L.4 Bidding down attack

33.2203GPPGeneric Authentication Architecture (GAA)Generic Bootstrapping Architecture (GBA)TS

To avoid a bidding down attack (also called downplay attack), the 2G GBA solution requires that a GBA-enabled terminal that supports SIM based 2G GBA must support also USIM/ISIM based 3G GBA as specified in I.2.4. If a USIM/ISIM is available, then the terminal must use the USIM/ISIM based 3G GBA as specified in I.4.8.

Annex M (normative):
GBA_Digest