Pour gagner du temps, la réponse à la question se trouve sur le site de Steamworks:
https://partner.steamgames.com/documentation/api
Il est bien clair que Steam utilise son propre système de DRM. Ce système s'appelle VAC et fonctionne "comme un anti-virus" !
DRM
Steamworks Digital Rights Management wraps your game's compiled executable and checks to make sure that it is running under an authenticated instance of Steam. This DRM solution is the same as the one used to protect games like Half-Life 2 and Counter-Strike: Source. Steamworks DRM has been heavily road-tested and is customer-friendly.
In addition to DRM solutions, Steamworks also offers protection for game through day one release by shipping encrypted media to stores worldwide. There's no worry that your game will leak early from the manufacturing path, because your game stays encrypted until the moment you decide to release it. This protection can be added to your game simply by handing us finished bits or a gold master.
Valve Anti-Cheat (VAC)
see multiplayer auth headers: steam_gameserver.h, ISteamGameServer.h, ISteamUser.h
Integration work with the VAC Steamworks C++ API is simple, because the heavy-lifting is left to Steam. An advantage is that cheat detection is not handled directly by your game client. The only thing your game needs to do is use the API to find out whether or not a given user is VAC banned.
VAC is a component of Steamworks and the Steam client, and works by scanning the users system for cheats while your game is running. It works a lot like a virus scanner, and has a database of known cheats to detect.
