###### Abstract  
Challenges faced in network security have significantly steered the deployment timeline of Fifth Generation (5G) communication at a global level; therefore, research in Sixth Generation (6G) security analysis is profoundly necessitated. The prerogative of this paper is to present a survey on the emerging 6G cellular communication paradigm to highlight symmetry with legacy security concepts along with asymmetric innovative aspects such Artificial Intelligence (AI), Quantum Computing, Federated Learning, etc. We present a taxonomy of the threat model in 6G communication in five security legacy concepts, including Confidentiality, Integrity, Availability, Authentication and Access control (CIA3). We also suggest categorization of threat-countering techniques specific to 6G communication into three types: cryptographic methods, entity attributes and Intrusion Detection System (IDS). Thus, with this premise, we distributed the authentication techniques in eight types, including handover authentication, mutual authentication, physical layer authentication, deniable authentication, token-based authentication, certificate-based authentication, key agreement-based authentication and multi-factor authentication. We specifically suggested a series of future research directions at the conclusive edge of this survey. communication; security; vulnerabilities; 6G; authentication; threats; countermeasures +
Footnote †: journal: _Symmetry_  
The modern futuristic 6G environment is envisaged in categories such as enhanced Mobile Broad-Band (eMBB), Un-Conventional Data Communications (UCDC), Secure Ultra-Reliable Low-Latency Communications (SURLLC), Three-Dimensional Communications (3 DCom) and Big Communications (BigCom) [9]. Primarily, eMBB comprises multifeatured smartphones, highly dynamic real-world gaming, high-resolution multi-media applications and many more similar applications [10]. However, eMBB lacks symmetry due to huge variations in data rate requirements from a few Mbps to 1 or more Gbps [11]. Moreover, eMBB-based massive bandwidth and huge data impacts the security requirement in terms of an optimized implantation of intrusion detection in Bigdata traversing over the network. Similarly, eMMB also impacts the security in terms of authentication mechanism implementation and cryptographic requirements in low processing devices such as IoTs. Likewise, SURLL covers modern machine tools, smart industry, smart health care, etc., also creating security challenges in authentication and cryptographic processing. 3 Dcom consists of airborne and high-rise smart platforms such as underwater communication, drones, Unmanned Aerial Vehicles (UAVs), etc. [12]. Due to spatiotemporal characteristics of 3 Dcom, the security areas related to availability and confidentiality are most vulnerable. Moreover, drones, UAVs and underwater autonomous systems face limitations related to power-efficient cryptographic processing. UCDC is an open-ended technological edge that covers futuristic smart human bond applications. The dynamic nature of UCDC causes major difficulties related to attribute selection for security implementations such as authentication and confidentiality. Thus, BigCom formulates a holistic communication paradigm at the global level, as illustrated in Figure 1. Moreover, 6G will emerge as a global phenomenon due to futuristic concepts such as mobile fog computing, Unmanned Mobile Systems, blockchain revolutionization, smart cities, etc. [13]. BigCom is a completely unconventional paradigm in mobile communication, resulting in security challenges primarily in the domain of authentication and cryptographic processing. The majority of telecommunication experts consider that the commercialization of 6G will be initiated in 2032 [14]. This 6G multi-dimensional expansion surfaces serious challenges related to threats in cyberspace [15; 16].