Design a web portal that allows entry only after a code issued by an administrator. Use one-time or time-limited codes, server-side verification, and encrypted transmission. Implement input validation, CAPTCHA, and rate limiting to reduce brute-force and enumeration attacks. Store codes using secure hashing and strict expiration policies to prevent reuse. Require HTTPS, strong session handling, and audit logs for issuance and access events. Provide an administrator interface for issuing and revoking codes, and include clear recovery and testing procedures for deployment.
