VoteBox Nano: A Smaller, Stronger FPGA-based Voting Machine

This paper describes a minimal implementation of a cryptographically secure electronic voting system, built with a low-cost Xilinx FPGA board. This system, called VoteBox Nano, follows the same basic design principles as VoteBox, a full-featured electronic voting system. As with VoteBox, the votes are encrypted using Elgamal homomorphic encryption and the accuracy of the system can be challenged by real voters during an ongoing election. In order to fit within the limits of a minimal FPGA, VoteBox Nano eliminates VoteBox's sophisticated network replication and storage facilities. In return, VoteBox Nano runs without any operating systems or language runtime system, radically shrinking the implementation complexity. VoteBox Nano also integrates a hardware true random number generator, providing improved security for the ballot cryptography. In order to deter hardware tampering, which might be done to compromise the random number generator, the FPGA's native JTAG interface can be used to verify the FPGA's configuration. At boot-time, the proper FPGA configuration also displays a random number on the built-in display. Any interaction with the JTAG interface will replace the random number with another one, allowing poll workers to detect election-day tampering, simply by observing whether the number has changed.

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