In early times, keeping data secret was not hard. Many years ago, when some people were educated, the use of written language only often satisfied to hold data from becoming common knowledge. To hold secrets then, you only had to write them down, keep them protected from those few people who could read, and stop others from learning how to read. Knowing the meaning of a document is difficult if it is written in a language you do not know.
History shows us that important secrets were stored by writing them down and hiding them from educated people. Persian border guards in the fourth-century b.c. allow blank wax writing sheets pass, but the sheets covered a message warning Greece of a coming attack.
The message was fully covered by a thin layer of fresh wax. Writers also draw messages on the shaved heads of messengers. When their hair got back in, the messengers could travel hidden through opponent fields. When they reached their destination, their heads were cut and the knowledge was shown. But the fate of nations could not depend for very long on such method, which depended completely on these methods to keep the writing secret. It did not take very long for ancient military leaders to produce and use more sophisticated methods. Since then, encryption has been a way of using more complex tactics to stay one move ahead of those who want your confidential data.
From what we understand of early civilizations, they liked a good puzzle. What greater puzzle than to cover a message using a sequence of steps? Unless you knew the steps used, the algorithm used to produce the cipher, you couldn’t decipher it without a great deal of difficulty.