Brainstorming Anonymous Payments

Following the enquiry from the state of Berlin to allow anonymous payments
[1], I thought it might be an idea to look at existing new new techniques
to provide such services.

Off the top of my head I can think of related technologies:

Payswarm
OpenTransactions
TrueLedger
Loom
Ripple
Bitcoin

There's also lots of crypto work on this topic such as chaumian blinding,
anonymous voting, double spend etc.

Perhaps we can brainstorm some ideas and start a wiki page to represent
where we are in 2013

Given the high concentration of privacy oriented hackers and political
activists in the free state of berlin (e.g. the pirate party control 10% of
the parliament) it may be a great place try to deliver some of the
solutions we've been trying to build over the years ....

[1] http://lists.w3.org/Archives/Public/public-webpayments/2013Feb/0011.html