Cryptographic theory has provided the notion of provable security which is often an unattainable ideal in practice. Theoretical work gains provable secure protocols only at the cost of efficiency. Theorists are moving from certain primitives towards powerful sets of primitives. That happens because provable secure protocols often have a complex and obscure design, which leads to inefficiency and mistakes. To bridge the gap between cryptographic theory and practice, the random oracle hypothesis was developed. This hypothesis yields crypto protocols much more efficient than standard ones. The article describes the concept of the random oracle model and the replacement of random oracles with hash functions. Practical work shows that no one has been able to perform a successful attack on such crypto protocols.