Why does cellular communication protocols use A5 or KASUMI and not AES or 3DES or RSA?
I have read that A5 is not that secure, is this the case?
Are A5 or KASUMI used anywhere else? Why only in cellular?
It seems to me this is for historical and technical reasons. A5/1 and A5/2 seem to be rather old designs from late 1980s. They do not appear to be in use any more. There was no AES at that time and 3DES is block cipher and GSM networks vendors apparently wanted stream ciphers back then. KASUMI seems to have been accepted also around the the time or before AES was announced, so they couldn't have made AES the standard cipher either. Also, AES is USA standard while these GSM network standards are international, and politics is a thing.