One of the basic problems in electronic documents flow in public administration is authentication of documents and fulfilling all related legal and technical requirements. The situation in public administration is in many ways easier that in general flow of legal documents. Here, the citizens and representatives of public bodies are the actors of the process well defined and known in the system.
A number of technical and legal solutions are aimed to make electronic documents flow easier and more reliable. Out of these, the main components are: electronic seal and personal signature.
In this paper we focus on requirements and their technical feasibility concerning personal signatures. The idea is to provide means for signing documents exchanged between citizens and public bodies so that
1.
immediate disabling of a signature card is possible, and
2.
the signing time is undeniable.
Technical solutions that we propose are based on mediated signatures. In particular, this enables to control ID-card usage against predefined policies (e.g. usage limited to particular time periods, frequency, etc.). In this scenario, a card can be disabled instantly therefore preventing creation of disputable signatures.
In particular, we propose signatures based on hash signatures. For RSA, we propose to embed a deterministic signature based on discrete logarithm problem into padding algorithm. This makes the signatures independent of security of a single algebraic problem.