Asymmetric Cryptography with a Hidden Monomial

In [1]T. Matsumoto and H. Imai have presented a very efficient, "candidate" algorithm, called C*, for asymmetric cryptography. This algorithm was broken in [2]. Then in [3], I have suggested two algorithms, HFE and IP, to repair C*. However the secret key computations of HFE and IP are not as efficient as in the original algorithm C*. IS it possible to repair C* with the same kind of very easy secret key computations? This question is the subject of this paper. Unfortunately, we will see that for all the "easy" transformations of C* the answer is no. However one of the new ideas of this paper will enable us to suggest a candidate algorithm for assymetric signatures of length only 64 bits. An extended version of this paper can be obtained from the author.