific authorization mechanisms shall follow the provisions given in RFC 6749 [8]. When the NEF supports CAPIF for external exposure as specified in clause 6.2.5.1 in TS 23.501[9], then CAPIF core function shall choose the appropriate CAPIF-2e security method as defined in the sub-clause 6.5.2 in TS 33.122[10] for mutual authentication and protection of the NEF – AF interface.
In general, OAuth 2.0 based authorization can be reused to authorize sensing service request from sensing service consumer.
Editor’s Note: As sensing architecture and procedures, and sensing authorization policies are still under discussion in TR 23.700-14 [2], where to retrieve sensing authorization policies, which network function and how to authorize the content of sensing service request by using OAuth 2.0 based authorization is FFS.
Editor’s Note: the architecture and workflow need to inline to SA2
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6.1.5.3 Evaluation
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Editor’s Note: Each solution should motivate how the potential security requirements of the key issues being addressed are fulfilled.
6.1.6 Solution #1.6: Sensing Service Authorization at the Sensing Function
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6.1.6.1 Introduction
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This solution addresses the potential authorization requirement of Key Issue #1: Security of authorization for sensing service invocation and revocation:
“The 5G system shall be able to authorize sensing service request from a sensing service consumer..”
It is proposed that the Sensing Function performs the authorization of the Sensing Request.
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6.1.6.2 Solution details
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Figure 6.1.6.2-1: Sensing Service Authorization at the Sensing Function
1. It is assumed the Sensing Service Consumer (AF) and the NEF have a security association as described in 3GPP TS 33.501 [5], clause 12 “Security aspects of Network Exposure Function (NEF)”. The Sensing Service Consumer sends a Sensing Service Request to the NEF with the descriptive information e.g. sensing service type (object detection, object tracking, environment sensing, etc.), sensing service requirements (e.g. accuracy, latency, resolution, etc.) and time information when the sensing service is needed (e.g. time for sensing measurement, time for sensing report) etc.
2. The NEF selects a Sensing Function for invoking the Sensing Service and to authorize the request. The NEF sends a Nsf_Sensing _Authorization_Request including the AF ID and the sensing information received from the Sensing Service Consumer to the Sensing Function.
3. The Sensing Profiles are stored in the UDR and the Sensing Function sends a Nudr_Sensing_Profile_Request to the UDR including the AF ID.
Editor’s Note: it depends on SA2 decision whether the Sensing Profiles are stored in the UDR or the Sensing Function.
Editor’s Note: The details of the Sensing Profile are FFS
4. The UDR fetches Sensing Profile Information stored for the AF ID.
5. The UDR responds to the Sensing Function with the Sensing Profile Information of the AF.
6. The Sensing Function performs the authorization of the sensing request from the NEF by verifying whether the information from the Sensing Request matches the information stored in the Sensing Profile for the AF.
If the sensing service authorization is successful, the Sensing Function initiates the sensing procedure with the corresponding NF. If the sensing service authorization fails, the Sensing Function responds the failure to the NEF.
7. The Sensing Function responds to the NEF either with the sensing information result from the sensing procedure, or with a successful authorization response or with an authorization failure response.
Editor’s Note: The messages in step 2 and step 7 need to be aligned with SA2.
8. The NEF forwards the message from the Sensing Function to the AF.
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6.1.6.3 Evaluation
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Editor’s Note: Each solution should motivate how the potential security requirements of the key issues being addressed are fulfilled.
6.1.7 Solution #1.7: Reusing existing mechanism for security of authorization of sensing service
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6.1.7.1 Introduction
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This solution addresses the Key Issue #1 (security of authorization for sensing service invocation and revocation). Authentication, communication security, and authorization aspects for NEF and AF interaction have already been specified in Clause 12 of TS 33.501 [5]. The interface between the sensing service consumer acting as an AF and the NEF, is the same interface whose security is addressed in Clause 12 of TS 33.501 [5].
Editor’s Note: The architecture and workflow needs to inline with SA2.
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6.1.7.2 Solution details
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The security mechanism, specified in Clause 12 of TS 33.501 [5], is reused to address the security requirements of mutual authentication, integrity protection, confidentiality protection, replay protection, authorization for the communication between sensing service consumer and NEF.
Editor’s Note: The authorization of the content of the Sensing Service Request is FFS
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6.1.7.3 Evaluation
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TBD
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6.2 Solutions to KI#2
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6.2.1 Solution #2.1: Security for sensing service operation
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6.2.1.1 Introduction
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This solution addresses Key Issue #2: Security protection for sensing service operations.
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6.2.1.2 Solution details
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The solution proposes a security mechanism to secure the connection between the sensing entity and SF.
For the interface between the sensing entities and SF, the communication between the sensing entity and the SF is secured by the NDS/IP security procedures specified in TS 33.210 [7].
Editor’s Note: Whether the SF is implemented as a single NF or is split into separate NFs is to be aligned with SA2.
Editor’s Note: Whether using direct connection between sensing function and sensing entity for control sensing operation and report sensing data needs to align with SA WG2.
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6.2.1.3 Evaluation
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TBD
6.2.2 Solution #2.2: Security of the connection between Sensing Entity and SF
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6.2.2.1 Introduction
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This solution aims to address Key Issue #2.
This solution to secure the connection between Sensing Entity and Sensing Function (SF). SF is responsible for to handle both sensing service control and sensing data processing.
Editor’s Note: the architecture of SF needs to further align with SA WG2.
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6.2.2.2 Solution details
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The SF supports a direct interface (e.g. Nx interface) to send the sensing service control signalling to sensing entity, and the sensing entity uses the same interface to reply the sensing data to the SF.
In this architecture, the integrity protection, confidentiality protection and replay protection for the connection between sensing entity and SF are offered by:
• IPsec ESP and IKEv2 certificates-based authentication as specified in sub-clause 9.1.2 of [5]. IPsec is mandatory to implement on the Sensing Entity. On the SF side, a SEG may be used to terminate the IPsec tunnel.
• In addition to IPsec, DTLS shall be supported as specified in RFC 6083 [11]. Security profiles for DTLS implementation and usage shall follow the TLS profile given in clause 6.2 of TS 33.210 [7] and the certificate profile given in clause 6.1.3a of TS 33.310 [6]. The identities in the end entity certificates shall be used for authentication and policy checks.
Editor’s Note: Whether using direct connection between SF and sensing entity needs to align with SA WG2.
Editor’s Note: the architecture of SF needs to further align with SA WG2 and the security is FFS.
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6.2.2.3 Evaluation
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TBD.
6.2.3 Solution #2.3: Security protection for sensing service operations between sensing entity and SF
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6.2.3.1 Introduction
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This solution is for security protection for sensing service operations between sensing entity and Sensing Function (SF) Security.
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6.2.3.2 Solution details
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Security between SF (Sensing Function) and sensing entity is same as security procedures for non-service based interface security defined in clause 9 of 33.501 [5] using DTLS/IPsec.
Security profiles for DTLS implementation and usage shall follow the TLS profile given in clause 6.2 of TS 33.210 [6] and the certificate profile given in clause 6.1.3a of TS 33.310 [7].
Editor’s Note: This solution is under the assumption that deployment option is direct connection between sensing entity and SF. Need to update according to sensing architecture progress in TR 23.700-14.
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6.2.3.3 Evaluation
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Editor’s Note: Each solution should motivate how the potential security requirements of the key issues being addressed are fulfilled.
6.X Solutions to KI#X
6.X.Y Solution #X.Y: <Solution Title>
6.X.Y.1 Introduction
Editor’s Note: Each solution should list the key issues being addressed.
6.X.Y.2 Solution details
6.X.Y.3 Evaluation
Editor’s Note: Each solution should motivate how the potential security requirements of the key issues being addressed are fulfilled.
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7 Conclusions
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Editor's Note: This clause contains the agreed conclusions that will form the basis for any normative work.
Annex X:
Change history
Change history
Date
Meeting
TDoc
CR
Rev
Cat
Subject/Comment
New version
2025-08
SA3#123
S3-252869
Skeleton for ISAC Security TR
0.0.0
2025-09
SA3#123
S3-253011
Implemented S3-252693, S3-253012, S3-253013 and S3-253014
0.1.0
2025-10
SA3#124
S3-253728
Included changes from S3-253744, S3 253856, S3-253849, S3-253850. S3-253746, S3-253747, S3-253748, S3-253851,S3-253751, S3-251750, S3-253852, S3-253357
0.2.0
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1 Scope
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The present document identifies potential challenges and requirements for supporting AEAD algorithms specified in TS 35.240 [2], TS 35.243 [3], and TS 35.246 [4] for NAS and AS security (including control and user plane security) in the 6G System, including the following:
- Impact to AS and NAS security
- Key hierarchy and management to support AEAD algorithms
NOTE 1: Key hierarchy includes long term key (i.e. full key hierarchy) for usage of AEAD. Procedure aspects (e.g. AKA framework) are not covered in the present document.
- Negotiation of encryption and/or integrity protection when using AEAD algorithms
- Creation and handling of AEAD algorithm inputs, such as Nonce and Associated Data
Co-existence of AEAD-compatible systems and legacy deployments and algorithms (i.e., only AEAD algorithms or both AEAD and standalone algorithms) is taken into account.
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2 References
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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 35.240 Specification of the Snow 5G based 256-bits algorithm set: specification of the 256-NEA4 encryption, the 256-NIA4 integrity, and the 256-NCA4 authenticated encryption algorithm for 5G; Document 1: algorithm specification
[3] 3GPP TS 35.243 Specification of the AES based 256-bits algorithm set: Specification of the 256-NEA5 encryption, the 256-NIA5 integrity, and the 256-NCA5 authenticated encryption algorithm for 5G; Document 1: algorithm specification
[4] 3GPP TS 35.246 Specification of the ZUC based 256-bits algorithm set: Specification of the 256-NEA6 encryption, the 256-NIA6 integrity, and the 256-NCA6 authenticated encryption algorithm for 5G; Document 1: algorithm specification
[5] 3GPP TS 33.501: "Security architecture and procedures for 5G System".
[6] RFC 5116, “Authenticated Encryption with Associated Data”
3 Definitions and abbreviations
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3.1 Terms
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For the purposes of the present document, the terms given in 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 TR 21.905 [1].
example: text used to clarify abstract rules by applying them literally.
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3.2 Symbols
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For the purposes of the present document, the following symbols apply:
<symbol> <Explanation>
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3.3 Abbreviations
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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].
<ABBREVIATION> <Expansion>
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4 Overview and assumption
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Editor’s Note: This clause gives a brief explanation for background information of this SID, e.g. security assumption, existing algorithm specifications and a brief description of AEAD.
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5 Key issues
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Editor’s Note: This clause contains all key issues identified during the study. Due to the nature of this study, not all issues are derived from security threats but all are essential for the adoption of AEAD algorithms in 6G System.
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5.1 Key issue #1: Algorithm selection
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5.1.1 Key issue details
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The current 5G System uses dedicated algorithms for encryption (NEA0, 128-NEA1, 128-NEA2, 128-NEA3) and integrity protection (NIA0, 128-NIA1, 128-NIA2, 128-NIA3) which are selected independently. This means a given session may use the same or different algorithms for encryption and integrity protection (including NULL), on both AS and NAS layer. Even when using AEAD algorithms that combine encryption and integrity protection, the option to select the NULL algorithm may still be required to signal the use of encryption only or integrity protection only.
Having to support both dedicated encryption and integrity protection algorithms and combined algorithms may complicate implementations without a tangible security benefit. Additionally, providing encryption and integrity protection with a single AEAD algorithm may be preferable in terms of performance to running the dedicated algorithms twice.
Depending on the security policy or scenario, AEAD can provide following protections:
1. Encryption,
2. Integrity protection or
3. Encryption and integrity protection.
When negotiating the AEAD algorithm, it can also be necessary to decide which protections are required.
The key issue is to study following:
- whether AEAD only is sufficient or AEAD and standalone algorithms are required, and
- how to enhance algorithm selection for AEAD algorithms and their protections.
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5.1.2 Security threat
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TBD
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5.1.3 Potential requirements
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Algorithm selection may need an enhancement to support AEAD algorithms.
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5.2 Key issue #2: AEAD algorithm interface
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5.2.1 Key issue details
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One of the advantages of using a combined AEAD mode is that some important security decisions have already been made in the construction of the mode, such as in which order encryption and integrity protection is applied. From SA3 perspective, this means that we don't need to discuss in which order operations are to be applied in PDCP and NAS.
Many different AEAD constructs are available and by using a generic interface, it is possible to treat the AEAD as a black box where the underlying construction is transparent to the user of the interface. One such interface is specified in RFC 5116 [6].
Existing interfaces for encryption and integrity algorithms in Annex D.2 and Annex D.3 of TS 33.501 [5] cannot be used for the new AEAD algorithms directly. This is because the new algorithms combine both operations and also require additional input parameters as described in TS 35.240 [2], TS 35.243 [3], TS 35.246 [4]. For example, in addition to the key and IV, an AAD parameter (as described in TS 35.240 [2], TS 35.243 [3], TS 35.246 [4]) is required to enable flexible partial encryption, the output parameters include both the ciphertext and the MAC.
Consequently, how to set the input parameters for NAS and PDCP needs to be further studied because the existing requirements in clause 6.4.3, 6.4.4, 6.5.1, 6.5.2, 6.6.3, 6.6.4 of TS 33.501 [5] cannot be directly applied.
Existing construction of IV for encryption and integrity algorithms in Annex D.2 and Annex D.3 of TS 33.501 [5] contains a 32-bit COUNT, a 5-bit BEARER, a 1-bit DIRECTION. The entropy for the IV might need to increase from the 38 bits defined by 3GPP. Hence, an extra entropy field called EXTRA_IV of 6 bytes is introduced as described in TS 35.240 [2], TS 35.243 [3], TS 35.246 [4].
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5.2.2 Security threats
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There is a threat to system evolution. For example, if the interface is not designed well from day one, it will not be stable for future enhancements and there can be problems to add new functionality. This will not only increase complexity of the system but will also make it more difficult to analyze from a security perspective, and hence the risk for missing threats increases.
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5.2.3 Potential security requirements
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TBD.
5.X Key issue #X: <Key issue name>
Editor’s Note: This clause contains all the key issues identified during the study. Not all key issues may have security threats due to the nature of this study.
5.X.1 Key issue details
5.X.2 Security threat
Editor’s Note: Place holder for a security threat if any.
5.X.3 Potential requirements
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6 Solutions
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Editor’s Note: This clause addresses potential requirements on procedures and protocols to support AEAD algorithms.
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6.0 Mapping of solutions to key issues
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Table 6.0-1: Mapping of solutions to key issues
Solutions
KI#1
KI#2
KI#3
KI#4
KI#5
1
6.Y Solution Y: <Solution Name>
Editor’s Note: This clause contains solutions for key issues. Not all solutions may have evaluation due to the nature of this study.
6.Y.1 Introduction
Editor’s Note: Each solution should list the key issues being addressed.
6.Y.2 Solution details
6.Y.3 Evaluation
Editor’s Note: Place holder for an evaluation if necessary.
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7 Conclusion
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7.Z Key Issue #Z: <Key Issue Name>
Editor’s Note: This clause contains the agreed conclusions for Key Issue #Z.
Annex A: Introduction to AEAD
A.1 Protection provided by AEAD
The key characteristic of Authenticated Encryption (AE) is that ciphering, and integrity protection are executed in a combined operation. This way, data encryption and authentication can ideally be provided in a single pass. Authenticated Encryption with Associated Data (AEAD) additionally allows for input that is authenticated, but not encrypted. This can be leveraged in use cases where solely data integrity is required while the plain text remains visible for processing.
Additionally, AEAD algorithms allow selective ciphering and integrity protection as needed. If only ciphering is required, it may be possible depending on the AEAD algorithm to only output the ciphertext. If only integrity protection is required, all input data can be processed as associated data. Finally, it is also possible to combine both approaches and provide ciphering and integrity protection for one part of a message while another part is only integrity protected (e.g., because certain message contents need to be accessible in plain text).
The 256-bit cryptographic algorithms specified in TS 35.240 [2], TS 35.243 [3] and TS 35.246 [4] are all based on AEAD1, which also allows for confidentiality protection, integrity protection, and a combined AEAD mode.
Table A.1-1: List of 256-bit cryptographic algorithms
Cryptographic algorithm
•
Snow 5G
AES-256
ZUC-256
Operating mode
Confidentiality
256-NEA4
256-NEA5
256-NEA6
•
Integrity
256-NIA4
256-NIA5
256-NIA6
•
Authenticated Encryption with Associated Data (AEAD)
256-NCA4
256-NCA5
256-NCA6
A.2 Algorithm inputs and outputs
AEAD algorithms can take a unique nonce, a single cryptographic key, plaintext and associated data as inputs. The plaintext is an optional when only integrity protection is required. The associated data is an optional if there is no data which requires only integrity protection.
A.3 Order of operations
When using an AEAD algorithm, important security decisions are already made such that in which order encryption and integrity protection is applied.
Annex X:
Change history
Change history
Date
Meeting
TDoc
CR
Rev
Cat
Subject/Comment
New version
2025-10
SA3#124
S3-253743
Implemented S3-253189, S3-253782, S3-253783, S3-253785, S3-253787
0.1.0
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2 References
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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 33.501: "Security architecture and procedures for 5G system".
[3] IETF RFC 9000: "QUIC: A UDP-Based Multiplexed and Secure Transport".
[4] IETF RFC 9001: "Using TLS to Secure QUIC".
[5] draft-ietf-quic-multipath: "Multipath Extension for QUIC".
[6] IETF RFC 8446: “The Transport Layer Security (TLS) Protocol Version 1.3”.
[7] 3GPP TS 33.210: “Network Domain Security (NDS); IP network layer security”.
[8] 3GPP TS 23.501: "System architecture for the 5G System (5GS)".
[9] 3GPP TS 23.502: "Procedures for the 5G System (5GS)".
[10] 3GPP TS 33.535: "Authentication and key management for applications based on 3GPP credentials in the 5G System (5GS)".
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3 Definitions of terms, symbols and abbreviations
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3.1 Terms
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For the purposes of the present document, the terms given in 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 TR 21.905 [1].
example: text used to clarify abstract rules by applying them literally.
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3.2 Symbols
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For the purposes of the present document, the following symbols apply:
<symbol> <Explanation>
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3.3 Abbreviations
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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].
<ABBREVIATION> <Expansion>
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4 Architecture assumption
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Annex AA in TS 33.501[2] is the starting point of this study.
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5 Key issues
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5.1 Key issue #1: PSK support for MPQUIC TLS
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5.1.1 Key issue details
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In TS 33.501 [1] Annex AA.2, server authentication for MPQUIC/TLS [2], [3], [5] is specified. The scope of this key issue is to cover the PSK-based option for MPQUIC/TLS. Solutions to this key issue are expected to provide the means for enabling the PSK option for MPQUIC/TLS. More specifically, the PSK option refers to TLS 1.3 PSK with (EC)DHE key establishment (psk_dhe_ke), since MPQUIC/TLS [4] uses TLS 1.3 [6] and TS 33.210 [7] prohibits the use of PSK-only mode (psk_ke) in TLS 1.3.
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5.1.2 Security threats
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N/A
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5.1.3 Potential security requirements
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The 5G system shall be able to securely derive, deliver, update, and use the PSK (i.e., TLS 1.3 psk_dhe_ke) between UE and UPF to be used for authentication with MPQUIC/TLS.
5.X Key Issue #X: key issue names
5.X.1 Key issue details
Editor’s Note: This clause is going to capture the key issue detail of a key issue.
5.X.2 Security threats
Editor’s Note: This clause is going to capture the security threat of a key issue.
5.X.1 Potential security requirements
Editor’s Note: This clause is going to capture the potential security requirements of a key issue.
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6 Solutions
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6.1 Solution #1: MPQUIC/TLS using PSK derived from KgNB
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6.X.1 Introduction
This solution addresses Key issue #1 by enabling a secure UP communication channel between the UE and the UPF. The approach leverages the current KgNB to derive a pre-shared key (UPF_PSK) and a corresponding identifier (UPF_PSK ID). The UPF_PSK/ID is delivered to the UPF and then used for a mutual-authentication and key exchange using TLS 1.3 PSK psk_dhe_ke.
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6.1.2 Solution details
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Assumptions and scope:
- UE is registered to the 5GS and has established a KgNB with the network.
- Distribution path for UPF_PSK/ID: AMF/SMF → UPF over N2/N4.
Key derivation and identifiers:
- UE and AMF derive UPF_PSK and UPF_PSK ID using current KgNB.
- Input parameters for the KDF include at least the PDU Session ID and a freshness parameter. UPF_PSK derivation can additionally be bound to the selected UPF identity (e.g., FQDN or IP).
Editor’s Note: Motivation for derivation of UPF_PSK using KgNB is FFS.
Editor’s Note: Handling of UPF_PSK derivation in Xn handover scenario is FFS
Setup procedure (PDU Session establishment):
- UE requests a PDU Session indicating support for MPQUIC/TLS using PSK.
- SMF selects a suitable UPF and provides UE with UPF addressing (e.g., IP, port) and obtains UPF_PSK/ID from AMF.
- AMF derives UPF_PSK/ID from current KgNB. SMF forwards UPF_PSK/ID to UPF via N4.
- Upon successful PDU Session Establishment, UE initiates MPQUIC/TLS with the UPF using UPF_PSK, referencing UPF_PSK ID for UPF to locate and use UPF_PSK to perform mutual authentication with the UE.
UPF_PSK update triggers and handling:
- UE CM-IDLE → CM-CONNECTED transition:
- UE and AMF derive new UPF_PSK/ID.
- AMF/SMF updates the UPF with the new UPF_PSK.
- UE initiates MPQUIC/TLS with the UPF using the new UPF_PSK/ID.
Editor’s Note: applicability of the update trigger condition is FFS.
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6.1.3 Evaluation
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Editor’s Note: Evaluation is FFS
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6.2 Solution #2: PSK derivation bound with MA PDU session
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6.2.1 Introduction
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According to TS 23.501 [8] clause 5.32.6, for steering functionalities based on MPQUIC that apply the QUIC protocol and its multipath extensions, the MPQUIC functionality(ies) in the UE communicates with the associated MPQUIC Proxy functionality(ies) in the UPF. The MPQUIC functionality in the UE and the associated MPQUIC Proxy functionality in the UPF uses the "MPQUIC link-specific multipath" addresses/prefixes for transmitting traffic flows over non-3GPP access and over 3GPP access. The "MPQUIC link-specific multipath" IP addresses/prefixes are allocated by the UPF and provided to the UE via SM NAS signalling. For multiple paths sharing the same TLS tunnel, it is proposed that:
- On the UE side, the PSK is derived by the UE and used by the MPQUIC functionality in the UE.
- On the network side, the PSK is used by the associated MPQUIC Proxy functionality in the UPF. The PSK is derived by the SMF or the AMF which holds the root key for PSK derivation and the derived PSK is delivered to the UPF.
- The PSK is bound with a specific MA PDU session, in which way the old PSK used on authentication for an existing MA PDU session cannot be reused on authentication for a new MA PDU session.
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6.2.2 Solution details
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To bound the PSK with a specific MA PDU session, it is proposed to use an identity which can uniquely identify the MA PDU session on both the UE side and network side as an input parameter for PSK derivation. It can be the PDU session ID or IP address of the MA PDU session, given that both the UE and the SMF have the PDU session ID and IP address of the MA PDU session.
When deriving a PSK in the SMF or the AMF and the UE, the following parameters are used to form the input S to the KDF:
- FC = TBD
- P0 = ID of the MA PDU Session or IP address of the MA PDU Session
- L0 = Length of P0
- P1 = SUPI
- L1 = Length of P1
The input key KEY could be the KAMF or KSEAF or an intermediate key derived from KAMF or KSEAF.
Editor’s Note: The impact on the SMF for key handling is to be captured in the evaluation clause.
The intermediate key derived from KAMF or KSEAF could be the KSMF, which is derived using the following parameters to form the input S to the KDF:
- FC = TBD
- P0 = SMF instance ID
- L0 = Length of P0
The input key KEY could be the KAMF or KSEAF.
Editor’s Note: The use of KSEAF requires the storage of KSEAF. The impact on the legacy handling of KSEAF is to be captured in the evaluation clause.
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6.2.3 Evaluation
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Editor’s Note: This clause is going to capture the pros and cons of the solution, e.g. whether the threats are addressed totally, how the existing 5G system is impacted, whether there is any leftover issues exists, etc.
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6.3 Solution #3: PSK delivery during MA PDU session establishment
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6.3.1 Introduction
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According to TS 23.502 [9] clause 4.22.2, when receiving the UE requested PDU session establishment request with Request Type as "MA PDU Request", the AMF supporting MA PDU sessions selects an SMF supporting MA PDU sessions. It is proposed that:
- When selecting an SMF supporting MA PDU, the AMF sends a key to the SMF for PSK derivation.
The SMF determines to use MPQUIC for the new PDU session based on TS 23.502 [9] clause 4.22.2, then selects and configures the selected UPF supporting MPQUIC. It is proposed that:
- When determining that MPQUIC is to be used for the PDU session, the SMF derives the PSK;
- When configuring the UPF, the SMF provides the derived PSK to the UPF.
On the UE side, when the UE receives a PDU Session Establishment Accept message indicating that the requested MA PDU session was successfully established, the message will include the ATSSS rules for the MA PDU session derived by SMF. If MPQUIC functionality is supported for the MA PDU Session, the SMF will include the "MPQUIC link-specific multipath" addresses/prefixes of the UE and the MPQUIC proxy information that corresponds to the activated MPQUIC-based steering functionality in the ATSSS rules. It is proposed that:
- The UE derives the PSK when receiving the ATSSS rules from the SMF containing the "MPQUIC link-specific multipath" addresses/prefixes of the UE and the MPQUIC proxy information.
- The UE then uses the derived PSK to authenticate with the UPF using MPQUIC/TLS protocol.
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6.3.2 Solution details
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The detailed procedure is shown in Figure 6.3.2-1.
Figure 6.3.2-1: MPQUIC/TLS Security Establishment during MA PDU session establishment
1. The UE provides Request Type as "MA PDU Request" in UL NAS Transport message and its ATSSS capabilities in PDU Session Establishment Request message.
2. Based on Request Type as "MA PDU Request" received from the UE, if the AMF supports MA PDU sessions, the AMF selects an SMF which supports MA PDU sessions. The AMF informs the SMF that the request is for a MA PDU Session by including "MA PDU Request" indication.
In addition, the AMF may send a derived PSK to the SMF or send a root key to the SMF for PSK derivation.
The root key could be the KSMF derived from KAMF or KSEAF.
3. The SMF retrieves, via Session Management subscription data, the information whether the MA PDU session is allowed or not.
4. The SMF returns a Nsmf_PDUSession_CreateSMContext Response to the AMF.
5. The SMF determines the ATSSS capabilities supported for the MA PDU Session taking into consideration the ATSSS capabilities provided by the UE and per DNN configuration on SMF. The SMF initiates an N4 Session Establishment/Modification procedure with the selected UPF. If the MPQUIC functionalities are supported for the MA PDU Session, the SMF instructs the UPF to activate the corresponding functionalities for this MA PDU Session. The SMF receives the UE IP address of the MA PDU session from the UPF.
6. Upon receiving a positive N4 Session Establishment/Modification Response, the SMF derives the PSK from the root key if received from the AMF.
Alternatively, the SMF can also decide to derive the PSK at step #12 after receiving positive PDU session response from the AMF.
If the AMF does not send a root key in step #2, the SMF sends a key request to the AMF/SEAF to acquire the PSK derived by the AMF/SEAF or retrieve the root key before deriving the PSK.
The PSK derivation refers to solution #2.
7. The SMF sends the Namf_Communication_N1N2MessageTransfer message to the AMF.
8. The AMF sends the PDU Session Request message to the gNB.
9. The gNB issues AN specific signalling exchange with the UE that is related with the NAS information received from SMF.
10a. Upon receiving the ATSSS rule in the NAS message from the AMF, if ATSSS rule contains the "MPQUIC link-specific multipath" addresses/prefixes of the UE and the MPQUIC proxy information, the UE determines to derive the PSK from the root key in the same way as the AMF or SMF.
10b. After AN specific signalling exchange with the UE, the gNB returns the PDU Session Response message to the AMF.
11. The AMF sends the Nsmf_PDUSession_UpdateSMContext Request to forward the N2 SM information received from gNB to the SMF.
12. The SMF derives the PSK if not received in step #2 or not derived in step #6.
13. The SMF sends the PSK to the UPF in the N4 Session Modification Request.
14. The UE and UPF perform authenticate using MPQUIC/TLS based on the PSK.
15. The UPF returns the N4 Session Modification Response to the SMF.
Editor’s Note: Key update for reauthentication is FFS.
Editor’s Note: Key derivation and delivery from serving network to home network in roaming scenarios is FFS.
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6.3.3 Evaluation
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Editor’s Note: This clause is going to capture the pros and cons of the solution, e.g. whether the threats are addressed totally, how the existing 5G system is impacted, whether there is any leftover issues exists, etc.
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6.4 Solution #4: Using 5G security context to derive authentication pre-shared key for MPQUIC
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6.4.1 Introduction
|
This solution addresses key issue #1 “PSK support for MPQUIC TLS”.
This solution proposes to derive authentication pre-shared key from the 5G security context to establish the security of MPQUIC for UE and UPF.
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6.4.2 Solution details
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6.4.2.1 The procedure for PSK retrieval
Considering UE and network already generated shared security context during the registration procedure, a sub-level shared key can be generated, and be used as a pre-shared key for MPQUIC.
AMF derives the KUPF from KAMF during the PDU session establishment procedure as shown in the following procedure (Figure 6.4.2.1).
Figure 6.4.2.1 MA PDU session using MPQUIC functionality establishment procedure
1. UE sends PDU session request to AMF which carries an MA PDU request type, PDU session ID and ATSSS capability for the UE as defined in TS 23.502[9].
2-3. AMF selects MA PDU session enabled SMF and forwards PDU session request to SMF as defined in TS 23.502[9].
4. The SMF determines whether the MA PDU session is allowed or not based on operator policy and subscription data, and selects ATSSS enabled UPF as defined in TS 23.502[9]. If the SMF activates MPQUIC functionality, it will derive ATSSS rules and N4 rules for the MA-PDU session as defined in TS 23.502[9].
5. SMF send key request to AMF which carries the UE’s SUPI and PDU session ID,
6. AMF derives KUPF for the UE according to the PDU session ID, generates a KID from PDU session ID and the corresponding UE ID (i.e. SUPI), and sends the KUPF and KID to SMF.
7. Then the SMF initiates the N4 Session Establishment procedure with the selected UPF and sends the KUPF and KID to UPF.
8. The UPF stores the KUPF and the KID for the KUPF.
9. The UPF sends the N4 Session Establishment response message to the SMF.
10-11. Since the UE and the UPF can use certificate or pre-shared key to establish MPQUIC connection. The SMF sends the Using_PSK_indication to the UE in order to inform UE to use PSK for MPQUIC connection establishment.
12. UE derives the key KUPF used for authentication of MPQUIC between UE and UPF according to the Using_PSK_indication and generates KID for KUPF using PDU session ID and its own identifier as defined in clause 6.4.2.4.
13. The UE starts the MPQUIC Establishment procedure to the UPF, and uses KUPF as pre-shared key and KID as the pre-shared key identifier to do the TLS handshake and authentication procedure.
Editor’s Note: roaming scenario is FFS.
Editor’s Note: Key update for reauthentication is FFS.
6.4.2.2 Key hierarchy
The key hierarchy defined in TS 33.501[2] for this scenario can be extended as follows:
Figure 6.4.2.2 Key hierarchy for KUPF retrieval
A new key KUPF is derived from KAMF as depicted in Figure 6. 4.2.2.
6.Y.2.3 KUPF generation
The KUPF is generated by KAMF using the following input parameters.
- FC = 0xXX
- P0 = PDU session ID
- L0 = length of PDU session ID
- P1 = NAS Uplink COUNT value
- L1 = length of NAS Uplink COUNT value
The input key KEY is KAMF.
6.4.2.4 Key ID generation
The Key ID is generated from the PDU session ID and UE ID (i.e. SUPI) as follows:
KID = H(SUPI)|| PDU session ID
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6.4.3 Evaluation
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This solution proposes a solution of deriving authentication pre-shared key from the 5G security context to establish the security of MPQUIC for UE and UPF.
AMF has to derive a key for UPF after SMF determines that MPQUIC functionality will be used and send a request to AMF. UPF has to store the key and the corresponding key identifier in order to use it in the following TLS handshake procedure. For the UE side, KUPF will be derived after the UE receives an Using_PSK_indication indicator from the SMF.
Editor’s Note: further evaluation is FFS.
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6.5 Solution #5: two layer PSK generation method
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6.5.1 Introduction
|
This solution proposes a two layer key generation. The AMF will use KAMF generates a Key KSMF and send the KSMF to the selected SMF. The SMF will further generate KUPF using KSMF, and then deliver the key KUPF to the UPF. Meanwhile, the SMF also generates a key ID, and the Key ID is also sent to the UPF together with the KUPF.
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6.5.2 Solution details
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6.5.2.1 The procedure for PSK retrieval
Figure 6.5.2-1 Procedure to get a PSK between UE and UPF for MPQUIC
1. UE sends PDU Session Establishment Request message to the AMF. The message contains the MAP PDU session information defined in TS 23.502[9] and a PSK capability indication. The PSK capability indication is to indicate that the UE supports to generate a PSK for the MPQUIC/TLS between UE and UPF.
2. The AMF selects a SMF that supports MA PDU as described in TS 23.502[9].
3. The AMF sends Nsmf_PDUSession_CreateSMContext Request. The message includes the MA PDU session information and the PSK capability indication.
4. The SMF decides MPQUIC may be used based on the decision as defined in TS 23.502[9], and knows the UE supporting to generate a PSK based on the PSK capability indication.
5. The SMF request the KSMF by sending a request message to the AMF. The message includes the SUPI of the UE.
6. The AMF generates the KSMF, and sends the KSMF to the SMF in the response message.
NOTE: this solution will not address the message name in step 5 and step6.
7. The SMF uses the KSMF to generate a KUPF and a Key ID.
8. the SMF sends a N4 Session Establishment/modification Response to the UPF. In addition to what is defined in TS 23.502[9], the message further includes the KUPF and a Key ID.
10 – 12. As defined in TS 23.502[9].
13. The UE generates the KSMF, the KUPF and the Key ID the same way as AMF and SMF before the UE starts to use MPQUIC.
14. The UE sends a Client Hello message to the UPF, the message contains the Key ID.
15. The UPF uses the Key ID to retrieve the KUPF. The KUPF is used as the PSK for MPQUIC/TLS.
16. The UPF replies a Server Hello message to the UE.
17. The rest of MPQUIC procedure.
Editor’s Note: roaming scenario is FFS.
Editor’s Note: Key update for reauthentication is FFS.
6.Y.2.2 Key hierarchy
Figure 6.9.2-2 Key hierarchy for KUPF retrieval
Based on the procedure in clause 6.9.2.1, the AMF generates the KSMF by using the KAMF and deliver it to the SMF, and then the SMF uses the KSMF to generate the KUPF that will be further delivered to the UPF.
6.9.2.3 KSMF generation method
The KSMF is generated by KAMF reusing the method in A.13 of TS 33.501[2] with the following updated:
- Set the P0 input parameter DIRECTION to the value 0x02.
6.5.2.4 KUPF generation method
The KUPF is generated by KSMF using the method in A.13 of TS 33.501[2] with the following updated:
- Set the input KEY to KSMF.
- Set the P0 DIRECTION to 0x01.
- Set the COUNT value is set to the value of PDU session ID.
6.5.2.5 Key ID generation method
The Key ID is generated by KSMF using the method in A.3 of TS 33.535[10] with the following updated:
- Set the input key KAUSF to KSMF.
- Set the P0 = "A-TID" to P0 = "UPF Key ID”.
- Set the L0 = length of "A-TID"; (i.e. 0x00 0x05) to L0 = length of " UPF Key ID "; (i.e. 0x00 0x05).
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5242051a01466226d744824c41f583ac
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33.778
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6.5.3 Evaluation
|
The solution considers the backward compatible issue to let the SMF knows whether the UE is upgraded to support generating PSK.
In 3GPP system, all PSKs in the key hierarchy are delivered in one hop only. Thus deliver the PSK to the UPF from SMF is not fully comply with the principle. In case that no new interface is introduced directly between AMF and UPF, it is better the AMF generate a middle key for SMF, and then the SMF generates the key for UPF. The less nodes know the PSK, the better.
The key generation method is based on existing method, the solution proposes to reuse the existing key generation as much as possible. If a parameter can be updated to achieve the goal, then no need to introduce a fully new key generation scheme.
A Key ID is used for UPF to find the right PSK.
This solution needs to change SMF to support storage of KSMF and generation of KUPF and a key ID.
Editor’s Note: Further evaluation is FFS.
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5242051a01466226d744824c41f583ac
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33.778
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6.6 Solution #6: Key derivation and delivery to UE and UPF
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5242051a01466226d744824c41f583ac
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33.778
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6.6.1 Introduction
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The following solutions addresses KI#1 by proposing a mechanism to derive the key inside the 5G core and distribute it to both UE and UPF. Additionally, it proposes a mechanism to initiate re-authentication by deriving and delivering new keys to UE and UPF.
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5242051a01466226d744824c41f583ac
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33.778
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6.6.2 Solution details
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6.6.2.1 Key derivation and distribution
1. A Multi-Access PDU session is established and one or more ATSSS rules require the use of MPQUIC.
2. The UPF request SMF the pre-shared secret for the session with the UE.
3. SMF forwards the Key request to AMF.
4. AMF generates the new key by deriving it from KAMF. The following parameters should be use as input to the KDF:
- FC= 0xWX
- P0= Random Number
- L0= P0 length
5.a. AMF sends a response to SMF containing the generated key.
5.b. AMF send the key and PDU session ID to UE to identify where the correct session to use the key.
6. SMF forwards the response, along with the Key and an identifier of the UE to UPF.
7. UE and UPF authenticate each other and initiate the MPQUIC connection as supported in ATSSS based on the pre-shared secret, i.e., the key.
Editor’s Note: Key derivation and delivery from serving network to home network in roaming scenarios is FFS.
6.6.2.2 Re-Keying mechanism
1. MPQUIC connection has been set up through PSK.
2. Either UE or 5G core requires to renew the pre-shared secret.
3. AMF generates a new key through the same mechanism used during the initial key derivation.
4.a. AMF sends notification of the new Key to UE.
4.b. AMF replies to SMF with the new key.
5. SMF provides the new key to UPF.
6. UE and UPF gracefully terminate the current MPQUIC session.
7. UE and UPF establish a new one based on the pre-shared key.
Editor’s Note: Key update for reauthentication is FFS.
Editor’s Note: The need for a key renewal is FFS.
6.Y.3 Evaluation
The solution completely addresses the problem highlighted by KI#1 both for initial authentication of the connection and for update of the key in case of a compromise. The security is achieved by deriving a new dedicated key for each MPQUIC connection, ensuring that each connection is independently secured, and the compromise of one key will not impact the security of the overall system.
The solution impacts AMF by enhancing its key derivation capabilities to support the new use case. Additionally, it defines delivery mechanism which impact SMF, as both initiator of the procedure and intermediate layer between AMF and UPF, and UPF in the 5G core and the connection towards the UE.
The solution relies on AS security to ensure the confidentiality of the PSK, deactivating the AS security will impact the security of the solution.
Editor’s Note: Further eval is FFS.
6.X Mapping of solutions to key issues
Editor’s Note: This clause is going to capture mapping between key issues and solutions. If there is only one key issue in this study, this clause will be removed.
6.Y Solution #Y: solution names
6.Y.1 Introduction
Editor’s Note: This clause is going to capture the abstract of the solution to address one or more key issues. Which requirements of the key issue shall be included, and what is the key point of the solution is recommended to be listed here as a guidance for the solution details.
6.Y.2 Solution details
Editor’s Note: This clause is going to capture the details of the whole solution, figures and flows are recommended to be used for better understanding the core of the solution.
6.Y.3 Evaluation
Editor’s Note: This clause is going to capture the pros and cons of the solution, e.g. whether the threats are addressed totally, how the existing 5G system is impacted, whether there is any leftover issues exists, etc.
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5242051a01466226d744824c41f583ac
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33.778
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7 Conclusions
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Editor’s Note: This clause is going to capture the conclusions of this study.
Annex A:
Change history
Change history
Date
Meeting
TDoc
CR
Rev
Cat
Subject/Comment
New version
2025.10
SA3#124
S3-253745
The merger of S3-253753,711,712,713,714,715,717,718,415
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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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 TR 23.700-04: “ "Study on Core Network Enhanced Support for Artificial Intelligence (AI)/Machine Learning (ML);”".
[3] 3GPP TS 33.501: "Security architecture and procedures for 5G system".
[4] 3GPP TS 33.535: "Authentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS)".
[5] 3GPP TS 33.210: "Network Domain Security (NDS); IP network layer security".
…
[x] <doctype> <#>[ ([up to and including]{yyyy[-mm]|V<a[.b[.c]]>}[onwards])]: "<Title>".
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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3 Definitions of terms, symbols and abbreviations
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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3.1 Terms
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For the purposes of the present document, the terms given in 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 TR 21.905 [1].
example: text used to clarify abstract rules by applying them literally.
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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3.2 Symbols
|
For the purposes of the present document, the following symbols apply:
<symbol> <Explanation>
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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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].
<ABBREVIATION> <Expansion>
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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4 Overview
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TR 23.700-04 [2] studies transfer of standardized data over UP for UE data collection to meet requirements for AI/ML for NR air interface operation with UE-side model training, all the architecture assumptions and architecture requirements defined in TR 23.700-04 [2] are also applicable to the present document, and any security impact is documented in the present document.
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
|
5 Key issues
|
Editor’s Note: This clause contains all the key issues identified during the study.
5.1 Key Issue #1: Security of UE connection setup with Data Collection NF
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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5.1.1 Key issue details
|
The architecture requirement in clause 4.2 of TS 23.700-04 [2] is that MNO has full controllability and visibility for standardized data. That means the training data between UE and the 5G core will be standardized and it is visible to 5G core and MNO will be data controller.
The key issue aims to address the security issues, such as authentication and authorization for the UE during the connection setup with the data collection network function (Naming and role of data collection function is TBD and subject to progress of TR 23.700-04 [2]). This will ensure only legit and authorized UE are able to share its data towards the Data collection NF.
Another aspect is to address the security issues, ensuring integrity and confidentiality of the UE related data between UE towards the 5GC Data collection NF as studied in KI#1 of TR 23.700-04 [2] to meet requirements for AI/ML for NR air interface operation with UE-side model training.
So, the focus is to identify the means to authenticate and authorize the connection setup between UE and NF before the data transmission take place and to study security of the communication between UE and data collection NF during data transmission.
Editor’s Note: UE to 5GC interaction is ffs depending on progress by SA2.
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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5.1.2 Security threats
|
Lack of authentication and authorization may lead to unauthorized access to network services.
Lack of confidentiality, integrity protection in collecting UE related data can lead to disclosure and tampering of UE related information.
Tampering of UE related data in transit can also impact the quality of training data towards 5GC data collection NF and subsequently to external OTT servers.
Lack of user consent may lead to inadvertent UE data disclosure.
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d0df3e4e3bcefeb18133e59bd2cc2a40
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33.785
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5.1.3 Potential security requirements
|
The 5GS should support authentication and authorization between UE and data collection NF before data transmission takes place.
Editor’s Note: Authentication and authorization between UE and data collection NF is ffs depending on progress on the architecture aspects by SA2.
The 5GS should support confidentiality, integrity and replay protection for data in transit between UE and data collection NF.
The 5GS should support user consent mechanism for data collection by the network depending on the local regulations and operator policies.
Editor’s note: whether user consent is applicable or not will be decided by SA3 based on SA2 progress.
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