What is LTE encryption?

LTE security is based on a shared secret key K between the USIM and the HSS . The UE, the eNodeB and the MME derive keys for encryption and integrity protection from K. The derived keys are used for: NAS encryption and integrity protection. RRC encryption and integrity protection.

With 4G LTE (and which replaces the legacy Signalling System no. 7 (SS7) protocol), the encryption method used is SNOW 1.0/2.0/3G . These are synchronous stream ciphers developed by Thomas Johansson and Patrik Ekdahl (Lund University). SNOW 3G has been selected for the 3GPP encryption algorithms UEA2 and UIA2.5 Mar 2019

Summary: Calls via the LTE mobile network, also known as 4G, are encrypted and should therefore be tap-proof. … They were able to decrypt the contents of telephone calls if they were in the same radio cell as their target, whose mobile phone they then called immediately following the call they wanted to intercept.