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What is Cryptography?

Crypto-what?!

Crypto-Graphy! But, what is cryptography? Could it be a cryptic new branch of graph theory? Could it be the password to the HashThat team's secret hide-out? Could it be the name of the our pet Egyptian two-legged red-white macaw (scientific name: Hashiticus Thatae)? Or is it some fancy jargon we concocted?

Wonder no more! Presenting: "Cryptography: the Art of Secrecy!"

Derived from the Greek words 'κρύπτω' (hidden) and 'γράφω' (write) which are transliterated as 'krύptō' and 'grάfō' respectively, cryptography is essentially the art of camouflaging messages and transferring them safely over to the recipient. This could be anything from using secret codes to hold cross-classroom paper-chit-conferences during lectures to 'encrypting' data relayed over satellites. In the light of today's advancements in cryptography, it is no longer just an art, but also the 'mathematics' and science of protecting information.

Let's get started with an example to understand what cryptography is. Meet Alice and Bob, the protagonists in our example and, in general, in several works on cryptography. Alice decides to send Bob a secret message. Eve, the eavesdropper, is sniffing out all messages Alice is sending out and Alice isn't aware of it. Now when Alice sends her secret message to Bob, Eve will be able to intercept it. The secret message is now in the hands of an adversary, the consequences of which could be catastrophic.

To visualize the gravity of the issue, assume you are Alice and you have a bank account with 'Bank of Bob'. You would like to transfer money out of your account over the internet using the bank's website and you are required to send your credit-card information to Bob for this purpose. While sending this over, if Eve gets hold of this information, the aftermath is apparent.

The solution: Cryptography! Alice 'encrypts' the secret message using cryptographic schemes and sends it over to Bob who then has to 'decrypt' this to get back the original message. Eve, in the middle, will no longer be able to eavesdrop, since the message is encrypted. The system is designed in such a way that only the intended recipients can 'decrypt' the message. This solution is one of the several applications of cryptography that you will learn on this site.

Cryptography thus includes a host of techniques to secure information, right from the ancient skytale to the modern cryptographic algorithms. It also comprises techniques to verify the authenticity of this information.

Glimpses from the past:

Back in the ancient times, cryptography found its place in anything, from luring the unsuspecting passers-by to utter a prayer for the dead in an attempt to read out the rather puzzling piece of text on the tombs, to penning 'auto-biographies' on stone. At times of war, it proved itself the elite force of goodwill, in some cases, shortening wars by years, thus saving human lives. If those were the times then, welcome to times now... The perfect blend of mathematical concepts and computation technology has culminated in a new dimension in cryptography. Today, we talk about DVD encryption, digital signatures to protect documents and even foiling your older sibling's elaborate scheme of reading your diary! - All thanks to cryptography.

Over the years, cryptography has thus come a really long way, from indecipherable scrawls on rocks to modern day encryption algorithms, standing the test of time.

(Cryptography is also our pet Egyptian macaw's name, btw!)

Fundamentals

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