Pure TEA (Tiny Encryption Algorithm) Implementation in Python

This repository contains a clean, educational implementation of the TEA (Tiny Encryption Algorithm) in Python, written entirely without using structured data libraries (such as Python's built-in struct module). All byte manipulation, padding, and conversion into 32-bit registers are performed manually using low-level bitwise operations.

📌 Features

• No Structural Dependencies: Designed completely from scratch using fundamental data types, bitwise shifts, and masks.
• 32-bit Integer Simulation: Python handles arbitrarily large integers automatically. To perfectly match C's uint32_t modulo overflow behavior required by TEA, an & 0xFFFFFFFF mask is applied to every mathematical operation.
• Manual Byte Parsing: Blocks of data and keys are parsed from bytes into arithmetic variables (left, right, k0–k3) using explicit bit shifts (<< 24, << 16, etc.).
• Feistel Cipher Structure: Implements standard 32 cycles (64 rounds) of the Feistel network.
• Zero Padding: Automatically pads input text with null bytes (\x00) to guarantee compatibility with 8-byte block sizes.

🚀 Getting Started

No third-party libraries are required. The script runs natively on any modern Python 3 installation.

Test Enter your message and encryption key when prompted:

Enter text for TEA encryption: Hello World!
Enter TEA encryption key: my_secret_key

Encrypted bytes: b'\x84\xec\xa9...\x1f'
Decrypted text: Hello World!

⚠️ Security Disclaimer

The original Tiny Encryption Algorithm (TEA) is vulnerable to related-key attacks, where each 128-bit key corresponds to three other equivalent keys. This effectively reduces its keyspace to 126 bits. It is also susceptible to differential cryptanalysis.

This repository is intended strictly for educational and academic purposes to demonstrate the mechanics of symmetric block ciphers. It should not be deployed in production environments handling sensitive data.