That is a conceptual question that I am asking here. We are trying to developp an application to securely store the hashes of some files in the blockchain. Everything is automated (taking a file as input, computing the hash, connecting to the Parity Client and calling the notarize function of our contract).
However, we are struggling to answer the question of the accessibility to data: imagine you proceed about 300 transactions per day. If then, from a "proof" point of view, you are asked to retrieve the hash of a given file, how could it be fastly done?
1) We need the Tx hash of the transaction. Thus, we would have to parse every transaction, see the input data, convert to ascii and compare that to a local calculation of the file to be proved. And repeat every step till we find the good input data (if there is one) ---> that's very time consuming and therefore not feasable.
2) Store every detail of every transaction in a DB. But then, we cannot reach our goal, which is to securely store data: integrity of DB can be compromised.
Do you have any clue, about how to build such an access-application? Thank you a lot!