Electronic voting should be forbidden for major elections. They are OK in smaller scale, where there is not too much at stake (e.g. your local union or club). I have been involved in designing voting machines but nothing really beats the paper ballot in its simplicity. It is theoretically possible design an electronic voting system using various combinations of public-private key encryption and certificates, but it becomes way too complex. It fails in one fundamental point: the voting system has to be transparent for every Joe Average.