Editing Scrambler (section)

== Cryptographic ==
It was the need to synchronize the scramblers that suggested to [[James H. Ellis]] the idea for [[Public-key cryptography#Classified discovery|non-secret encryption]], which ultimately led to the invention of both the [[RSA (cryptosystem)|RSA]] encryption algorithm and [[Diffie–Hellman key exchange]] well before either was reinvented publicly by [[Ron Rivest|Rivest]], [[Adi Shamir|Shamir]], and [[Leonard Adleman|Adleman]], or by [[Whitfield Diffie|Diffie]] and [[Martin Hellman|Hellman]].

The latest scramblers are not scramblers in the truest sense of the word, but rather [[Digitization|digitizers]] combined with encryption machines. In these systems the original signal is first converted into digital form, and then the digital data is encrypted and sent. Using modern [[Public-key cryptography|public-key systems]], these "scramblers" are much more [[Security|secure]] than their earlier analog counterparts. Only these types of systems are considered secure enough for sensitive data.

[[Voice inversion]] scrambling can be as simple as inverting the [[Spectral band|frequency bands]] around a static point to various complex methods of changing the inversion point randomly and in real time and using multiple bands. Voice inversion with a fixed frequency offers no security at all and software is available to restore the original voice,<ref>{{cite web |url=https://archive.org/details/unscrambler_202411 |website=Archive.org|year=1999 |title=Voice inversion Unscrambler}}</ref> which is why it is no longer used to protect conversations today. However, voice inversion is still found in low-end Chinese walkie talkies.

The "scramblers" used in [[cable television]] are designed to prevent casual signal theft, not to provide any real security. Early versions of these devices simply "inverted" one important component of the TV signal, re-inverting it at the client end for display. Later devices were only slightly more complex, filtering out that component entirely and then adding it by examining other portions of the signal. In both cases the circuitry could be easily built by any reasonably knowledgeable hobbyist. (see [[Television encryption]].)

Electronic kits for scrambling and descrambling are available from hobbyist suppliers. [[Radio scanner|Scanner]] enthusiasts often use them to listen in to scrambled communications at car races and some public-service transmissions. It is also common in [[Family Radio Service|FRS]] radios. This is an easy way to learn about scrambling.

The term "scrambling" is sometimes incorrectly used when [[Radio jamming|jamming]] is meant.