As opposed to answering Reddit questions that were formulated after his potential capture by US intelligence, and then later uploaded to the AMA to make the answers appear real-time?
- live video where the person can interact with a live feed e.g. reddit
- social proof, e.g. all his lawyers/friends say that he is ok (the cost to fake this would be too high)
- reading a recent blockchain hash (he did this on the livestream but in general dislikes this method as most people won't understand it)
- reading sports results from recent matches, he did this for some US sports results, this is simpler to understand and verify for most people, stick to higher scoring sports to avoid doubts over enumerating all possibilities
Edit: all of this becomes much more difficult as tech improves because you can CGI someone in real-time. But (!) this is not possible yet.
Really if you don't believe he's alive for the reasons I posted above, it's likely that nothing will convince you!
Our concern is that that would reduce the proof of life to a specific methodology. Key management is complex. Primary proof is social proof, lawyers, Pilger, et al. It would be extremely costly for adversary to create conspiracy involving all these actors.
Take a good look:
Edit: in the twitch stream 1:35:30 he starts talking about it but he doesn't actually read a hash
https://www.reddit.com/r/IAmA/comments/5n58sm/i_am_julian_as...
I see your edit. Can you give an example of a statement that would qualify as proof of life?
Example: commenting on a news event from today.