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272 || AWSAR Awarded Popular Science Stories - 2019
we have now to protect invaluable data? Here comes ‘Cryptography the secure key of future’ to our rescue. In cryptography, we study how we can establish secure communication in the presence of adversaries. Then, the question comes, how can we do that? Let me elaborate byusing famous characters from a Bollywood movie, ‘DilwaleDulhania Le Jayenge’ (DDLJ). Suppose, Simran wants to send a message to her beau Raj while keeping it secret from her suspecting daddy, Baldev. So, in the language of cryptography, they can be designated as the sender (Simran), the receiver (Raj) and the adversary (Baldev). Simran, being smart, converts the message into a new text (known asciphertext) using a secret key of 0 and 1, like 0110110. Simran and Raj have already shared the common key, when they last met in London. She sends this through a general post (non-secure medium) to Raj. Raj converts the ciphertext into the original message by using the common key (it could
have been different keys as
well, in a general scenario).
During the whole process,
even if Baldev intercepts the
message, he ends up getting a
ciphertext, which is of no use,
because Baldev doesn’t have
the secret key used by Simran
and Raj. Hence, the ship
between Simran and Raj can
grow to its logical conclusion.
The whole credit goes to
the processes of encryption
(message to ciphertext) and
decryption (ciphertext to
message). Nowadays, many
smartphones come with the option, ‘Encrypt Phone’.Cryptographyplaysamajorroleinour national security also and hence, it is a major priority for organizations like DRDO (Defence Research and Development Organisation), ISRO (Indian Space Research Organisation)
and NIA (National Investigation Agency). Generally, a cryptographer uses a cipher to disguise his message. Cipher is a stepwise procedure to perform encryption and decryption. Cryptography has a long history. Julius Caesar used encryption to protect messages of military significance. Hence, his method of encryption is known as Caesar’s cipher in which letters in the alphabet would be shifted by a fixed number of spaces to give an encoded message. He used a shift of three to encode his messages. For example, with a shift of three, ‘A’ would be replaced by ‘D’, ‘B’ would become ‘E’ and so on. Intriguingly, in World War II, Enigma cryptosystem was incorporated by the German military intelligence. RSA is one of the first and very famous public-key cryptosystem named after its developers Ron Rivest, Adi Shamir and Leonard Adleman, who also won the Turing award (recognized as Nobel Prize of Computing) in 2002. Some of the famous ciphers that are used by Google are Advanced Encryption Standard
(AES),ChaCha, and Salsa.
At the heart of this complex world of ciphers is the magic of mathematics. Ciphers are based on very difficult problems of mathematics such as prime factorization (don’t worry, I will explain), discrete logarithm (it’s okay, if you don’t know it) and nonlinear equations (they can be related to the linear equations, we studied in school). Suppose you have been asked to factorize ‘91’, you may say that it is fairly simple and it factorizes as ‘13x7’. Every positive integer number (except 1) can be written as a product of primes, for example, 8 can be written as 2 to the power 3. But what if you have to factorise a number that has thousands of digits? This
The growing number of EVs, will raise the demand for an orderly charging strategy.While random charging of scale electric vehicles, in time, will increase the influence of uncertain factors in power grid operation, which will bring new challenges for the economic operation of the power grid scheduling.