🚀 go-pugleaf

Thanks to the people who have sent me information on
DigiCash.  Several people asked for more info, so here
are the address and phone numbers.  Unfortunately, I got
two versions from two different people:

DigiCash			DigiCash
Kruislaan 419			Kruislaan 411
1098 VA  Amsterdam		1098SJ Amsterdam
The Netherlands			The Netherlands

Phone: +31 (20) 665-2611	phone: +31 20 592 2242
Fax:   +31 (20) 668-5486	fax           592 5155

Apparently David Chaum is one of the main people involved.
I found a paper by him and 2 others in the Crypto 88
proceedings which describes an electronic cash system that
sounds like what DigiCash is doing.

You go to the "bank", in this case DigiCash, and withdraw
money by offering a "blinded" random number for them to sign.
You can then unblind the number so that even the bank can't
recognize it, but you can still spend it by showing the
store the bank's signature.  The store then sends the number
back to the bank and gets paid.

The really clever feature is that the bank can't recognize
the numbers as they come in from the stores in terms of who
withdrew them.  That is, it can't unless you try to cheat and
spend the same number twice.  Spending the money involves
going through a little protocol with the store owner, and
some randomness in the protocol ensures that if you do it
twice, you'll reveal enough information that the bank can
figure out who you are.  Then they can sue you, or at least
shut your account down.

I'm looking at several other papers by Chaum on this general
topic and on cryptographic solutions for financial privacy
in general.  His ideas look great, but the papers are complex
and it's going to take me a while to really understand what
he's saying.

Bob Anderson