The bizarre claim made in London recently about the alleged hacking of Electronic Voting Machines (EVMs) in previous elections has done more harm than good by diverting public attention from genuine concerns about EVMs and the Election Commission of India’s (ECI) lack of transparency in the matter. The controversy over the security of EVMs dates back to the early 2000s, and is not confined to India. A consensus has emerged that voters can’t verify whether their votes have been recorded and counted correctly, and that miscounts due to EVM malfunction or fraud are undetectable and unchallengeable. Hence, an additional verifiable physical record of every vote cast in the form of voter verified paper audit trail (VVPAT) is required. In 2013, the Supreme Court mandated the use of EVMs with VVPAT units, and ECI has been deploying these in assembly elections from 2017 onwards.
But if a VVPAT-based audit is to have any real security value, it is essential to tally the electronic vote count with the manual one as per the VVPAT slips for a statistically significant sample size of EVMs chosen at random from a suitably defined population of EVMs. Equally important is a clear decision rule about what should be done in the event of a defective EVM turning up in the sample.
But the audit plan that ECI has put in place suffers from serious shortcomings. First, ECI has prescribed a statistically incorrect sample size of just “one polling station (i.e. one EVM) per Assembly Constituency” for all assembly constituencies and all states, even though the number of EVMs in an assembly constituency in different states differs.
Second, ECI has not declared the criteria for arriving at its sample size nor has it specified the population to which this sample size relates. The latter is important because if we assume that 1% of the EVMs are defective, the probability that ECI’s present sample size will fail to detect at least one defective EVM is 99% if “EVMs deployed in an Assembly Constituency” are defined as the “population”. Similarly, the corresponding number is 94% if “EVMs deployed in a Parliamentary Constituency” are defined as the “population”, and varies from about 2% (UP) to 71% (Sikkim) if “EVMs deployed in a state as a whole” are defined as the “population”.