The advisor gasped and mumbled, "Has Behemoth-19 been hijacked? That's impossible! There was nothing wrong with their authentication tokens!"
Authentication tokens were a special method to determine the status among space pirates. Before their every mission, they would change their authentication tokens and mix them into their messages. Outsiders wouldn't notice anything abnormal.
Only the space pirates could discover the authentication tokens from the messages and decide whether the messages were sent under coercion or at free will.
Authentication tokens could be included in the semaphore, too.