In Open-Transactions, both parties have a copy of the "last signed receipt" for any given transaction.
The user forms the receipt and signs it, and then the server countersigns it.
Therefore the server cannot forge your receipt because the server does not have your private key.
When an issuer issues his currency onto an OT server, the server will have a copy of the issuer's "last signed receipt," which includes the server ID and shows the current amount that has been issued.
So the server cannot falsely claim to have a certain currency issued on that server, because the server cannot forge the issuer's signature (in the same way that the server cannot falsify your own receipt, since the server cannot forge your signature.)
The other users cannot forge your signature, nor can they forge the server's signature, nor can they forge the issuer's signature, so they cannot falsely issue units of your currency.
Also, each "last signed receipt" includes the current balance. For example, "My current balance is 100 clams. I am withdrawing 10 clams, and my new balance will thus be 90 clams." This receipt also contains the server ID, as well as the asset type ID, and must be signed by the user before being countersigned by the server. Therefore this is also true for the issuer's last signed receipt, the same as for any other user.
I see, but that's more related to a completely descentralized currency like bitcoin. If i create a centralized currency, it has to be possible somehow to create new "coins" out of thin air and issue them to the system. The question is: what would stop other people (besides the currency creator) from doing it? – Coiner – 2013-08-20T16:33:52.080
oh, sorry I didn't knew this is mean to be a software "Open Transactions", i was thinking you were referring to bitcoin like nets. – kanojo – 2013-08-20T16:42:07.970