Question: Which of the following EPS Encryption Algorithms (EEAs) is **not** mandatory for implementation on both User Equipment (UE) and eNodeB (eNB) for RRC signaling and UP ciphering, but is optional?
Option 1: 128-EEA1 SNOW 3G based algorithm
Option 2: 128-EEA2 AES based algorithm
Option 3: 128-EEA3 ZUC based algorithm
Option 4: EEA0 Null ciphering algorithm
Explanation: According to the security architecture specifications, UEs and eNBs are required (shall) to implement EEA0, 128-EEA1, and 128-EEA2 for both RRC signaling ciphering and UP ciphering. However, implementation of 128-EEA3 is optional (may) for these entities in the context of RRC signaling and UP ciphering, highlighting its non-mandatory status in this specific scenario.