CoffeeCoin is a dummy blockchain with a bootstrap front end. Users can sign-up and generate keys, which are stored in the database file ('dummy' blockchain for a reason). Each user begins with a 100cc in their wallet, which they can transfer to other users who exist in the database. A block with a limit of 5 transactions is mined every 30s (if there are more than 5 transacitons in the memory pool).
The transactions and mining do use public-private key cryptography, hashing and all that jazz.