1. You can hack into the DSN, and try to do it that way.
2. Set up an 80-meter dish in your back yard, with a team of NASA RF experts.
With step (2), the authorities will zero in on you in a second, so the emphasis is definitely on the cyber security of the ground infrastructure and not on SSL-over-space-link-communication.
Not just assembling the dish - you also have to know the ephemeris schedule, bit coding scheme (it changes based on circumstances), packet formats, software infrastructure... In the great scheme of things, my friend, Cuba or Zimbabwe secretly erecting an 80 meter dish just to f--k with a rover on mars isn't really a concern. Even though ESA or China or Japan might conceivably have the theoretical capability to do this... there are other things to worry about.
2. Set up an 80-meter dish in your back yard, with a team of NASA RF experts.
With step (2), the authorities will zero in on you in a second, so the emphasis is definitely on the cyber security of the ground infrastructure and not on SSL-over-space-link-communication.