RC4 Encrypt & Decrypt
Encrypt and decrypt text using the RC4 stream cipher algorithm with custom key input.
About RC4 Encryption
Our free online RC4 Encrypt & Decrypt tool allows you to encrypt and decrypt text using the RC4 (Rivest Cipher 4) stream cipher algorithm. RC4 is a simple and fast symmetric encryption algorithm that generates a pseudo-random stream of bits (keystream) based on a secret key.
RC4 was designed by Ron Rivest in 1987 and was widely used in protocols such as SSL/TLS and WEP. It supports variable key lengths from 1 to 256 bytes and operates as a stream cipher, meaning it encrypts data one byte at a time rather than in fixed-size blocks. The simplicity of RC4 makes it useful for educational purposes and lightweight applications.
This tool processes your data entirely in the browser using JavaScript and CryptoJS, ensuring your plaintext and keys never leave your device. Encrypt messages instantly or decrypt RC4-encrypted ciphertext with ease.
The auto-encrypt feature updates the encrypted output in real-time as you type, making it convenient for quick encryption. Simply enter your key and start typing to see the encrypted result.
Features
Stream Cipher
RC4 encrypts data one byte at a time for fast and efficient encryption.
Flexible Key Length
Support variable key lengths from 1 to 256 bytes.
Fast Processing
Encrypt and decrypt text instantly with minimal computational overhead.
Auto-Encrypt
Automatically encrypt as you type for real-time encryption results.
Privacy First
All processing happens in your browser. Your data never leaves your device.
One-Click Copy
Copy the encrypted or decrypted output to clipboard with a single click.
How to Use
Enter Your Key
Type or paste your encryption key into the key input field.
Enter Your Text
Type or paste the text you want to encrypt into the input editor.
Encrypt or Decrypt
Click Encrypt to encrypt your text or Decrypt to decrypt RC4-encrypted ciphertext.
Copy the Result
Click Copy to copy the encrypted or decrypted output to your clipboard.
Frequently Asked Questions
What is RC4?
RC4 (Rivest Cipher 4) is a symmetric stream cipher designed by Ron Rivest in 1987. It generates a pseudo-random keystream based on a secret key and XORs it with the plaintext to produce ciphertext. It supports variable key lengths from 1 to 256 bytes.
What is a stream cipher?
A stream cipher encrypts data one byte (or bit) at a time, as opposed to block ciphers that encrypt fixed-size blocks. Stream ciphers are generally faster and simpler to implement than block ciphers.
Is RC4 secure?
RC4 has known vulnerabilities and is no longer recommended for secure communications. It has been deprecated in TLS and is considered insecure for most modern applications. However, it is still useful for educational purposes and understanding stream cipher concepts.
What key length should I use?
RC4 supports key lengths from 1 to 256 bytes. For educational purposes, any length works. In practice, longer keys (e.g., 16 bytes or more) provide better security, although RC4 itself has fundamental weaknesses regardless of key length.
How does RC4 encryption work?
RC4 uses two algorithms: the Key Scheduling Algorithm (KSA) initializes a 256-byte state array based on the key, and the Pseudo-Random Generation Algorithm (PRGA) generates a keystream that is XORed with the plaintext to produce ciphertext. The same process decrypts ciphertext back to plaintext.
Is this RC4 tool free?
Yes, it is completely free to use with no registration, sign-up, or limits. All encryption and decryption happens in your browser using JavaScript, so your data stays private.