IntroductionCryptography is a field of science in which a sender encrypt information from outside world and then deliver through insecure medium. A person who work in secret intelligence, must share a his location with his friends so that they should complete their mission, or a person who know how to read ancient texts can protect information from some bad people.
The prefix "crypt" means "hidden" or "vault" and the suffix "graphy" stands for "writing."Every writing system have one common property and that is "encoded message property". According to this property if you don't know how to read it then you don't know about key.
For example I write a line another language and check whether this property satisfy my hypothesis.
علم انسا ن کا اک رشتہ ئے
This is a message which i need to understand. There are two possibilities to understand this message
1. I know about every word and where to read (language rules)
2. I have a reference which guide me.
"Knowledge and man have relation" , I can decipher it easily because this my native tongue.
However when old civilizations invade one another territory, Nations who win battle, abandon their civilization, destroy their engineering sites. Some of them also learn native.
First cipher had introduced by julius caesar, when cleopatra fallen in love with julius. Soldiers had search Cleopatra and julius everywhere. They introduce own method, so that they protect from soldiers and no one find them. More than 300 years their people understand what they say to each other.
Holy cipher named as "atbash" which had found in Holy book Bible (Hebrew).
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