Securing a Redpanda cluster on Kubernetes involves configuring authentication to ensure that the users and clients accessing the API endpoints are verified. The blog outlines various methods to achieve this, such as using SASL, TLS, and mTLS, each offering different levels of security. SASL provides authentication without encryption, while TLS authenticates the server and encrypts communications. mTLS adds an extra layer by requiring mutual authentication between the client and server, making it the most secure but also the most complex to implement. The Redpanda custom resource definition (CRD) in Kubernetes includes four APIs—Kafka API, HTTP Proxy, Schema Registry, and Admin API—each of which can be individually configured for authentication to provide flexibility in securing the cluster. TLS is available for all APIs, offering server authentication and communication encryption, while SASL supports the SCRAM method for the Kafka API. The Redpanda operator utilizes cert-manager to generate necessary certificates for TLS and mTLS, with options for trusted certificate issuers through configuration parameters. Detailed documentation and tutorials are available to guide users through the configuration process, and feedback is encouraged via Slack or GitHub.