Assume a blockchain model that contained no transaction data - just pure data. After a set time this data would simply be deleted, and entire blocks would be removed. How would the security model of the blockchain suffer? Would it make it easier for a "long chain" attack, and if so how can this be prevented?
The idea is to store data into the blockchain. Anyone could store data in this chain, and all nodes have a copy of this chain. There is a block race, to secure the blockchain as normal, but there would be no rewards since this is not a money based system. How the deletion is done is yet to be explored, but basically all nodes would agree all blocks older than x months be deleted from their systems.
Would an attacker be able to compute a longer chain if they know of the point at which data is deleted, then show this to the network and then make the network believe this is the correct and valid chain? If so, how can we stop this? (Assume the attacker has less than 51% computing power.) I have looked into timestamps, and time capsule based encryption, but what I want is a mechanism where an attacker cannot successfully create a block without some information that would only be revealed on a specific day.