After the Kotov--Ushakov attack on the tropical implementation of Stickel protocol, various attempts have been made to create a secure variant of such implementation. Some of these attempts used a special class of commuting matrices resembling tropical circulants, and they have been proposed with claims of resilience against the Kotov--Ushakov attack, and even being potential post-quantum candidates. This paper, however, reveals that a form of the Kotov--Ushakov attack remains applicable and, moreover, there are heuristic implementations of that attack which have a polynomial time complexity and show an overwhelmingly good success rate.
public-key cryptography, key exchange protocol, cryptographic attack, tropical cryptography
94A60, 15A80