Breaking the encryption scheme of the Moscow internet voting system

Abstract: In September 2019, voters for the election at the Parliament of the city of Moscow will be allowed to use an internet voting system. The source code of it has been made available for public testing. The encryption used in this system is a variant of ElGamal with key sizes that are too small. We explain how to retrieve the private keys from the public keys in a matter of minutes with easily available resources.

Notes:

- Not mentioned in the abstract but the system relies on an Ethereum smart contract.

- The author is a researcher at Loria Nancy (France) which I consider to be one of the best teams in the world on this topic. Among other things he worked on Belenios (http://www.belenios.org/index.html).