\section{Results}\label{results}
Currently the Donau REST API is fully implemented. The Donau can manage any
number of charities using the \texttt{/charities} endpoint.
All the keys used for signing and blind signing are managed by the Donau
together with the Secmod helpers.

Overall the Donau is able to issue donation receipts and provide the necessary
donation statement to the donor, all while keeping the data anonymized and
protecting the privacy of the donor. It is also worth mentioning that the
unusual cryptography of blinded signatures does not effect the performance.
With the binding of the tax number to the donation receipts and the signature
of the tax authority with year-dependent keys, the receipts are absolutely
bound to a donor and to a year and cannot be falsified or imitated without
falsifying the signature. Therefore donation fraud can be prevented. By
summarizing the receipts into one single QR-Code, the user convenience for the
tax authority and for the donor could be improved.

Important components that are needed to operate the Donau are not yet
implemented. This includes the charity side and donor client side. The Android
verification app is only partially implemented. Although test where written to
ensure that the Donau endpoints operate as expected, there are still some other
bugs and most likely also unknown bugs, not yet found.

The tax authority emphasizes user convenience and simplicity in a system like
the Donau. The tax authority also mentioned the challenges that arise when
operating such a system in the federalism. Each party often has different
requirements that a system like the Donau should fulfill.
Although the Donau is in its early stages and the prototype has not yet been
deployed, the tax authority Zürich definitely sees potential in the user
convenience side of the Donau.

