That I don’t know the answer too. And i would like more information about how it works. I am mostly familiar with Crypto in block chains work and I still wouldn’t say i fully understand that either.
I am also a little confused when they say unchanging. Sure block chain are unchanging but I am assuming you can add new data that would take priority of old data. I don’t think you would want a system that you could never change your key once you add it. Because that is stupid keys can and will get compromised eventually.