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SA3 closes its AEAD study

TR 33.771 asked how 6G should use authenticated-encryption (AEAD) algorithms that encrypt and integrity-protect in one pass. SA#113 in Madrid approved the study with all four key issues concluded, which clears the way for normative work.

In 60 seconds

  • Concluded: SA#113 approved TR 33.771 with all key issues concluded (per 6G Futures).
  • What it covers: a new combined-mode family, 256-NCA4/5/6, alongside encryption-only 256-NEA4/5/6 and integrity-only 256-NIA4/5/6.
  • Four key issues: algorithm selection, a common AEAD interface, key derivation and mandatory user-plane integrity.
  • Also approved at SA#113: a new SA3 study on ISAC security and privacy.
SASA3 · TR 33.771

What AEAD changes

In 5G, ciphering (NEA) and integrity protection (NIA) are separate algorithms with separate keys. An AEAD algorithm does both in one operation with one key. That makes integrity protection of user-plane data easier to require, where 5G leaves it optional.

The study examines three 256-bit families built on the three existing cipher bases, SNOW, AES and ZUC:

FamilyFunction
256-NCA4/5/6Combined AEAD: encryption + integrity
256-NEA4/5/6Encryption only
256-NIA4/5/6Integrity only

Rapporteur: Li Hu (vivo). The work item, FS_AEAD, is led by Yuto Nakano (KDDI).

SASA3 · key issues

The four questions SA3 had to answer

  • KI#1 – Algorithm selection: AEAD only, or AEAD coexisting with the standalone NEA/NIA algorithms? And how does the network negotiate which one protects which traffic?
  • KI#2 – AEAD interface: one standard set of input and output parameters, so specifications do not depend on which AEAD algorithm is underneath.
  • KI#3 – Keys: AEAD uses a single key, but the 5G key hierarchy derives two (one for ciphering, one for integrity). How should the key be derived?
  • KI#4 – Authenticated encryption: should integrity protection of encrypted user-plane data become mandatory?

The report carries 27 candidate solutions. Solutions 1 to 6 extend the NAS and AS Security Mode Command procedures that negotiate algorithms. Solution 12 is a full scheme for selecting AEAD algorithms and protecting traffic. Solution 21 defines generic AEAD algorithm parameters.

SASA#113 · 15–18 Sep, Madrid

Approval, and what comes next

Concluded

The report went to SA#113 as v2.0.0 (for approval). 6G Futures reports it was approved with all key issues concluded.

Also agreed

A new SA3 study on the security and privacy of integrated sensing and communication (ISAC). SA#113 also named “secure by design” one of the key principles guiding 3GPP’s 6G work.

This builds on Release 19, which decided to add 256-bit AES, SNOW 5G and ZUC-256 alongside the 128-bit algorithms (see Edition 21). According to 3GPP Highlights, the 256-bit algorithm specifications go into TS 35.240 to TS 35.248.

Watch next

  • Normative CRs: the approved conclusions should turn into Security Mode Command and key-derivation changes. The first place to watch is the SA3 meeting in Prague (12–16 Oct).
  • KI#4: whether 6G makes user-plane integrity mandatory. That is the conclusion with the largest effect on device and network design.

Sources

Report contents are read from FriendlySpec renders of the draft TRs. Drafts change at every meeting; nothing in a draft TR is agreed until its conclusions are. The approval is as reported by 6G Futures.