Universal Forgery and Key Recovery Attacks: Application to FKS, FKD and Keyak

In this paper, we provide a security analysis of the FullState Keyed Sponge (FKS), Full-State Keyed Duplex (FKD) and Keyak, one of the third-round CAESAR candidates, in the classic setting and the quantum model, respectively. In the classic setting, we present an universal forgery attack that can be implemented in O(2) queries, where c is the capacity. In the quantum model, by utilizing the Simon’s algorithm, we propose an efficient universal forgery attack to FKS, FKD and Keyak with complexity of O(c). Moreover, we also propose an efficient key recovery attack that can be implemented in O(c). Such attacks show that FKS, FKD and Keyak is completely broken in the quantum model.