(What is the RC4 encryption key size when utilizing WPA with Temporal Key Integrity Protocol...

WPA with TKIP was designed as an interim improvement over WEP while still using the RC4 stream cipher for compatibility with legacy hardware. TKIP addresses WEP’s major weaknesses by introducing per-packet key mixing, a message integrity mechanism (“Michael”), and replay protection. In TKIP, the encryption key used with RC4 is 128 bits. Practically, TKIP derives a per-packet RC4 key from a 128-bit temporal key (TK), the transmitter’s MAC address, and a sequence counter (TKIP Sequence Counter, TSC) to avoid the simple IV reuse patterns that made WEP easy to break. Even with these improvements, TKIP has known weaknesses and is deprecated in favor of WPA2/WPA3 using AES-based CCMP/GCMP. But strictly for the question asked, TKIP’s RC4 keying material is based on a 128-bit key size, not 40/56-bit legacy sizes and not 256-bit.