[ohazi]

No, you can't do this in a way that's as strong as conventional encryption. It would be too easy to present your system with an older view of the "ledger" to compel it to reveal expired/locked information. If your system were to mutate some encrypted internal state to keep track of the read count, this could be worked around via backups.

The only way your system could work is if it relied on some sort of TPM, which is essentially security by obscurity.

[alain94040]

Doesn't the blockchain offer some solution to that problem?

[yoha]

No. The blockchain is only a consensus through a network.

Anyone can make a tiny isolated network and create a fork that will look real to the target (here, the iPhone).

This is remotely related to the CAP Theorem [1]. Namely, you expect a blockchain not to fulfill the consistency requirement.

[1] https://en.wikipedia.org/wiki/CAP_theorem