Blowfish Encryption/Decryption Tool

Blowfish is a symmetric-key block cipher designed by Bruce Schneier in 1993. It was one of the first secure block ciphers not subject to patents and is freely available for anyone to use.

Blowfish uses a 64-bit block size and supports variable key lengths from 32 bits to 448 bits. It uses a 16-round Feistel network structure, making it both fast and secure for most applications.

Key Features

• Variable key length: 32 to 448 bits (4 to 56 bytes), offering flexibility in security levels
• 64-bit block size: Processes data in 8-byte blocks
• 16-round Feistel network: Provides strong diffusion and confusion
• Fast encryption: Optimized for 32-bit processors, significantly faster than DES

Encryption Modes

• CBC: Each plaintext block is XORed with the previous ciphertext block before encryption. Requires IV, most secure.
• ECB: Each block encrypted independently. No IV needed, but same plaintext produces same ciphertext.
• CFB: Converts block cipher to stream cipher. Requires IV.
• OFB: Output feedback mode, converts block cipher to stream cipher. Requires IV.

Security Considerations

• Blowfish's 64-bit block size makes it vulnerable to birthday attacks when encrypting large amounts of data (>32GB) with the same key.
• For new projects requiring maximum security, consider using AES or Blowfish's successor, Twofish.
• Always use CBC or other chaining modes instead of ECB for better security.
• Use a unique IV for each encryption operation with the same key.

Use Cases

• Password hashing: bcrypt is based on Blowfish and is widely used for password storage
• File encryption: Suitable for encrypting individual files and archives
• VPN and secure communications: Used in OpenVPN and other security protocols
• Legacy system compatibility: Maintaining compatibility with systems using Blowfish

References

• Bruce Schneier's Official Blowfish Page
• Wikipedia - Blowfish (cipher)