Recently, I've been musing about cryptographic applications of theoretical future technologies for (breaking) secure interstellar communications. The setting is a video game (Stellaris) featuring several high-tech (mostly) humanoid space-colonizing states in the near future (starting from ~2200) capable of FTL-travel, among other things.

What follows is a list of several 'levels' in scientific advances with cryptographic applications. I'd like to know how realistic these levels are (within the setting as described), and whether there are some important 'levels' I've missed.

  1. (starting tier, supposed to be roughly equivalent to modern widely available crypto) The symmetric AES system (used once keys have been exchanged) and Diffie-Helman on elliptic curves for public key cryptography allow for effective and secure communication over interstellar subspace signal relays, even if they're tapped by nefarious aliens. [Effects: provides encryption for interstellar communication]

  2. (starting tier level minor milestone: side channel attacks) The discovery of side-channel attacks, by which crucial information is extracted from side channels, such as power levels, noise or background radiation, came as a shock to the cryptography community. Quickly, the leading cryptographers constructed systems both to be resistant against side-channel attacks and ways how to exploit unprepared systems. [Effects: provides high resistance again side-channel attacks; can preform side channel attacks on enemies, cheap but with rather low success chance, nearly worthless when facing side-channel resistant systems (but not entirely, there's always a chance of bugs ;^) )]

  3. (near future tier, securing: Applied quantum entanglement) By equipping our ships with special entangled quantum units, we can transfer data without using any conventional medium, making most forms of eavesdropping futile. However, the data-stream is too slow to use for anything except a few emergency signals. (Note that this being actually secure is already fiction, see https://blog.cr.yp.to/20160516-quantum.html) [Effects: simple set of communications is secure against any attacker lacking with tech of level 6 or lower.]

  4. (near future tier, breaking: Applied quantum computing) The result of practical Quantum Supremacy has enabled us to break a whole host of previously secure cryptosystems, by utilizing Grover's and Shor's algorithm. [Effects: can reliably break cryptosystems of level 2 or lower]

  5. (near future tier, securing: Post quantum crypto) (Okay, people are working on this today, but this order makes more sense for the tech-progression here) Fortunately, there are enough systems for which quantum computing gives no significant boost to attackers. By developing them, we can protect our communications once again. [Effects: secure against attackers of level 3]

  6. (future tier: P vs NP) This one's special. Flip a coin. If heads, it turns out that P=NP and we have a practical algorithm for solving NP-hard problems. If tails, it turns out that P!=NP and we have found a one-way functions, enabling the construction of unconditional trapdoor functions. (the coin flip only triggers for the first nation to complete research on P vs NP, all others get the same result) [Effects: If P=NP, all cryptosystems of level 5 or lower, except level 3, are easily broken. Additionally, the fact that most scheduling problems have become easy gives a boost into overall production efficiency. If P!=NP, current communication systems are unbreakable by any crypto of level 5 or lower. Additionally, the fact that NP-hardness is an unconditional lower bound improves research efficiency (due to avoiding various unsuccessful attempts at creating poly-time algos for hard problems)]

  7. (scifi tier, breaking: Entropy reversion) Recent advances in thermodynamics suggest that 'true randomness' doesn't exist and that any so-called 'random' source can be reversed. This makes all conventional cryptosystems useless, as we can simply find out the value of any 'randomly' generated key. (The field of psychology has also been advanced enough to effectively guess keys constructed by sentient beings) [Effects: breaks all crypto of level 6 or lower]

  8. (scifi tier, securing: Precognition) Advances in psionic theory (telepathy, mind-reading and such) have led to the development of 'paired precognition units' that simply know the communications entered in the other pair, no matter how far away (supposedly). So, we're finally able to efficiently and securely 'communicate', by actually not sending any communication signals at all! [Effects: 100% security against any attack of level 7 or lower]

  9. (scifi tier, breaking: interstellar telepathy) Energies from certain rare minerals enable well-trained psi-aware individuals to enhance their powers to read minds light-years away. No cryptosystem can protect the information in the very minds of Alice and Bob. [Effect: breaks all cryptosystems]

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    $\begingroup$ @RonJohn I think the introduction should be compact enough. There is the actual question. The rest is the subject of the question, so to speak. I'm afraid I can't condense the descriptions of the tech-levels while remaining sufficient detail required for the reality check. Are questions of this length generally frowned upon? Should I split this question up into multiple questions? $\endgroup$ – Discrete lizard Feb 19 '18 at 16:33
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    $\begingroup$ Entropy reversion: are you referring to the Comp Sci definition of entropy? $\endgroup$ – RonJohn Feb 19 '18 at 16:44
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    $\begingroup$ Voting to close. This is a badly formed question (this is NOT a discussion forum). Are you asking if, as a group, the "tiers" are sensible or if any individual tier is realistic (#8 and #9 are pure fantasy, how do we judge? based on the reality-check tag, they fail completely) or are you asking something else entirely? The question is neither clear nor specific. SE sites are designed for one question per post (commenting on all 9 tiers is 9 questions). $\endgroup$ – JBH Feb 19 '18 at 17:20
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    $\begingroup$ @RonJohn I could be mixing up Physics definition the one from CS. I think I need the CS one, for it to be relevant for crypto, ultimately. I thought that I could 'break' the physics one to 'break' CS one as a consequence. $\endgroup$ – Discrete lizard Feb 19 '18 at 17:25
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    $\begingroup$ @JBH I admit that I already though this question would be borderline in terms of discussion or opinion based. I'll wait on the (close) votes. Will delete if the community decides it is a bad fit. $\endgroup$ – Discrete lizard Feb 19 '18 at 17:26

One of the tags is "reality-check", and the question mentions "starting from ~2200", which I presume means 180 years from now. Thus, a reality check:

  • Interstellar travel: very unrealistic. Stars are REALLY FAR AWAY.
  • Precognition: very unrealistic. We know all the particles that can interact in the macro world, and none of them can give you a soul or let you locally step above the arrow of time.
  • Interstellar telepathy: see "Precognition".
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  • $\begingroup$ @Raditz_35 we've already launched two probes to the stars. Still, yes you're very optimistic: stars are mindbogglingly far away. $\endgroup$ – RonJohn Feb 19 '18 at 17:00
  • $\begingroup$ I might agree with you if the condition was that the probe actually got there before 2200. But that's all irrelevant and I don't think the intention of the OP who wants subspace communications $\endgroup$ – Raditz_35 Feb 19 '18 at 17:02
  • $\begingroup$ Ah, I'm working within a given setting (the video game Stellaris) which I tried to describe (Although perhaps I should give a better description). I was under the impression that the 'given context' part of reality-check made it appropriate to ask whether something would be realistic wrt. a given fictional setting. $\endgroup$ – Discrete lizard Feb 19 '18 at 17:22
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    $\begingroup$ @RonJohn "we've already launched two probes to the stars." Which ones? That's an honest question. Of the ones we've launched which might qualify, I can think of: two Voyagers, two Pioneers, one New Horizons, and maybe another few that I don't know of off hand. However, with the possible exception of New Horizons, those weren't "launched to the stars". They were designed and launched to study celestial bodies within our solar system. The fact that they have since ventured beyond the distance of Pluto's orbit doesn't change the purpose for which they were launched. $\endgroup$ – a CVn Feb 19 '18 at 18:08
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    $\begingroup$ FTL might or might not be possible. Interstellar travel is definitely doable if you are patient. $\endgroup$ – Donald Hobson Feb 20 '18 at 15:53

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