Blowfish cipher
Encrypt or decrypt data with Blowfish (ECB/CBC), hex or base64, with a variable 4–56 byte key. Runs in your browser; nothing is uploaded.
About this tool
Blowfish cipher encrypts or decrypts data with Blowfish in ECB or CBC mode, with hex or base64 key/IV/ciphertext. Blowfish takes a variable-length key from 4 to 56 bytes (32–448 bits) and operates on 64-bit (8-byte) blocks.
⚠️ Blowfish is a legacy cipher. Its 64-bit block size makes it vulnerable to birthday/Sweet32 attacks when encrypting large amounts of data with one key. Use this tool only to decrypt legacy data or for interop with old systems — for new encryption use AES (the
aes-ciphertool) or a passphrase tool.
- Key: 4–56 bytes. IV: 8 bytes (CBC only).
- CBC uses PKCS#7 padding; ECB too (and reveals patterns — avoid).
Privacy
Everything runs in your browser via WebAssembly — your key and data never leave the device. Also available from the gizza CLI and in chat.
FAQ
What key lengths does Blowfish accept?
Anything from 4 to 56 bytes (32–448 bits). The key must be supplied in the selected data format — base64 by default, or hex — and the tool rejects keys outside that range with an explicit length error. Note that the key length is measured after decoding, so a 16-character hex string is an 8-byte key.
Do I need an IV, and how long must it be?
Only in CBC mode, where the IV must be exactly 8 bytes (Blowfish's block size) encoded in the same format as the key. In ECB mode there is no IV — leave the field empty. If CBC decryption produces garbage, the usual culprit is a wrong or reused IV.
Why does decryption fail with a padding error?
Both modes use PKCS#7 padding, so the last block must unpad cleanly. A padding failure almost always means the key, mode (CBC vs ECB), or data format (base64 vs hex) doesn't match what was used to encrypt — not that the ciphertext is "corrupt".
Is Blowfish still safe to use for new data?
No — its 64-bit block size makes it vulnerable to Sweet32-style birthday attacks once you encrypt enough data under one key. Use it to decrypt legacy data or interoperate with old systems, and pick AES (see the aes-cipher tool) for anything new.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool blowfish-cipher "Text to encrypt…" 'key=base64 or hex key'New to the CLI? Get gizza →
Open it by URL
Pre-fill and auto-run this tool with query parameters — the names match the API/CLI:
https://gizza.ai/tools/blowfish-cipher/?data=Text%20to%20encrypt%E2%80%A6&operation=encrypt&cipher=cbc&key=base64%20or%20hex%20key&iv=base64%20or%20hex%20iv&format=base64Machine-readable descriptor: tool.json — title + parameters JSON Schema for agents.