What, if any, mechanisms prevent unauthorized commands? Asks what measures are taken for spacecraft, although the answer doesn't go much farther than pointing to the What would one need to do in order to hijack a satellite? question on Security.SE.
Similarly, Encryption in radio system asks about whether encryption is used in space, receiving a shuttle answer.

But when did they start using encryption, specifically for probes beyond Earth orbit?

Famously, Luna 9 sent its photos back to Earth in a standard fax format, enabling Jodrell Bank to receive the transmission. Although they were specifically asked by the Soviet Union to do so, clearly no encryption was used.

Encryption was poorly understood and quite the hassle back in the 60s. While that is not the case today, is listening/talking to deep space probes still just an issue of expensive equipment and obscure documentation? If not, when did that change?

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    $\begingroup$ Encryption was not poorly understood in the 60s at all. $\endgroup$
    – GdD
    Nov 3, 2020 at 17:13
  • $\begingroup$ Are you asking only about the radio links with the spacecraft, and not the terrestrial connections between facilities? $\endgroup$
    – DrSheldon
    Nov 3, 2020 at 19:01
  • $\begingroup$ @DrSheldon Not between terrestrial facilities. $\endgroup$ Nov 3, 2020 at 19:04
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    $\begingroup$ I stand by this. Space travel predates fundamental concepts like key exchange and asymmetric encryption. Espionage before that is just silly cipher games. $\endgroup$ Nov 3, 2020 at 21:36
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    $\begingroup$ Note that you can authenticate a message (i.e. ensure both the no modification and the identity of the emitter) without encrypting it (i.e. anyone can read the message and check its authenticity) $\endgroup$
    – Manu H
    Nov 4, 2020 at 20:07


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