A Forgery Attack on the Candidate LTE Integrity Algorithm 128-EIA3

In this note we show that the message authentication code 128-EIA3 considered for adoption as one of the integrity algorithms of the emerging mobile standard LTE is vulnerable to a simple existential forgery attack. This attack allows, given any message and the associated MAC value under an unknown integrity key and an initial vector, to predict the MAC value of a related message under the same key and the same initial vector with a success probability 1/2