RC4: Design, Weaknesses & WEP Attacks

RC4 was the most widely used stream cipher for 20 years — used in WEP, TLS, and SSL. Today it is completely broken. Understanding its failure teaches critical lessons about cryptographic design.

RC4 (Rivest Cipher 4) was designed by Ron Rivest in 1987 for RSA Security. It was kept as a trade secret until 1994 when it was reverse-engineered and published anonymously as 'Alleged RC4' (ARC4).