The problem is that GSM does not provide integrity - hence this defcon example of building a fake basestation which the UE can camp on. I'm unaware of the gsm sect regarding display of ciphering status, I don't think there is a straight forward way of reading whether UE has ciphering active/is in confidential mode on the N900. The only possible way is to read FTDs but the celluar component would have to built with R+D mode on and thats definately not the case at the moment..