Rust "EAC Authentication Timeout": how to fix it

Start Rust only from your Steam library. Facepunch says other launch methods mean EAC doesn't start, which causes errors like this one.

Close Rust and wait up to 10 minutes. Facepunch says this lets EAC refresh its cache, which may resolve the problem.

Verify your game files: in Steam, right-click Rust, choose Properties, open Local Files and click "Verify integrity of game files".

Repair EAC: right-click Rust in Steam, choose Manage, then Browse local files, and open the EasyAntiCheat folder. Click the Explorer address bar, type EasyAntiCheat_EOS_Setup.exe repair and press Enter, then allow the administrator prompt. Facepunch notes a small console window flashes briefly and there is no visible interface, but the repair still runs.

Restart your PC, and turn your router or modem off and on again.

Install any pending Windows updates.

Update your antivirus, and see whether temporarily disabling it changes anything, as Facepunch's article suggests.

Delete RustClient.exe.eac from the EasyAntiCheat folder inside your Rust install (...\Steam\steamapps\common\Rust\EasyAntiCheat) if it exists.

Open output_log.txt in your Rust folder and check near the bottom for programs EAC marked as "forbidden"; close any it names from Task Manager.

If nothing above works, do a fresh install: delete the whole Rust folder, then reinstall from Steam. Facepunch's article lists this as the last resort.

If it began for you on every server at the same time other players started posting the same error, check /rust/ and the latest devblog for an outage note before spending time on the reinstall.