Comunicação scrambling é uma coisa que já existe. Essencialmente, é uma maneira de garantir a privacidade das transmissões de dados, voz ou vídeo. Em Star Trek, como no mundo real, eles usariam isso para proteger suas transmissões de informações confidenciais ou privadas.
Da página de respostas para embaralhamento de comunicação.
Analog voice-scrambling methods typically involve splitting the voice frequency spectrum into a number of sections by means of a filter bank and then shifting or reversing the sections for transmission in a manner determined by switch settings similar to those of a combination lock; the reverse process takes places at the receive end. Digital methods first convert the analog voice to digital form and then scramble or encrypt the digital voice data by one of the methods discussed below. See also Analog-to-digital converter; Electric filter.
A simple data-scrambling method involves the addition of a pseudorandom number sequence to the data at the transmit end. Devices using this method are known as stream ciphers. A second method partitions the data into blocks. Data within a block may be permutated bit by bit or substituted by some other data in a manner determined by the switch setting, which is often called a key. Devices using this method are known as block ciphers. See also Cryptography.
Typical video scrambling devices used for cable television applications involve modifying the amplitude or polarity of the synchronization signals, thereby preventing the normal receiver from detecting the synchronization signals. A more sophisticated technique, used in satellite transmission, introduces a random delay to the active video signal on a line-by-line basis. An even more advanced technique called cut-and-rotate has been proposed. Video signals can also be digitized by a number of coding techniques and then scrambled by any of the data-scrambling techniques discussed above to achieve high security. See also Closed-circuit television.
Read more: http://www.answers.com/topic/communications-scrambling#ixzz2wE3fZ9vc
Obviamente, em Star Trek eles usariam meios mais avançados para embaralhar suas informações, mas geralmente é apenas uma forma de criptografar informações.