The article by Alex Marquardt provides a detailed guide on configuring security for Elasticsearch, particularly focusing on enabling TLS/SSL encryption and PKI authentication. It emphasizes that as of Elasticsearch versions 6.8/7.1, security features including TLS encryption, user authentication, and role-based access control can be enabled for free. The guide outlines the process of setting up TLS/SSL for both transport and HTTP communications within an Elasticsearch cluster, noting the importance of using appropriate certificates for secure data transmission. For organizations that prohibit storing credentials in configuration files, the article suggests using Public Key Infrastructure (PKI) client certificates as an alternative authentication method. Additionally, it explains how to configure Kibana to authenticate with Elasticsearch using these methods, initially through a username and password, and subsequently through a client certificate approach. The guide provides step-by-step instructions, including generating certificates, modifying configuration files, and testing authentication to ensure secure communication and operation within the Elasticsearch environment.