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Fundamentals of Network Security: Understanding Encryption and Decryption

written by: Ashwin Satyanarayana•edited by: Ronda Bowen•updated: 7/4/2011

Did you ever send a secret message to someone? Maybe you never felt the need to, but in most cases - all the way from ancient days of Greece to the present and beyond - encryption has always been around. So how does it work? What does it do? Why is encryption mentioned so important?

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    Encrypting and Decrypting Messages

    Julius Ceaser, who happens to be one of the first ever to use encryption, has a rather unique way of sending messages to others. Modern encryption is ubiquitous in the security arena. Encryption, Decryption and Cryptography are terms you would have heard of or read about each time you read about Security now-a-days.

    Cryptography is nothing but secretive, hidden and clandestine writing what is written in a way that only the recipient who knows how to crack it can decipher it. Modern day encryption is used for more or less the same reasons as the ancient days -- to protect the contents of the information from being known to people who aren’t supposed to know. Enigma (the machine that was used during the World War 2), for instance, is famous for sending encrypted messages. The reason why encryption takes such epic importance is due to the fact that information is now shared virtually on the Internet.

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    How Encryption Works

    net-security.org has a beautiful way to explain how encryption works and I couldn’t help but adapt that explanation here.

    This is we encrypt a simple message like “Send Me Link Love"

    Take a string of alphabets as shown below

    ABCDEFGHIJKLMNOPQRSTUVWXYZ

    Have another string of alphabets like those shown below

    ABCDEFGHIJKLMNOPQRSTUVWXYZ

    Reposition the alphabets such that we move each alphabet in this string to 4 places to the right. So that it looks like this:

    WXYZABCDEFGHIJKLMNOPQRSTUV

    Now if you keep both the strings one below the other, like this

    ABCD EFGH IJKL MNOP QRST UVWXYZ

    WXYZ ABCD EFGH IJKL MNOP QRSTUV

    You have one re-arranged alphabet that corresponds to the original alphabet you would like to use. Hence, “Send Me Link Love" would read as “OAJZ IA HEJG HKRA"

    So you could now successfully encrypt a message, using an algorithm (Moving it to X places right and writing down the alphabet that corresponds to the original one , after moving it) and a key ( that you moved it to 4 places right).

    So if your recipient knows this, it is easy to decrypt the code and read the message. However, from a purely security standpoint -- this is still very vulnerable to hacks because it is relatively easy to try the keys between the range of 0 to 26 in this case and crack the code, isn’t it?

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    Importance of Strength and Complexity

    Until computers came about, it was too difficult to make encryption any more complex than humanly possible. However, the advent of computers saw miracles happening. We have complexity in encryption technologies that is, well, mind-boggling. But equally appalling news is that there are just as powerful software to decrypt these encrypted information packets. DES (Data Encryption Standard) has been in use for a long time now for standard encryption use which is now proving to be a little outdated which mandated newer and much more robust protocols like Triple DES (3DES), an extended algorithm that uses one, two, or three keys and three calculation steps; RSA Security's secret-key ciphers for RC2 and RC4 etc.