[Cryptography] [ANNOUNCE] HashCash Digital Cash

[Patrick]

Ashish Gulhati wrote on 06/22/2017 12:31 AM:

> The vault keeps track of spent coins and prevents double spends.
...
> In the case of small transactions (coffee) and micropayments, do we really 
> need to be so paranoid as to shun all trust, and keep hundreds of copies of
> every tiny transaction around forever? Is that even workable at all?

Agreed.  Of course, a HashCash vault would need to keep a record of all
spent coins forever, but that probably isn't a big deal, and at least
it's not tens of thousands of copies stored all over the galaxy.
Moreover, the vault is not spinning its wheels burning huge quantities
of electricity.

If the list of spent coins at one vault somehow reached unmanageable
proportions, the issuer could possibly announce an expiration of that
currency.  Holders of the currency would be required to trade the old
currency for equivalent units of a new currency with a fresh history.
The expiration could be set to occur over a reasonable time frame to
give everyone due notice.  Eventually the record of spent coins in the
old currency could be deleted.

Although I don't think disk space on an individual HashCash vault will
be a pressing consideration, I do think the concept of expiration could
still be important for fiduciary reasons, as it addresses the problem of
"eternal liability" for anyone maintaining a vault containing physical
or digital assets bailed in by users.  Although storage fees can
mitigate the eternal liability problem, the issuer might want to retain
the right to "call in" the issue, demanding redemption within a certain
time frame.  That would give him the option of, say, retiring to spend
time with the grandkids.

All of this is not the concern of HashCash itself, but is just a matter
of contract between the issuer and users.


-- Patrick