Generate and transfer sealed private key E-Opendime

[opengrid]

Opendime project is a neat solution to off chain bitcoin transfer without the need to put data on the blockchain. It is a physical token and transfer may incur significant costs (well not if bitcoin transaction costs will go into thousands of $).

I'm not a cryptographer but I believe there's a way to generate private key in such a way that I can prove I don't know it and the receiver could cryptographically unseal this private key using certain key and it also can be cryptographically proven a private key was unsealed already.

The best thing I come up with was using a trusted third party confirming that a certain private key might be already unsealed. But introducing a 3rd party is a obvious issue here.