Yeah, but effectively that's what Your Mother was asking for, a counterexample for the thesis that multidimensional hashes are safe.

Hence a "proof" according to you. ;)

update

to elaborate more: every example proofs something, but not every proof needs an example.

Or in formal notation:

Example => Proof

So of course YM's "aka" is not correct in mathematics.

But in IT it's important to see how likely a problem is, because nothing is without risk.

For instance the same problem might be easily solved with multidimensional keys, where hashes of hashes have a higher risk to run out of space or to be vulnerable of bugs because of higher algorithmic complexity.