l wireless technologies and NR V2X will continue to maintain very high standards for V2X security. 3GPP has been developing capabilities that will benefit V2X, starting with enhancements in LTE to support V2X use cases. 5G will evidently support more advanced use cases; therefore, two require- ments are particularly important: (1) the need for direct, ad hoc, broadcast, secure communica- tion without any a priori configuration of security by the network and (2) management of identities for user privacy from the network or other third parties. There are two types of LTE transport-level security mechanisms: (1) LTE security protecting the UE signaling and commu- nications with the LTE network, and (2) LTE D2D or ProSe communications security. LTE security uses a symmetric keying scheme for data protection between the UE and the network. For user-plane data, only confidentiality (encryption) is applied; there is no integrity protection on application-layer messages exchanged with the network. For ProSe/D2D communications, each group of devices conduct one-to-many, confidentiality protected data transfers. This is done using a group symmetric key, which is provisioned by the network to all member devices. There is no integrity protection on the user data and, because the key is shared by all, there is no way to positively identify which of the group members has sent the data. V2X sidelink communication uses the following identities [6]: Source layer-2 ID: Identifies the sender of the data in the sidelink and V2X sidelink communications. The source layer-2 ID is 24 bits long and is used together with desti- nation layer-2 ID and LCID for identification of the RLC UM entity and PDCP entity in the receiver. Vehicle-to-Everything (V2X) Communications 839 Destination layer-2 ID: Identifies the target of the data in the sidelink and V2X sidelink communications. For sidelink communication, the destination layer-2 ID is 24 bits long which is split in the MAC sublayer into two bit strings. The first bit string is the least si