How does India ensure the secret ballot?

Secret ballot is ensured in India:
 The voter is given a secret ballot paper by the presiding officer of the polling booth.
 The voter goes behind the curtain to vote to the candidate of one’s own choice.
 Now-a-days, EVM’s (Electronic Voting Machines) are being used in place of ballot
paper.
 The voter presses the button against the candidate of his/her choice with the
symbols assigned to them.
 This maintains the complete secrecy because no one else comes to know to whom
the voter has voted.

Even the candidate does not come to know who has voted him or not.