RC4 Encryption/Decryption
Encrypt or decrypt text using the RC4 (Rivest Cipher 4) algorithm. RC4 is a stream cipher that was widely used in protocols like SSL and WEP.
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Output
About RC4 Encryption
What is RC4?
RC4 (Rivest Cipher 4) is a stream cipher designed by Ron Rivest in 1987 for RSA Security. It generates a pseudorandom stream of bits that is combined with the plaintext using bitwise XOR for encryption. Unlike block ciphers that operate on fixed-sized blocks, RC4 encrypts one byte at a time.
For many years, RC4 was widely used in popular protocols and standards including SSL/TLS for secure web browsing, WEP for wireless network security, and various commercial applications due to its simplicity and speed.
How RC4 Works
RC4 operates in two stages:
- Key Scheduling Algorithm (KSA): Initializes a 256-byte state array using the provided key, creating a permutation of all possible byte values.
- Pseudo-Random Generation Algorithm (PRGA): Generates a keystream by continuously shuffling the state array and outputting bytes from it, which are then XORed with the plaintext.
This design allows RC4 to be very efficient in software implementations, as it requires only byte-level operations and minimal setup time compared to many block ciphers.
Key Features of Our RC4 Tool
- Support for variable key lengths (40 to 1024 bits)
- Multiple output format options (Base64 or Hexadecimal)
- Client-side encryption/decryption (your data never leaves your browser)
- Easy-to-use interface with random key generation
- Educational insights about the algorithm and its security limitations
Security Warning
RC4 is considered cryptographically broken and should not be used for secure applications. Several serious weaknesses have been discovered in the algorithm, making it vulnerable to various attacks. This tool is provided for educational purposes and legacy system compatibility only.
Historical Use Cases
Before its security weaknesses were widely known, RC4 was used in:
- SSL/TLS protocols for secure web browsing (until it was prohibited in 2015)
- WEP and WPA for wireless network security
- Microsoft Office document encryption (in older versions)
- PDF file encryption
- Various software applications needing simple encryption
Security Vulnerabilities
RC4 has several known vulnerabilities that led to its deprecation:
- Biased Outputs: The first few bytes of the keystream are biased, making them predictable
- Statistical Biases: RC4 outputs are not perfectly random, leading to distinguishing attacks
- Related Key Attacks: Weaknesses when similar keys are used
- WEP Weaknesses: The way RC4 was implemented in WEP was particularly vulnerable
Modern Alternatives
For secure applications, these modern alternatives are recommended instead of RC4:
- AES (Advanced Encryption Standard): The current standard for symmetric encryption
- ChaCha20: A modern stream cipher that offers better security and performance
- ChaCha20-Poly1305: Combines ChaCha20 with the Poly1305 authenticator for additional security