Download this: http://www.lan.kth.se/eduroam/AddTrust_External_CA_Root.pem

Edit wpa_supplicant.conf:

network={
ssid=”eduroam”
key_mgmt=WPA-EAP IEEE8021X
eap=TTLS
identity=”username@kth.se”
anonymous_identity=”username@kth.se”
password=”password”
ca_cert=”/usr/local/share/certs/eduroam.pem”
phase2=”auth=PAP”
}