# Symmetric key crypto secure communication infrastructure

Imagine that public-key crypto stops working.

Are there any academic proposals out there that would explain how we could implement commercially viable secure communication based on the current infrastructure and symmetric key crypto?

Inspired by this post.

• Please use a spellchecker. Also, the paragraph "Constructing F doesn’t require number theory or any kind of magic. You can basically just start from a bunch of bits and jumble them up in some random way. The trick is just to make sure they are really jumbled, that there wasn’t some pattern that an attacker could exploit" from the post you linked to is a massive understatement. – kodlu Dec 2 '19 at 17:41
• Imagine that public-key crypto stops working. Well if we assume that all public-key cryptosystems would stop working (even the ones that we haven't implemented yet, i.e. supersingular isogeny cryptography, quantum key distribution, etc.) we simply couldn't establish secure communications anymore without physically meeting and sharing a symmetric key. – AleksanderRas Dec 2 '19 at 18:14
• @kodlu I am under the impression that SHA hashing would be an example of such a function $F$ that is currently deemed secure-enough. – Jsevillamol Dec 2 '19 at 18:23
• I think that kodlu was complaining about "some random way" and then checking afterwards. These functions have been designed from start to be secure, they are certainly not thrown together in some haphazard way. – Maarten Bodewes Dec 2 '19 at 19:36