Cryptography in which the order of letters is

Cryptography is a
science which has been used since early ages to hide secret messages. The early
know evidence of use of cryptography was found in the main chamber of the tomb
Khnumhotep II, where some unusual hieroglyphics were used instead of the ones
that are normally used. Another evidence of use of cryptography in early
civilizations can be found in the book called “Arthshashtra” written
by philosopher Kautilya, in which he mentioned giving spies assignments in secret
messages. In ancient days cryptography was mainly used to send classified
military strategies.

Classic cryptography
mainly uses transposition cipher, a technique in which the order of letters is
rearranged for example word ‘hello’ is written as ‘hlelo’ and substitution
ciphers, that systematically replace the letters with other letters. Ceasar
cipher is one of the early example of a substation cipher. The substitution
cipher used by Ceasar was shift by 3 where each letter is shifted by 3 places,
for example letter A is replaced with letter B and letter B is replaced with
letter E and follows, as shown in the figure below. The main drawback of
substitution ciper is the not the encryption key rather it is the secrecy of
the system, because once the system is understood the messages can be easily
decrypted.

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During 19th century the period when everything became electric,
an electro-mechanical contraption called as ‘Hebern rotor machine’ was
introduced by Hebern. This machine uses a rotor with the secret key can be
embedded in the rotation disc. The key embedded is used to encrypt the plain
text and provide the cipher text as output. After few years Arthur Scherbius a
German Engineer invented a machine called Engima machine which was heavily used
by German forces.

Cryptography was used only for military purposes until the
end of second world war. Commercial application of encryption started Post
world war II, when the business started trying to use cryptography to secure
data from other competitors. Realizing the demand IBM introduced and cipher
called Lucifer during 1970s, which was later called as Data Encryption
Standard(DES) and later NIST declared DES as a national standard block cipher.
The problem with the DES was that it used a short encryption key, and hence it
was broken in the year 1997. This lead to the development of Advanced Encryption Standard(AES), which was
later announced as a national standard by the NIST.

Modern Cryptography
is heavily dependent on binary mathematical calculations based on sophisticated
computer algorithms where secret keys are used to encrypt and decrypt the data.
There are 2 encryption algorithms that are currently in use, they are Symmetric
encryption and Asymmetric encryption. Symmetric encryption is the method in
which both the sender and receiver share the same key. Asymmetric encryption,
which is also known as public key cryptography, which uses 2 keys public and
private keys to encrypt and decrypt data. Public key can be shared with
everyone, but the private key is kept secret. Both private and public keys can
be used to encrypt a message but the key that’s not used in encryption can be
used to decrypt the message.

Now a day’s technology has made encryption a huge
necessity since major financial transactions are made online and internet has
become more accessible which forced the need for encryption in order in protect
personal data. In fact, we use cryptography in our day to day life without even
realizing it. We use a transfer protocol called HTTPS which enables SSL connection
between the two nodes of communication using Asymmetric key encryption. Even
the day to day messaging services like Facebook, whatsapp, etc were forced to
use cryptography in order to secure the zetta bytes of data being transfer
daily.