> I'm not sure what security properties are really "proven" about existing cryptographic hash functions AFAIK, we don’t even know whether trapdoor functions ex

> I'm not sure what security properties are really "proven" about existing cryptographic hash functions AFAIK, we don’t even know whether trapdoor functions exist. https://en.wikipedia.org/wiki/Trapdoor_function https://en.wikipedia.org/wiki/Trapdoor_function: “As of 2004, the best known trapdoor function (family) candidates are the RSA and Rabin families of functions” Also note that the ‘examples’ section starts with: “In the following two examples, we always assume it is difficult to factorize a large composite number (see Integer factorization).”