Reputation and security

We need such thing as reputation in blockchain system, in smart contracts, in distributed systems. What is reputation? It’s digit representation of all good or bad action of user in the ecosystem. Reputation is not a transferable, and it’s not tradable.

So how we can implement not transferable (and not tradable) reputation with low (but relatively acceptable) security level?

Non-transferrable reputation token can be implemented as a smart contract having identities -> primary key mapping as one to one relation: one identity — one primary key. This smart contract will also have a reputation balance as another mapping to the identities. The reputation balance can be increased or decreased, but reputation can not be less than zero (because of game theory implications). If reputation become less than zero, identity just dies: the user loses the possibility to use identity and has to create a new one.

To use the reputation users MUST tie identity to some temporary key (so that will be another identity -> temp_key mapping). The temporary key can have expire time (in timestamp or in blocks count). Only temporary key can be used in operations with user reputation. If a temporary key was compromised, then user can revoke that temporary key. With a primary key a user can sign infinite counts of temporary keys.

The rationale behind the design is to keep the primary key in cold storage and the temporary key in hot wallet or on server app sending requests to that smart contract.