Kelsey Lewis has been working as a cloud security engineer in a BPO company that provides 24-7 customer service. Owing to the cost-effective storage and security features provided by cloud computing, her organization adopted the cloud environment 4 years ago. Kelsey implemented the TLS protocol to provide security to e-mail communications, voice over IP (VoIP) communication, web traffic, messaging clients, file transfers, and internet services [Domain Name Service (DNS) and Network Time Protocol (NTP)). Which certificate is used by TLS for communication authentication and encryption between hosts?