Simplest possible ecash mint

[Nomen Nescio]

How simple can an ecash mint be?

For the simplest case there should be no accounts.  All the mint does is
exchange coins for other coins.  There are no customer lists, no records
of transactions (except as needed for double-spending detection).

The very simplest mint is a pure ecoin changer.  You give it a coin and
it gives you a new one in return.  It checks that the coin you gave it is
valid and has not been spent before.  You also supplied blinding factors
so that the new coin you get is blinded and will not be recognized by
the mint when spent later.

By itself, this trivial mint can support a transaction system, and in
principle a whole economy.  For Alice to pay Bob, she gives him coins.
Bob exchanges them at the mint for new coins, thereby checking that they
are good.  End of transaction.  Bob can spend his new coins elsewhere,
unlinkable to the exchange.

The mint does not even have to be involved in transfers between ecash
and other forms of payment.  This is one of the things the e-gold people
got right.  They outsourced in- and out-transactions.  You go to any of
dozens of coin dealers, currency services, shady operators of all stripes,
to get money into or out of your e-gold account.  The same thing would
work here.  Third parties would offer to buy or sell ecash for dollars,
grams of gold, hi grade cocaine, etc.

As described, this mint has a constant money supply.  There is neither
creation nor destruction of coins.  In practice there would be slow
destruction due to occasional losses of data.  This could lead to very
slow deflation, or the mint could be adjusted to slightly inflate the
currency in order to compensate for this effect.