F8 dan F5 are standarlized by 3GPP to provide confidentiality and integrity, respectively. It was claimed that F8 and F9 are secure it the underlying block cipher is a Pseudo Random Permutation (PRP), where F9 is a alightly modified version of F9. In this paper, however, we disprove both claims by showing a countexexample. We fist construct a PRP F with the following property . There isa constant cst such that for any key K, Fk(,)=FK (.) We then show that F8 and F9 are comepletely insecure if F is used as the underlying imply the security of F8 and F9 and it is imposible to prove their security under PRP assumption It should be attessed hat these results do not implly the original F8 dan F9 (with KASUMI as the underflying block chipher) are insure, or broken They simply undermini their provable security