In my experience, implementing the Blowfish Cipher in Python was a challenging yet rewarding task. I utilized the PyCryptoDome library which provides cryptographic recipes and primitives. The key setup phase involved generating subkeys from a variable-length key, up to 448 bits. This process required careful attention as it is crucial for security.
The encryption phase consisted of dividing input into blocks and applying complex operations such as XOR, addition, and lookup in S-boxes. These operations were repeated 16 times per block (Feistel network). Debugging this part was particularly demanding due to its iterative nature and dependence on previous results.
Decryption was essentially the reverse process of encryption, with subkeys applied in reverse order. Ensuring correct implementation of decryption was critical to validate the entire cipher’s functionality.
Overall, while the complexity of Blowfish presented some difficulties, successfully implementing it provided valuable insights into symmetric-key cryptography and reinforced my understanding of Python programming.
