Gophish and Evilginx are the most applicable choices because the scenario specifically describes acquiring valid credentials through a social engineering campaign. Gophish is a phishing framework used to create campaigns, send phishing emails, manage landing pages, track user interaction, and measure susceptibility to credential-harvesting simulations. Evilginx is a reverse-proxy phishing framework that can relay legitimate authentication flows through an attacker-controlled proxy during an authorized assessment, allowing the tester to evaluate exposure to credential theft and session-token capture techniques, including attacks against some multi-factor authentication workflows. TruffleHog is primarily used to find secrets in repositories or file systems, not to run a social engineering campaign. Shodan identifies Internet-exposed systems but does not perform credential acquisition through phishing. Maltego and theHarvester are useful for OSINT, target mapping, and discovering emails or relationships, but they are preparatory reconnaissance tools rather than primary credential-acquisition mechanisms. Because the question asks for tools and techniques most applicable to obtaining valid credentials through social engineering, Gophish and Evilginx directly satisfy the objective. This maps to study-guide topics covering social engineering, phishing campaigns, credential attacks, adversary emulation, and authorized exploitation workflows.