This is the source code repository of the epoint transaction service.

Source
------

web:
	http://nsz.repo.hu/epoint
git:
	git clone git://nsz.repo.hu:45100/repo/epoint


Build
-----

first a recent go build is needed (at least weekly.2012-01-15)
	hg clone http://go.googlecode.com/hg/ go
	cd go/src
	hg update weekly
	./all.bash
(see http://golang.org/doc/install.html for details)

to build and install epoint (into $GOROOT/bin) run
	make


Contact
-------

epoint@nsz.repo.hu - list address
epoint+subscribe@nsz.repo.hu - subscribe
epoint+help@nsz.repo.hu - get help


About
-----

The goal of the epoint service is to provide secure and efficient
bookkeeping of transferrable debt denominated in currencies that
are issued by the anonymous clients of the system themselvs.

The central bookkeeping is designed to be auditable by any client
and proofs can be constructed in case of errors.

To convert between the various currencies a currency market can
be used that is outside of the scope of the epoint service.

The agreements and authentication methods between the issuers and
holders of debt are outside the epoint system as well.

This project originates from the ePoint Transfer Protocol.
Description about that design is at the epointsystem.org website:
	https://www.epointsystem.org/trac/epoint_issuer
	https://www.epointsystem.org/trac/website


Overview
--------

An epoint server is a large billboard, where clients can place
draft documents (acknowledging debt, "i owe you").

Any client can issue debt (issuer), and a client holding the
debt (holder) can transfer parts of it to any other client using
draft documents. A draft specifies the drawer (the client who
transfers the debt), the beneficiary (the new holder of the
debt), the issuer (the client who owes) and an integer amount
that is transferred. The draft is signed by the drawer.

Drafts with different issuers are independent, the debt of
different issuers are denominated in different currencies and
cannot be mixed.

The balance of a client with respect to an issuer is the
agregate value of all the drafts that transfer debt of the given
issuer to or from the given client.

An important constraint of the system is that a holder cannot
transfer more debt than its balance. Such drafts are invalid and
must be rejected. If the issuer is the drawer of a draft then
there is no such constraint. The balance of the issuer is <=0
and the balance of a holder of the issuer's debt is >=0 at any
given time. All the balances together give 0.

The main purpose of the server is to make it easy to check the
current balance of a client.

The server stores all the drafts and the public keys submitted
by the clients so the drafts are verifiable. The ordering of the
drafts matters when the constraints are checked so the balances
are maintained in such a way that there is no ambiguity. Every
change to a balance is recorded in the form of a server signed
certificate. The certificate declares the new balance with a
timestamp and references documents (draft, other certificates
and keys) required to verify the claim. The ordering is
guaranteed by using cryptographic hash references. The hash
chain of documents makes it possible to audit the system and the
signatures allow the construction of proof if the server makes
mistakes.