What is cryptography

The term cryptography is derived from Greek, kryptos means “hidden” or “secret” and graphy means “writing”. So, cryptography is the practice and study of creating a secret information. Cryptography works by Cryptography is a part of mathematics and computer science.

Cryptography is used in applications present in technologically advanced societies; examples include the security of ATM cards, computer passwords, and electronic commerce, which all depend on cryptography. In short we can say that cryptography is needed to secure a secret document. A person who is master in cryptography is called cryptographer

How cryptography works

For example someone has a secret document to secure. Any document can be secured using cryptography. For example we have to secure the word “Read” using cryptography. The word “Read” in cryptography is called Plain text. Using a set of rule called algorithm, the plain text is changed into cipher text. This process is called encryption. The result of this encryption process is the word “Uhdg”. This is the cipher text.

A set of rule (algorithm) that is used in encryption can be different. There are many algorithm used in encryption. At the above example we use Caesar Cipher algorithm that is used by Julius Caesar to secure his document

The reverse process of encryption is called decryption. The input is a cipher text. And the result of decryption process is plain text.

History of cryptography

Cryptography is already used since ancient era. Julius Caesar used cryptography to secure his message from his enemy. He replaced a character with its next three character. For example a character ‘A’ in alphabet will be replaced by character ‘D’. And so on. See the list below of Julius Caesar algorithm.

Plain text : a b c d e f g h I j k l m n o p q r s t u v w x y z
Cipher Text : d e f g h I j k l m n o p q r s t u v w x y z a b c

In the era of World War II, German Nazi was also used cryptography to secure its message. Nazi used a machine called Enigma to encrypt and decrypt the messages. In this way Nazi thought its message would be difficult to break by US and its allies. Below is a picture of Enigma used by Nazi.

Unfortunately the algorithm of Enigma can be broken by US army.
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