Is EVM tampering possible?

Bujji Phanikiran (a good friend and inspiration) had the privilege of being the Presiding Officer (probably the youngest in history) in this general election. He is an Electronics and Communication Engineer with ICs in his head and heart. He sent me a mail recently about his experience and comments on working with EVMs.

Q) Is tampering of EVM's possible?
A) Theoretically Yes, but Practically near impossible.

Q) You say theoretically yes. How do we do it?
A) Every automated electronic device has its own processor/controller embedded in itself. So, if you want it to work in a different way all you need to do is just change the program in it as per your needs. Just take out the processor, reprogram it and place it back. As simple as that.

Q) If its as simple as that then why do you say its practically near impossible?
A) Thats because all the Presiding Officers (P.O) conduct a mock poll before the start of an election on the EVMs in their respective polling booth to ensure that the EVM is working properly and seal it using two seals (Green Paper seals & White paper seals) along with special tags placed near the "Close" button. So if you have to reprogram the EVM, you will have to remove those seals (damage) and replace them with the seals of the same numbers and have to forger the signatures of the Presiding Officer along with the Polling Agents. And above all these things they need to bribe a whole lot of people who are involved in maintaining the voting machines after the elections starting from police constables to Collectors. And that as per my personal view is near impossible.
I mean just think about how much man power is used in protecting the machines day in and day out. Think of forgering the signatures and seals of all the Presiding Officers and polling agents, duplicating the paper seals with the numbers and all.
Finally it all boils down to FAITH, faith in your system, your government (the one chosen using ballot boxes), faith in people around you(Cause it is them the lecturers, the teachers, the bank officials, many other government servants who are like me, like you, like your mom or dad or aunt or uncle or... you know people around you).

TRUST YOURSELVES, TRUST EVM!