Top-level government direct exchange is often said to proceed via a ‘secure line’ – how is such a line secured?

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Top-level government direct exchange is often said to proceed via a ‘secure line’ – how is such a line secured?

In: Technology

It varies of course but usually it involves something like end to end military grade encryption and only moving the call over infrastructure which is difficult for a listener to compromise, such as military communications satellites or secret fiber optics cables. There is no such thing as communication that is impossible to intercept and decode but it can be made impractically difficult.

If I had to guess –

– It’s end to end encrypted

– It utilizes “dark fiber”. This is optical fiber cable that is owned or leased by a single user. In this case one of the governments

It’s a layered approach of telecommunication technology (equipment and programs).

The message itself is encrypted. The circuits that carry the encrypted packets are connected to boxes that you (allegedly) cannot hack. And then there are intrusion alarms watching for breach into the network.

A communications ‘line’ is ‘secured’, in the sense used in the movies, by introducing additional information that is only known to the parties at the ends of the line *before* the resulting signal enters the uncontrolled public communications network. Therefore, anyone in the middle who snoops at the raw signals flowing back and forth will see information that is ‘obscured’ by some (hopefully) unknown method, a process known more formally as [encryption](https://en.wikipedia.org/wiki/Encryption).

For analog voice it used to rely on a technique generally known as [scrambling](https://en.wikipedia.org/wiki/Scrambler), and there have been [lots of different devices](https://www.cryptomuseum.com/crypto/voice.htm) built in service of that goal over the years. A very early example was the [Scrambler Phone](https://www.cryptomuseum.com/crypto/uk/secraphone/index.htm) which simply ‘rearranged’ the various frequencies that make up the sound of human speech in special pattern known only to the two parties in possession of matching scramblers.

The big evolution was [SIGSALY](https://www.nsa.gov/Portals/70/documents/about/cryptologic-heritage/historical-figures-publications/publications/wwii/sigsaly.pdf), used during World War II and requiring installation of 40 racks containing 55 tons of equipment at each end! It introduced a very early form of digital encryption and relied on both parties possessing a ‘[shared secret](https://en.wikipedia.org/wiki/Shared_secret)’ that was stored on a set of identical analog records.

In modern times, where the ‘line’ between the two parties is some method of digital transport – which includes using a [modem](https://en.wikipedia.org/wiki/Modem) to convert digital information into analog signals for transport over an analog internetwork – [the core concepts are the same](https://en.wikipedia.org/wiki/Alice_and_Bob#History) but the implementation always relies on [rigorous cryptographic methods](https://en.wikipedia.org/wiki/Cryptography#Modern_cryptography) rather than any analog signal manipulation whatsoever.

Nowadays is it usually encrypted voice-over-ip. Basically take the technology that let’s you call Asia for 1c/minute and mash it into the technology that let’s you bank online.