// e) Check expiration / feature flags if (payload.IsExpired) return RegistrationResult.Expired; if (!IsFeatureAllowed(payload)) return RegistrationResult.NotAuthorized;
// Windows: DPAPI ProtectData (CurrentUser) // macOS: Keychain // Linux: libsecret or encrypted file with file‑system ACLs
// f) Persist securely SaveLicenseSecurely(payload); finecam registration code
// a) Sanitize input string cleaned = SanitizeKey(userInput); if (cleaned == null) return RegistrationResult.InvalidFormat;
// b) Basic structural validation (e.g., groups of 4 chars) if (!IsCorrectStructure(cleaned)) return RegistrationResult.InvalidFormat; // e) Check expiration / feature flags if (payload
// Trim, upper‑case, remove whitespace/hyphens as needed // Return null if characters outside allowed set are found
// 2. Helper functions -------------------------------------------------------- private string SanitizeKey(string input) if (cleaned == null) return RegistrationResult.InvalidFormat
// 3. Secure persistence ------------------------------------------------------ private void SaveLicenseSecurely(LicensePayload payload)