README

This module written by javascript is divided into three parts, encoding, decoding and selftesting(mocha).

Usage Flow

Step 1.

First, User make the program execute, and program will print "(1)Encoding Mode", "(2)Decoding Mode", and "(3)Run Sample" on the screen to help user to select the options.

Info: character encoding should be utf8.

Step 2.

In Encoding Mode, the program will print "Please type letters, words, or sentences".

Step 2.1

Randonly choose (chosen by rand()) a number as a offset and it is less than 26. Shift english alphabet [offset] digits.

Example

Clear Code:  ABCD...WXYZ
Secret Code: WXYZ...STUV
**** // if the offset is 4, stars will be 4.

Step 2.2

if you finish Step 2.1, clear code and secret code like Step 2.1 example will be printed on scrren and output (don't append) to a file named cesa.txt without clear code.

Step 3.

In decoding Mode, the program will read cesa.txt to get the secret code and stars and shift secret code the number of stars to rebuild clear code.

Step 3.1

Print the clear code on screen but don't output it to cesa.txt