After yesterday's discussion about the use of Turing-Complete in exploitation papers, and realizing how commonly the other important term close to my heart, "weird machine", is misunderstood, I wrote a (rather unpolished) blog post about it. addxorrol.blogspot.com/2018/…
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oh boy, for how many years did i want to write (about) this! another aspect many people miss is that TC computation requires the result on the *same* tape, not some subset of it. think about what it means for exploitation ;).
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Same tape vs subset is a slightly different argument (someone would argue that that subset can define a different TM and claim TC on it [infiniteness aside, because the larger tape isn't infinite either]). Ppl just replace "cond branching + ability to change arb memory" with TC
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Replying to @xerub @halvarflake
there's no TC on a finite tape and finite TMs are not at all equal for that same reason. security boundaries are breached when one finite TM breaks out of its own finite tape. i.e., we don't call executing a simpe python script on the python interpreter a security breach per se.

Oct 3, 2018 · 10:58 AM UTC

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Replying to @paxteam @halvarflake
define tape. security boundaries are breached when one finite TM breaks out of its own definition (not merely tape -- tape is just one part of the machine) into another (picture: bigger) finite TM. this differentiation is possible precisely because finite TMs are not at all equal
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tape is what the TM defines as the tape ;). in practice that's *all* storage the given TM has access to. and no, there's no other part of the machine, it's just the tape, everything else lives in some abstract space.
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