Key committing security is a crucial metric of authentication encryption schemes, complementing the fundamental principles of confidentiality and integrity. It ensures that an adversary cannot decrypt a given ciphertext to different sets of key, nonce, and associated data. In this study, we explore a key committing attack on the authenticated encryption stream cipher Tiaoxin-346 from the perspective of internal state collisions. We establish a more rigorous constraint within the FROB framework by identifying a different settings of \(\left( k_{2}, Nonce, AD^{*}\right)\) for any specified \(\left( k_{1}, Nonce, AD_{1}\right)\) . Specifically, we demonstrate that for the Tiaoxin-346 algorithm, it is possible to find another settings of key \(k_{2}\) and associated data \(AD^{*}\) with a computational complexity of O(1), given any key \(k_{1}\) and \(AD_{1}\) . We provide a detailed explanation of the rationale and a step-by-step methodology for constructing an internal state collision at the seventh round of the update process, aimed at recovering the appropriate \(AD^{*}\) . Notably, the computational complexity of our attack is O(1), significantly lower than the generic attack complexity of \(O\left( 2^{64}\right)\) , which effectively violates the key commitment security of Tiaoxin-346. The results of this study contribute to refining the security of authenticated encryption algorithms and offer valuable insights for the design of round update functions in AES-based schemes.
