IDEA Encryption

IDEA (International Data Encryption Algorithm) is a symmetric-key block cipher designed to be secure and efficient.

Key Generation

Generate a secure key and initialization vector (IV) for IDEA encryption

Encrypt File

Upload a file and encrypt it with IDEA

Decrypt File

Upload an encrypted file and decrypt it with IDEA

About IDEA Encryption

IDEA (International Data Encryption Algorithm) is a symmetric-key block cipher designed by Xuejia Lai and James Massey in 1991 as a replacement for DES. It was used in Pretty Good Privacy (PGP) version 2.0 and became one of the most widely used encryption algorithms in the 1990s and early 2000s.

Key Features:
  • Block Size: 64 bits
  • Key Size: 128 bits
  • Rounds: 8.5 rounds
  • Structure: Substitution-permutation network (SPN)
  • Operations: Uses a mix of operations from different algebraic groups:
    • Addition modulo 2^16 (denoted by ⊞)
    • Multiplication modulo 2^16+1 (denoted by ⊙)
    • Bitwise exclusive OR (XOR, denoted by ⊕)
How IDEA Works:
  1. Key Schedule: The 128-bit key is expanded to generate 52 16-bit subkeys.
  2. Data Processing: The 64-bit input block is divided into four 16-bit sub-blocks.
  3. Round Function: Each round applies a complex series of operations:
    • Multiply first sub-block with first subkey
    • Add second sub-block and second subkey
    • Add third sub-block and third subkey
    • Multiply fourth sub-block with fourth subkey
    • XOR results of steps 1 and 3
    • XOR results of steps 2 and 4
    • Multiply result of step 5 with fifth subkey
    • Add results of steps 6 and 7
    • Multiply result of step 8 with sixth subkey
    • Add results of steps 7 and 9
    • XOR results of steps 1 and 9
    • XOR results of steps 3 and 9
    • XOR results of steps 2 and 10
    • XOR results of steps 4 and 10
  4. Output Transformation: After 8 rounds, a final half-round is applied.
Security and Applications:
  • Security: IDEA was considered very secure when introduced, but has been subject to various cryptanalytic attacks over time. The full 8.5-round IDEA is still considered secure against practical attacks, though it has been largely replaced by AES in modern applications.
  • Applications: IDEA was widely used in:
    • Pretty Good Privacy (PGP) email encryption
    • Various VPN implementations
    • Secure communications systems
  • Patent Status: IDEA was patented, but all patents have expired worldwide (as of 2012), making it free to use.
Variants:
  • MESH: A variant of IDEA with improved diffusion properties.
  • IDEA-NXT (also known as FOX): A family of block ciphers designed as successors to IDEA.
Note: While IDEA is still considered secure for many applications, modern systems typically prefer AES or other newer ciphers for new implementations due to their wider adoption, better performance on modern hardware, and larger block sizes.