My question is not very technical from an implementation point of view, but I am looking for advice to achieve a specific use case using blockchain tech. I would greatly appreciate any insights or advice!
- UserA saves an encrypted file to some off-chain blob storage
- A URI and hash of the encrypted file is stored on chain as proof of existence
- The fact (through some means) that UserA has saved this information is public
- Some other user (i.e. UserB) requests access to UserA's file (potentially in exchange for a payment)
- UserA gives UserB permission to access this file
The problem is that the file is encrypted with UserA's private key. The only way for UserB to gain access to UserA's value after a request and payment has been made is to wait for UserA to become active, see the request, download the file, decrypt it and send it directly to UserB through some other channel.
Is there any way have the file be stored securely, but also accessible to any other user immediately after a payment has been made without UserA's intervention?