You misunderstand, I meant a public blockchain. People have been using the bitcoin and ethereum blockchain to store proof of existence for ages now, see stamp.i

You misunderstand, I meant a public blockchain. People have been using the bitcoin and ethereum blockchain to store proof of existence for ages now, see stamp.io You could create an ethereum based registry fairly simply where people paid to be included. I'm definitely addressing both technical and people problems here. Apart from that, I'm sorry, the practicalities of crypto-currency have been debated ad nauseum and I don't feel like arguing them today. :(