Starfleet vessels have security codes (also known as command codes or authorization codes) that can enable or disable various systems on the ship. Do we ever see a character provide the same security code in more than one episode?
Please do not give instances of characters using different codes. This question points out that the codes can be changed. Furthermore, it is quite possible that an officer may have more than one code, each for a different purpose. Therefore, demonstrating that a character uses more than one code proves nothing.