CipherSaber-2 cipher
Encrypt or decrypt text with CipherSaber-2 — RC4 with a random 10-byte IV and repeated key setup (rounds). Text or encoded keys, hex or base64. Runs in your browser; nothing is uploaded.
About this tool
CipherSaber-2 encrypts and decrypts text with the CipherSaber cipher — a deliberately minimalist symmetric cipher built on RC4 (ARCFOUR). You supply the key, optionally the rounds and encoding, and the tool handles the random initialization vector for you — handy for interoperating with CipherSaber implementations, solving CTFs, or learning how stream ciphers work.
- Symmetric: CipherSaber XORs your data with a key-derived keystream, so the same operation conceptually encrypts and decrypts. To recover a message, use the same key, rounds and encoding it was encrypted with.
- Random IV: every encryption generates a fresh, random 10-byte initialization vector (IV) and prepends it to the ciphertext in the clear. The decryptor reads the IV back automatically — you only need the key. You can optionally supply an explicit IV (encoded, 10 bytes) for deterministic output.
- Rounds (CipherSaber-2): the 2 variant repeats RC4's key-scheduling loop
several times — the spec recommends 20 — to better diffuse the key and
resist the FMS key-recovery attack that breaks CipherSaber-1.
roundsmust match on both encrypt and decrypt. (Setrounds = 1for original CipherSaber-1.) - Key: enter it as a text passphrase, or as an encoded (hex / base64) byte string. The key plus the 10-byte IV must total at most 256 bytes.
- Encoding: the ciphertext (and an encoded key/IV) are hex or base64; the plaintext is always UTF-8 text.
Security warning
RC4 — and therefore CipherSaber — is cryptographically broken; practical attacks recover plaintext, and RC4 is banned from TLS. CipherSaber was designed as an easy-to-memorize teaching cipher, not to protect real secrets. Use this tool for interop, CTFs and education only. For real encryption use the aes-cipher, text-encrypt or encrypt-file tools instead.
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
Why is the ciphertext different every time I encrypt the same message?
Each encryption draws a fresh random 10-byte IV and prepends it to the output, so two runs never match — that's correct CipherSaber behavior. If you need reproducible output (e.g. for a test vector), supply an explicit 10-byte IV in the IV field, encoded in the selected hex/base64 format.
What rounds value do I need, and what about CipherSaber-1?
The CipherSaber-2 spec recommends 20 (the default). The value must be identical on encrypt and decrypt — a mismatch produces garbage. Set rounds = 1 to interoperate with original CipherSaber-1 messages.
Decryption failed with "not valid UTF-8" or "ciphertext too short" — why?
"Ciphertext too short" means the decoded input has fewer than 10 bytes, so there's no room for the IV — usually a truncated paste or the wrong encoding selected. "Not valid UTF-8" means RC4 ran but produced bytes that aren't text: almost always a wrong key, wrong rounds, or a hex/base64 mismatch.
Is there a limit on the key size?
Yes — RC4's key schedule caps the session key at 256 bytes, and the 10-byte IV is part of it, so your key (passphrase bytes, or decoded bytes in encoded mode) can be at most 246 bytes. An empty key is rejected.
Developer & Automation Access
Run it from the terminal
Same engine as this page, headless — via the gizza CLI:
gizza tool ciphersaber2 "Text to encrypt…" 'key=passphrase, or encoded 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/ciphersaber2/?data=Text%20to%20encrypt%E2%80%A6&operation=encrypt&key=passphrase%2C%20or%20encoded%20key&key_format=text&rounds=20&iv=blank%20%3D%20random%20IV&format=hexMachine-readable descriptor: tool.json — title + parameters JSON Schema for agents.