Get them before they get you.

This has been the operating premise in use ever since means of communication other than person to person conversation were devised. What started out as mere letter substitutions in documents has evolved into a fully fledged discipline in itself. Almost every government in the world devotes money by the truckloads annually in an effort to make their communications secure and break into everyone else’s.

At its most fundamental level, cryptography involves the act of successfully conveying a message to an intended receiver without being intercepted by eavesdroppers. The original message, known as the plaintext, is transformed to ‘ciphertext’ using a suitable key and is sent to the intended recipient through an insecure means of communication . This is then converted back to the plaintext by the receiver using a key (that is not necessarily the same as the first key).

 

The question then arises as to how the ciphertext is generated using a key.  For this purpose, there exists a myriad of algorithms with great variation in sophistication, expediency and reliability – From primitive XOR functions that would keep out none but the most oblivious to the Advanced Encryption Standard (AES) which has withstood the test of time with over two decades of rigorous scrutiny. Despite the immense advances, no single algorithm can claim to be completely secure.  This is owing to the fact that, regardless of the ingenuity of the algorithm, there will always be patterns that the discernible cryptanalyst can potentially detect.

Among the more common misconceptions among novices is that the security of a cryptosystem lies in its algorithm. This cannot be farther from the truth as assuming a lack of information on the part of the attacker can be fatally dangerous. This, in fact, falls under a category of tactics called ‘obscurity’ which thrives on denying specifics to outsiders and pining hopes on them not being uncovered by other techniques. One of the starting assumptions, therefore, is that all particulars of an algorithm is known to all potential attackers and hence the security lies entirely in the key and how well it is guarded.

The question then arises, if this is the case, then why bother finding better algorithms? The straightforward answer is to eliminate all forms of attack other than ‘Brute Force’ which is simply the usage of all possible keys that the algorithm can accept until an intelligible text is obtained. A good algorithm, therefore, is one which an attacker cannot crack despite having at his disposal all information regarding the intricacies of its inner workings.

While at first glance, it may seem to be a topic confined to the realms of military intelligence and espionage, cryptography commands relevance in almost all walks of life. Some of the more well known applications include Authentication of Identity, Credentialing Systems and Digital Signatures. Indeed, very nearly every electronic transmission makes use of cryptography.

Here is an application of cryptography that the more fortunate amongst us can potentially make use of in real life. ;)

ARJUN MATHEW ERANACAL