What's the truth about this "absolutely unbreakable" cipher? A story appeared on Forbes today claiming that we now have an absolutely unbreakable cipher. It cites a paper published in Nature Communications. However, I'm skeptical:


  But what if there were a method of enabling data to be sent using an "absolutely unbreakable" one-time communication technique? What if that technique could achieve perfect secrecy cryptography via correlated mixing of chaotic waves in an irreversible time-varying silicon chip?


That seems like a lot of buzzwords and doesn't sound convincing.


  With no software or code to manipulate, traditional methods of cracking computer encryption are irrelevant





  Again, Dr. Cruz reiterated that there is no code to manipulate, and the limited software is ROM based, so traditional methods of hacking encryption are irrelevant.


Don't ciphers and their weaknesses exist independent of software and code? Solitaire has neither software nor code, but has weaknesses.


  The cryptographic keys generated by the chip, which are used to unlock each message, are never stored


You need the keys to decrypt the message, so even if they're never stored, something good enough to reconstruct them must necessarily be stored.


  It is claimed that even facing an attacker with "unlimited" technological power, even if they could access the system and copy the chips, would be unable to break the encryption because it is protected by the second law of thermodynamics and the "exponential sensitivity of chaos."


I really don't like the sound of this.


  Professor Andrea di Falco of the School of Physics and Astronomy at the University of St. Andrews, another author of the study, said that "this new technique is absolutely unbreakable, as we rigorously demonstrated in our article."


A really extraordinary claim.


  The second law of thermodynamics prevents this attack. Every time Alice and Bob change the chip with an irreversible process, they increase the total entropy of the system and the environment, creating new chaotic structures exponentially different from the ones used in the communication (conditions 3 and 4). If Eve accesses the system, it is impossible to recreate the initial chips and to perform any search, as this requires reverting the transformation of Alice and Bob with an entropy decrease, thus violating the second law.


This is contrary to my understanding of the second law of thermodynamics. Can't you easily decrease entropy in systems that aren't closed (such as the chips), just by increasing it more outside the system (exhaust heat somewhere)?



So is this new cryptosystem legit, or is it just more snake oil? If it's legit, then what are the explanations for my above concerns? If it's snake oil, how did it manage to dupe both Nature Communications and Forbes?
I will go out on a limb here and say that it reeks of snake oil. I have seen the answer by @dirdi, but I am very skeptical. It is clear from the paper that the authors have almost no understanding of cryptography: they refer to algorithms used as DES, AES and RSA, and that quantum computers break them all. 

We know that quantum computers only have quadratic speedup to break symmetric ciphers, to the best of everyone's knowledge. Also the reference to DES, AES and RSA together is very suspect. I quote: "Conventional cryptographic schemes based on DES, AES and RSA encode messages with public and private keys of short length." Huh???

There is no theoretical model for this, like one has for quantum computation (with all of the problems that exist there). Rather, it is more experimental in nature - and we know where that tends to end. Bottom line, this looks really bad and like a lot of other cases where people from other fields think that they can solve all of the world's hard cryptographic problems without knowing anything about cryptography.