Let’s break down IDEA encryption, which stands for International Data Encryption Algorithm—a powerful cipher with a cool name and solid security chops.

🧠 What Is IDEA?

IDEA is a symmetric-key block cipher developed in 1991 by Xuejia Lai and James Massey. It was designed to replace older, less secure algorithms like DES and was used in early versions of Pretty Good Privacy (PGP).

⚙️ Key Features

• Block Size: Operates on 64-bit blocks of data.
• Key Length: Uses a 128-bit encryption key.
• Rounds: Goes through 8.5 rounds of processing (yup, that half-round is real—it’s part of the final transformation).
• Structure: Not a Feistel network—it uses a mix of operations to protect data:
  • Modular addition
  • Modular multiplication
  • Bitwise XOR

These three operations interact in a way that makes reverse-engineering the encrypted data extremely difficult.

🔄 How It Works (Simplified)

1. Key Expansion: The 128-bit key is split into 52 subkeys used across the rounds.
2. Rounds: Each round transforms the data using a unique combination of the three operations mentioned above.
3. Final Round (the 0.5): Applies a simplified version of the transformation to complete encryption.

🛡️ Strengths

• Strong resistance to differential and linear cryptanalysis.
• Efficient on both 32-bit and 64-bit systems.
• No known practical attacks when used properly with a good key.

⚠️ Weaknesses

• Limited block size (64 bits) makes it less suitable for encrypting large data volumes.
• Patented until 2012, which discouraged widespread adoption.
• Less common today—mostly replaced by newer standards like AES.