RC4 Encryption & Decryption
Apply the RC4 stream cipher. It is its own inverse, so one operation covers both directions — and its keystream bias is why TLS dropped it.
Input
Output (Base64)
Why this is still here
These ciphers are not offered as choices. They are offered because data encrypted with them exists — a column in a database nobody has migrated, a config file from 2009, a protocol capture — and reading it requires the same broken algorithm that wrote it.
DES has a 56-bit key, which the EFF brute-forced in under three days in 1998; a cloud instance does it in minutes today. Triple DES pushed that out by running DES three times, but its 64-bit block leaks structure after about 32 GB of data under one key — the Sweet32 attack — and NIST withdrew it in 2023. RC4’s keystream is measurably biased in its first bytes, which is what removed it from TLS.
Format compatibility
DES and Triple DES here use the OpenSSL passphrase convention: an 8-byte random salt, the key and IV derived with EVP_BytesToKey (MD5, one iteration), and the output framed as "Salted__" + salt + ciphertext, Base64-encoded.
That means a value produced by `openssl enc -des-cbc -a` decrypts here, and vice versa. It also means the key derivation is weak by modern standards — deliberately, because matching the format is the entire point.
Frequently asked questions
Can I use this to encrypt something today?
You can, and you should not. Anything you encrypt with DES or RC4 is protected only against someone who is not trying. The AES tool is one click away and is the right answer for new data.
Decryption fails with a padding error.
Almost always a wrong passphrase. It can also be the wrong mode (CBC vs ECB), or ciphertext produced by a tool that does not use the OpenSSL salt header.
Is my data sent anywhere?
No. These ciphers are implemented in the page and run entirely in your browser, which is exactly why it is safe to paste a legacy key here.