![]() This sounds similar to a one-time pad, but it probably wasn't used only once, which means that all encryption became useless if the phonographic record(s) with the noise were stolen. It works by adding noise before transmission and subtracting it on the receiving end. ![]() The only real analog encryption scheme I found was on that Wikipedia page about secure voice communications. Wikipedia's secure voice article only briefly mentions analog signals and then goes on to describe different digital systems. Other sites mention that scramblers were used to prevent television channels from being watched by non-paying consumers, but scramblers have little to do with encryption since they (as the name suggests) are not intended to make the message unintelligible. Upon searching for analog encryption systems I came across DigiCipher (the successor to Videocipher), but it seems to use binary data since Wikipedia mentions that it uses a MPEG-2 compressed stream. To my knowledge, nobody seems to have ever come up with secure and practical ways of encrypting them without converting them to a digital signal first. Good encryption didn't exist until relatively recently (or cryptanalysis would not have been as useful as it was during World War II) while phones and televisions, both using mostly analog signals until the internet came along, have existed for much longer. Bits can be changed so that they appear completely random and map one-to-one back to the original set, given the correct decryption key (and possibly other parameters).īut we always talk about digital encryption, never anything that would work on an analog system as far as I know. I have a basic understanding of how strong encryption works on digital data.
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