Breaking Panther

Panther is a sponge-based lightweight authenticated encryption scheme published at Indocrypt 2021. Its round function based on four Nonlinear Feedback Shift Registers (NFSRs). We show here that it possible to fully recover the secret key of construction by using single known plaintext-ciphertext pair and with minimal computational resources. Furthermore, we in ciphertext setting an attacker able knowledge decrypt all plaintext blocks expect for very first ones can forge tag only one call probability one. As demonstrate, problem design comes mainly from low number iterations during absorption phase. All our attacks have been implemented validated.