Would be interesting just to use private/public key with the QSO loggers. ARRL has validation with their LOTW. but that is pretty closed. Would be cool to open this up. Not sure if you need block chain to do it. But would be interesting to have a public ledger that anyone could interact with. and use pub/priv keys for the validation between QSOs. This would be outside of transmitting over RF. If we transmitted keys over RF, we just need to make sure we dont have any issues with "encryption" since in the ham world, that isnt allowed.