Is there a zero knowledge proof which demonstrates that Peggy knows a value v whose hash-function is w?
In my understanding of the general theorems on zero-k there EXISTS such a function if the has-function has polynomial time complexity. However, I would like to know how such the protocol would look like for the case of SHA-256. My problem is, that the usual proof requires me to reduce the fact of having a certain SHA-256 to Graph 3 Coloring, for example, and I do not see how this could be done practically.
