The GH Public-Key Cryptosystem

This paper will propose an efficient algorithm that utilizes the signed-digit representation to compute the kth term of a characteristic sequence generated by a linear feedback shift register of order 3 over GF(q). We will also propose an efficient algorithm to compute the (h-dk)th term of the characteristic sequence based on the knowledge of the kth term where k is unknown. Incorporating these results, we construct the ElGamal-like digital signature algorithm for the public-key cryptography based on the 3rd-order characteristic sequences which was proposed by Gong and Harn in 1999.