[Pierre-Marie Baty]

I assume you're talking about Steam authentication, not WON authentication (i.e, you're usin Steam and not the old version of HL)

You know this is considered piracy ? We don't support piracy here, so we won't tell you how to get a new CD key illegally. What we can tell you, though, is that with the current release of Steam you *NEED* to have an internet connection available to play, even on LAN. This sucks, but there's no other {legal} way to play on LAN with Steam.