  The first release of the 5G protocol specifications, 3rd Generation
Partnership Project (3GPP) Release 15, were published in December 2017 and the
first 5G protocol security specifications in March 2018. As one of the
technology cornerstones for Vehicle-to-Vehicle (V2X), Vehicle-to-Everything
(V2E) systems and other critical systems, 5G defines some strict communication
goals, such as massive device connectivity, sub-10ms latency and ultra high
bit-rate. Likewise, given the firm security requirements of certain critical
applications expected to be deployed on this new cellular communications
standard, 5G defines important security goals. As such, 5G networks are
intended to address known protocol vulnerabilities present in both legacy GSM
(Global System for Mobile Communications) networks as well as current LTE (Long
Term Evolution) mobile systems. This manuscript presents a summary and analysis
of the current state of affairs in 5G protocol security, discussing the main
areas that should still be improved further before 5G systems go live. Although
the 5G security standard documents were released just a year ago, there is a
number of research papers detailing security vulnerabilities, which are
summarized in this manuscript as well.
