A waitress in a café gave me a key for the local wireless network. It read 1123456789. As I was entering it in my iPad she seemed to be genuinely impressed by the device. Then came the embarrassing moment: I wasn’t able to join the network, while she was connected just fine with her notebook, as she informed me.

It turns out, that the digit-only key was probably a hexadecimal code of a 40-bit WEP passphrase. Full-fledged computers running recent versions Mac OS X or Windows automatically recognize hexadecimal (as opposed to ASCII or plain-text) Wi-Fi keys and interpret them correctly, iPad does not. Next time I’ll try prefixing it with ‘$’ or ‘0x’. So watch out for Wi-Fi keys that consists of 10 or 26 digits 0-9 and letters A to F. I’d expect this to apply to iPhone and iPod touch as well.

Update 10 June: Prefixing with ‘$’ or ‘0x’ did not help. It looks like the iPad does not support 40-bit WEP passphrase (at least not entered in hex). Sure, it’s an obsolete technology, but if Apple wants to drop it, they should do it explicitly instead of just displaying an “Unable to join network” message.