# Proven secure scheme under random oracle

Currently I am trying to understand random oracle model in order to make a small presentation about it but I seem to be very confused about it.

Since it's an hypothetical model without a real life application (no function can be completely random), how cryptographic functions are modeled as random oracles (e.g are all hash functions modeled as random oracles?) and how can a cryptographic scheme can be secure under random oracle if there is not concrete proof or implementation of that model?

I think that one difference of standard model with the random oracle model is that is actually secure under some assumptions. Are there any security proofs for random oracle at all?

Can you give an example of a cryptographic protocol/function modeled as an random oracle and one that is not?

Is a hash algorithm an secure under RO until there is a proof that it isn't? (Doesn’t sound very logical).

I have read various sources and most posts from this sitw for random oracle but I didn't find much answers to the ones I stated, so I hope this won't be labeled as duplicate.

Finally, consider a MAC defined by $h(k||m)$. This is secure in the random oracle model but not secure for any Merkle-Damgård based hash function. Thus, there is clearly a separation.