"I firmly believe that EVMs (Electronic Voting Machines) are very good machines and cannot be manipulated. The moment we let our NRIs to vote, it has to be a computerised machine without firewalls and then EVMs can be breached.

"But at the moment EVM is like a desktop calculator which is conditioned to perform just two or three functions. So it cannot be hacked," Chawla said at the Kolkata launch of his book "Every Vote Counts: The Story of India's Elections" here.

"I do not think anyone can in anyway change the EVM chips after the votes are cast and change them with other ones. No one can reach those chips using any other external machines.

"Also in the coming elections every single machine will be connected to the VVPAT, which makes the whole system more accountable," he said.

Chawla said the Supreme Court should give its verdict regarding the opposition parties' demand to ensure that 50 per cent EVM results are matched and cross-checked with voter verifiable paper audit trails (VVPATs) before the declaration of the result.

Referring to the electoral system in the US, he said unlike them India has a system of accountability where everybody working in elections are responsible government servants.

"Unlike the American electoral system, where there are different counties who have volunteers coming to conduct the election from the outside, we do not have such a system.

"We have a Chief Electoral Officer in every state, who ensures that every single EVM machine is kept in the custody of the District Magistrates, all of whom are IAS (Indian Administrative Service) officers. The machines go to the polling stations directly from there," he said.

The former CEC, however, refused to comment on the Election Commission's decision to hold polling in seven phases in certain states like Bengal and Bihar, pointing out that the challenges faced by the EC in a particular election cannot be assessed from the outside due to the ever changing scenarios and increase in the number of electorate every year.