3GPP TS 33.310 V18 — NDS; Authentication Framework

Q: What does the Scope section cover in 3GPP TS 33.310 V18 — NDS; Authentication Framework?

The Scope section provides detailed technical specifications, security considerations, and implementation guidance as documented in 3GPP TS 33.310 V18 — NDS; Authentication Framework. This content is part of the BLACKLABS 3GPP Security Library.

Q: What does the References section cover in 3GPP TS 33.310 V18 — NDS; Authentication Framework?

The References section provides detailed technical specifications, security considerations, and implementation guidance as documented in 3GPP TS 33.310 V18 — NDS; Authentication Framework. This content is part of the BLACKLABS 3GPP Security Library.

Q: What does the PKI Architecture section cover in 3GPP TS 33.310 V18 — NDS; Authentication Framework?

The PKI Architecture section provides detailed technical specifications, security considerations, and implementation guidance as documented in 3GPP TS 33.310 V18 — NDS; Authentication Framework. This content is part of the BLACKLABS 3GPP Security Library.

Q: What does the Certificate Management section cover in 3GPP TS 33.310 V18 — NDS; Authentication Framework?

The Certificate Management section provides detailed technical specifications, security considerations, and implementation guidance as documented in 3GPP TS 33.310 V18 — NDS; Authentication Framework. This content is part of the BLACKLABS 3GPP Security Library.

Q: What does the Certificate Profiles section cover in 3GPP TS 33.310 V18 — NDS; Authentication Framework?

The Certificate Profiles section provides detailed technical specifications, security considerations, and implementation guidance as documented in 3GPP TS 33.310 V18 — NDS; Authentication Framework. This content is part of the BLACKLABS 3GPP Security Library.

BLACKLABS

3GPP TS 33.310

Network Domain Security (NDS); Authentication Framework

V18.2.0 (2024-06) — Release 18 33-Series Security

1. Scope

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This specification defines the PKI-based authentication framework for NDS/IP. It specifies certificate profiles, management procedures, and trust models for X.509 certificates used in IPsec (IKEv2) and TLS authentication between 3GPP network elements.

TS 33.501 clause 13.1 requires mutual TLS authentication using certificates profiled in this document. All SBI TLS certificates and all NDS/IP IPsec certificates follow the profiles defined here.

2. References

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Ref	Document	Title	Link
[1]	IETF RFC 5280	Internet X.509 PKI Certificate and CRL Profile	RFC 5280
[2]	IETF RFC 6960	OCSP	RFC 6960
[3]	IETF RFC 6712	CMPv2 over HTTP	RFC 6712
[4]	IETF RFC 4210	Certificate Management Protocol (CMP)	RFC 4210
[5]	IETF RFC 8446	TLS 1.3	RFC 8446
[6]	3GPP TS 33.210	NDS IP network layer security	Local

4. PKI Architecture

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┌──────────────┐ │ Root CA │ (offline, air-gapped) │ (self-signed)│ └──────┬───────┘ │ ┌────────────┼────────────┐ ▼ ▼ ▼ ┌──────────────┐ ┌──────────────┐ ┌──────────────┐ │ Sub-CA (TLS) │ │ Sub-CA (IPsec)│ │ Sub-CA (SEPP)│ │ for SBI NFs │ │ for SEGs/NEs │ │ for N32 │ └──────┬───────┘ └──────┬───────┘ └──────┬───────┘ │ │ │ ┌────┼────┐ ┌────┼────┐ ┌────┼────┐ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ AMF SMF NRF SEG-A SEG-B gNB SEPP-v SEPP-h

Root CA: Trust anchor — should be offline and heavily protected
Sub-CAs: Issue end-entity certificates; may be per-purpose (TLS vs IPsec vs SEPP)
End-Entity Certificates: Used by NFs, SEGs, NEs for TLS/IPsec/N32 authentication
Certificate enrollment: Via CMPv2 (RFC 4210) or EST (RFC 7030)

5. Certificate Management

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Operation	Protocol	Description
Initial Enrollment	CMPv2 / EST	NE requests first certificate from RA/CA
Renewal	CMPv2 / EST	Before expiry, NE requests new certificate signed with existing key
Re-key	CMPv2 / EST	New key pair generated, new certificate issued
Revocation	CMPv2 (rr)	CA revokes certificate; published via CRL or OCSP
Recovery	CMPv2	Key recovery for key-escrow scenarios (not recommended for auth keys)

Automated enrollment and renewal are critical. Manual certificate management does not scale in 5G with thousands of NFs and gNBs. CMPv2 or EST must be deployed.

6. Certificate Profiles

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6.1 NF TLS Certificates (SBI)

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Field	Requirement
Key Algorithm	ECDSA P-256 (preferred) or RSA ≥2048-bit
Signature Algorithm	ecdsa-with-SHA256 or sha256WithRSAEncryption
Subject	NF Instance ID or NF FQDN
SAN (Subject Alt Name)	DNS name of the NF service; may include NF Instance ID as URI
Key Usage	digitalSignature, keyEncipherment (for RSA)
Extended Key Usage	id-kp-serverAuth, id-kp-clientAuth (for mutual TLS)
Validity Period	Operator-defined; recommended ≤1 year
CRL Distribution Points	Required — URL of CRL or OCSP responder

6.2 IPsec/IKEv2 Certificates

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Field	Requirement
Key Algorithm	ECDSA P-256 or RSA ≥2048-bit
Subject	SEG/NE FQDN or IP address
SAN	IP address (for IKEv2 IDr) or FQDN
Key Usage	digitalSignature
Extended Key Usage	Not required for IKEv2 (per RFC 7296)

6.3 SEPP N32 Certificates

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SEPP certificates for the N32 interface require special handling:

Inter-PLMN trust: Cross-certified CAs or pre-provisioned trust anchors
PLMN ID must be verifiable from the certificate (SAN or Subject)
Certificate used for both N32-c (TLS) and N32-f (JOSE JWS signing)
GSMA PKI may provide inter-operator trust anchors

7. Certificate Revocation

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Method	Mechanism	Latency	Use Case
CRL	Periodic download of revocation list	Hours (CRL update interval)	Low-frequency environments
OCSP	Real-time revocation check (RFC 6960)	Real-time	5GC NFs (preferred)
OCSP Stapling	Server includes OCSP response in TLS handshake	Cached (staple lifetime)	High-performance SBI

OCSP or OCSP stapling is preferred for 5GC. CRL-only revocation can leave a window where compromised certificates remain trusted.

8. Trust Model

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Scenario	Trust Model	Trust Anchor
Intra-PLMN (same operator)	Single PKI hierarchy	Operator's Root CA
Inter-PLMN (roaming)	Cross-certification or GSMA bridge CA	Pre-provisioned peer CAs or GSMA PKI
Non-3GPP access (N3IWF)	Operator PKI for IPsec; public PKI for UE-side WiFi	Mixed: operator + public