Study on the support of 256-bit algorithms for 5G
The present document details the following:
- An assessment of threats and potential countermeasures posed due to quantum computing and a resulting assessment of relevant countermeasures in the 5G system.
- An assessment of the timelines for the introduction of any countermeasures, in particular the increase of key lengths to 256 bits. This includes an alignment with the timeline for strengthening asymmetric cryptographic algorithms used in 5G systems.
- An assessment of which parts of the 5G system will be affected and in which way.
- A Study of full entropy 256 bit keys in the 5G key hierarchy, beginning with the permanent pre-shared key. Including a study into modifying the derivation algorithms in order to derive child keys from the 256-bit master key instead of the 128-bit key.
- A study to determine whether a longer MAC is appropriate for 5G.
- A study of the coexistence of different size keys. In 3GPP networks, 256-bit keys in 5G will need to coexist with 128-bit keys in legacy networks or earlier 5G phases. This includes storage of keys and separate key derivation algorithms both on the UE and in the core network.
- A study into the desired number of 256-bit algorithms, e.g. if two 256-bit AKA key generation algorithm sets are needed.
- A study of the desired performance aspects for the new 256-bit algorithms taking into account software and hardware aspects.
- A study of key size negotiation.
- A study into whether the current methods for distribution and refresh of security keys are equally applicable to larger key sizes and can remain the same.
- A study into the Encryption and integrity algorithms that could be needed. This includes 256-bit session/intermediate keys in 5G, may, in some cases, simply entail using larger-key versions of current algorithms, while in other cases new algorithms may need to be chosen altogether.
- Recommendations for suitable requirements for the needed algorithms for use with 256-bit keys and ask ETSI SAGE to provide those algorithms.