Message authentication codes MACs are widely used in communication networks for authentication purposes. In EUROCRYPT 2002, Black and Rogaway proposed a parallelizable MAC PMAC, which is relatively efficient when a parallel environment is possible. This parallelism is achieved via constant multiplications in the underlying finite field. In order to yield a better solution, Rogaway refined PMAC in ASIACRYPT 2004 by using a powering-up construction to generate the constants. This is in contrast to the first design that uses successive words of the gray code to generate the constants. In this paper, we analyze how some unique characteristics of these constants result in weaknesses of the respective PMAC designs against forgery attacks in different ways. Thus, our analysis highlights some pitfalls that designers should be mindful of when designing schemes that exploit such constants. Copyright
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This research was not carried out under any specific funding.