Every physical object can be hacked except black holes. Every encrypted message can be decipher except Quantum encryption.

A guy sitting in front of you, can you find out what are the thoughts flooding his brain. The easy approach is just asking him and he will tell you but he may not like to talk to you. Even if he does, he may not speak the truth.
May be, you decide to observe his body language, does he appear nervous, anxious? Is he sitting quietly or biting nails. Of course by such observation, you may guess as to whether he is happy or not, what are his actual thoughts. Using Functional MRI and a remote scanner without his consent one may be able to find out in near future.
Before boring you further let us hasten to add that all the above story is to answer the real question facing Indian democracy and its enthusiasts whether EVM can be hacked or not?
Everything including hacking of EVM or your bank account or Aadhaar details is possible in principle. The only real restrictions being that it should not violate any of the principle of thermodynamics. Hacking EVM does not violate any laws of physics in particular and what is more relevant here is physics because from Informatics point of view the question can be rephrased as to can you get certain information from a system or not. Extracting information need not be through actual direct contact like electrical wire, it could be very well be indirect through information transmitted by it and received by a remote receiver.
Black holes are believed to be the only system from which information may not be or may be impossible to extract, the so called information paradox for black holes. Also Quantum encryption of messages may be the other case in which, it is believed, cannot be deciphered by a hacker.
To understand the above idea in a simple way, let us say in a high school experiment to a boy is asked to measure the temperature of water contained in a beaker. How to proceed to do it, he may sense it by just touching it with fingers, the way a housewife does. But more scientific approach would be to use either a thermometer or some other transducers. Or he can even measure it without coming in contact with the beaker just remotely. For this he needs to detect thermal radiations by the heated water through a radiation type thermometer.
Whenever you measure a quantity it always cause disturbance in the system because energy has to be extracted in the form of information and this disturbs the system. The disturbance may or may not be significant if smaller is the system capacity more the measurement will disturb it or what is commonly called load it. The idea is simple, if to a socket you connect one equipment it is OK but if you try to connect three or four equipment on the same socket using multiconnector, of course it will load the system.
In classical measurement, this loading effect, if necessary can be estimated accurately because although there are random factors affecting it but still it is deterministic in nature however in Quantum measurement it is not possible to estimate it beyond a point because it will violates Heisenberg’s principle of uncertainty.
Except for above esoteric systems, black holes and quantum encryption, information can always be extracted from a system through a suitable means. However when it is done it will always leave an imprint on the system. Just like however perfect a murder is planned and executed it will always leave forensic trail information. Information from EVM like any other system can always be extracted (hack) but it is impossible that such a process will not leave a trail.
Rohit Shukla is a UPSC aspirant, Ashish Kumar Gupta is an IT professional and V. K. Tandon is an Ex-IIT faculty.