What was the first cipher?

Answer:

The first cipher was made by Julius Caesar who used it to communicate with his generals.
It is named 'Caesar Box' after the creater.

The system goes as follows:
First selct a message to be encrypted. Make sure the length of the characters your message is a perfect square.
For example: "CAESAR BOX"
Write it in a square grid (here, 3*3 grid)
C A E
S A R
B O X

Now read it horizontally....
The encrypted message shall be CSBAAOERX

Ensei's background, although correct, is a bit shady.

When making this cipher, the length of it should be a perfect square.

eg. 4; 9; 16; 25; etc.

Now this is how it works. Suppose we use 9 as the length.

N B H O A U T D H

Since 9 is the lenth, we should make 3 rows of horizontal letters, as follows:

N B H

O A U

T D H

Now read it vertically, it should read, NOT BAD HUH.