Cryptographers achieve perfect secrecy with imperfect devices
&gt;  The universe hadn’t decided what the value would be before it was measured,” said Colbeck. “That’s the origin of the security.”<p>My naive security architect view is, I get the impression the people doing quantum engineering and those working as cryptographers have a very narrow overlap.<p>Reading about quantum key agreement&#x2F;distribution (QKD), it&#x27;s different from cryptographic functions where you have things like convolution and substitution functions, or using hashing to to distribute the information over a very large finite field. The security in quantum appears inseparable from the encoding and implementation itself, which implies there is a proof and description of entropy-in vs. entropy-out that I haven&#x27;t gone deep enough to locate and read yet.<p>I&#x27;d speculate there would be some interesting unification of the Shannon information entropy of a plaintext with physical state thermodynamic entropy of the &quot;enciphered&quot;  Qbits, given transmitting quantum keys like this sounds more like  encoding bits into a physical quantum function than a keyed &quot;encryption&quot; scheme for data for the purposes of security.<p>To do the data exchange, it&#x27;s not <i>encrypted</i> to a key per se, but it sounds more like a lookup table (LUT) over a field of qbit state probabilities. Doing certification of the security of such a system is different from a normal NIST algorithm candidate because it reads like you could write and evaluate the encoding scheme as a proof.