If we search the web for what does encryption mean Wikipedia gives us this definition "In cryptography, encryption is the process of encoding messages or information in such a way that only authorized parties can read it. Encryption does not of itself prevent interception, but denies the message content to the interceptor." So a practical example these days I and my husband use encrypted words, sentences a lot so that my 19 month old daughter does not understand it. Like cucumber is "the long green thing", chicken is "the flying protein" etc :).
Privacy, is the primary aim of encryption. The privacy brings security with it. The end to end encryption means that person/persons to whom the message has been addressed and person/persons giving that particular encrypted message are only the two parties who can see, read the message and no one else while the message is being transferred from a device to another. Whats App, Signal use this end to end encryption method by default. But in case of Telegram one has to choose this option of end to end encryption. In case of end to end encryption no one can read it even in the servers.
The recent Public Interest Litigation on encryption in India
Early May 2016, Sudhir Yadav, a RTI activist, made it to the headlines by filling a petition in the Supreme Court of India demanding the ban of whats App and Telegram and every other messenger application which uses the end to end encryption policy. In his own words, he was not demanding that the whole encryption system to be abolished. On the contrary he was saying the encryption system to be more secure than now i.e 256 bits. But his only innocent urge was that the Government should have the decryption key to that more secure encryption, so that the Government can see, read when it thinks ( and off course without malice, which is sometimes an utopia) that the conversation may threat the national security or of any other super serious matter.
This demand seems to be justified if I think that by possessing the decryption key the Government will be able to protect the national security more efficiently. But if we consider the other aspect, of the personal liberty and secrecy, then comes the doubt. Lets make it simple with a real life example it is something like creating a superbly secured volt but the key of it will be with someone else, who is in a position to take out whatever he feels like. Just think of your mom-in-law who has the key of your cupboard and she can throw out all your dresses just because she thinks it a threat to the family reputation that of her bahu (daughter-in-law) wearing a short dress :).
On 29th June, 2016 a Bench consisting of Hon'ble Justice T.S Thakur, CJI and Hon'ble Justice A M Khanwilkar refused to entertain the aforesaid petition and instead asked him to go to TRAI (Telecom Regulatory Authority of India) with this. And of course with this verdict it is very much clear that SC does not consider whats App and other messaging application usage as a threat to our national security.
The current legal scenario in India:
To know about the present legal situation in India about Encryption please go through this lovely post
Need of Encryption
So,why do we need encryption policy, watch John Oliver