🔐 Simplified AES-128 Implementation in Java

📌 Author

Shaina

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🧠 What is AES?

The Advanced Encryption Standard (AES) is a symmetric block cipher used worldwide for secure data encryption. It operates on 128-bit blocks with key sizes of 128, 192, or 256 bits.

AES Core Operations:

• SubBytes – Byte substitution using an S-Box
• ShiftRows – Cyclically shift rows in the state
• MixColumns – Mix data within each column using matrix multiplication
• AddRoundKey – XOR the state with a round-specific key

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🎯 Objective

This project demonstrates a simplified AES-128 encryption/decryption algorithm in Java, using:

• A reduced S-Box (16 entries for learning simplicity)
• Basic MixColumns and Galois Field logic
• Full key expansion for 10 rounds

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🛠️ Features

• 128-bit block and key size
• 10 Rounds of encryption and decryption
• Custom simplified:
  • S-Box / Inverse S-Box
  • MixColumns logic
• Includes both encryption and decryption flows
• Console output with verification

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🧪 Encryption/Decryption Procedure

Encryption

1. Key Expansion
2. Initial AddRoundKey
3. Rounds 1-9
   • SubBytes → ShiftRows → MixColumns → AddRoundKey
4. Final Round (10)
   • SubBytes → ShiftRows → AddRoundKey

Decryption

1. Initial AddRoundKey
2. Rounds 9-1
   • InvShiftRows → InvSubBytes → AddRoundKey → InvMixColumns
3. Final Round
   • InvShiftRows → InvSubBytes → AddRoundKey

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▶️ How to Compile & Run

javac SimplifiedAES128.java
java SimplifiedAES128

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🍴 How to Fork This Repository

Want to use or contribute to this project? Follow the steps below to fork and work with your own copy.

🔗 Repository URL

https://github.com/shaina-gh/AES

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🔄 Step-by-Step Instructions

1. Login to GitHub and go to the repo: shaina-gh/AES
2. Click the "Fork" button at the top-right corner.
3. GitHub will create a copy under your own account.

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🧪 After Forking – Get Started Locally

# 1. Clone your forked repository
git clone https://github.com/YOUR-USERNAME/AES.git

# 2. Navigate into the project directory
cd AES

# 3. Compile and run the project
javac SimplifiedAES128.java
java SimplifiedAES128