About RC4 Encryption
RC4 (Rivest Cipher 4) is a stream cipher designed by Ron Rivest in 1987 for RSA Security. It was
initially a trade secret, but was leaked in 1994 and has been widely analyzed since then.
- RC4 is a stream cipher, which means it encrypts individual bytes of data one at a time.
- It uses a variable key length, typically between 40 and 2048 bits.
- RC4 is notable for its simplicity and speed in software implementations.
- It was once widely used in protocols like WEP (Wireless Equivalent Privacy), SSL/TLS, and
various commercial products.
How RC4 Works:
- The algorithm uses a key to initialize a 256-byte state array.
- The state array is then used to generate a pseudo-random keystream.
- The keystream is XORed with the plaintext to produce the ciphertext.
- Decryption is performed by XORing the same keystream with the ciphertext.
Security Vulnerabilities:
RC4 is now considered cryptographically broken and should not be used in new systems for the
following reasons:
- Statistical biases in the keystream can lead to plaintext recovery in certain scenarios.
- The WEP protocol, which used RC4, was completely broken due to weaknesses in RC4 and its
implementation.
- In 2013, researchers demonstrated practical attacks against RC4 in TLS that could
recover user passwords and other sensitive information.
- In 2015, the "FREAK" attack exploited RC4 weaknesses in SSL/TLS implementations.
- Modern browsers and servers have disabled RC4 support due to these security concerns.
For secure communications, modern algorithms like AES, ChaCha20, or Twofish are strongly
recommended instead of RC4.