🔐 Custom Shift-Based Encoder/Decoder

A Java-based text obfuscation tool that implements a shift cipher using a custom reference table containing letters, numbers, and special symbols. Inspired by classical Caesar and Vigenère ciphers, this encoder allows dynamic shifting based on a selected offset character, creating an effective and customizable encoding/decoding scheme.

📌 Features

• Encode plaintext into an obfuscated string using a character-based offset
• Decode encoded messages back to original plaintext
• Custom reference table including A-Z, 0-9, and symbols ()*+,-./
• Preserves characters not found in the reference table
• Object-Oriented Design with clearly structured encode() and decode() methods
• Easily extensible and testable

🧠 Logic Overview

1. The first character of the encoded string is the offset character.
2. All valid characters (from the reference table) are shifted based on the offset.
3. Characters not found in the table are left unchanged.
4. Decoding uses the offset to reverse the shift and retrieve the original message.

🔄 Example

For offset 'B' (1-shift):
Plaintext : HELLO WORLD
Encoded : BGDKKN VNQKC

For offset 'F' (5-shift):
Plaintext : HELLO WORLD
Encoded : FC/GGJ RJMG.

🧱 Reference Table and Shift Variants

Index	Original	Shift #1 (B)	Shift #2 (F)
0	A	B	F
1	B	A	E
2	C	B	D
3	D	C	C
4	E	D	B
5	F	E	A
6	G	F	B
7	H	G	C
8	I	H	D
9	J	I	E
10	K	J	F
11	L	K	G
12	M	L	H
13	N	M	I
14	O	N	J
15	P	O	K
16	Q	P	L
17	R	Q	M
18	S	R	N
19	T	S	O
20	U	T	P
21	V	U	Q
22	W	V	R
23	X	W	S
24	Y	X	T
25	Z	Y	U
26	0	Z	V
27	1	0	W
28	2	1	X
29	3	2	Y
30	4	3	Z
31	5	4	0
32	6	5	1
33	7	6	2
34	8	7	3
35	9	8	4
36	(	9	5
37	)	(	6
38	*	)	7
39	+	*	8
40	,	+	9
41	-	,	(
42	.	-	)
43	/	.	*

🛠️ Installation & Running

Prerequisites

• Java 8 or higher
• Git (optional, for cloning)

Steps

# Clone the repository
git clone https://github.com/VishalJeyaram/encoder.git
cd encoder

# Compile and run
javac Encoder.java
java Encoder