I have posted this before and never saw any reply. The following sounded appealing to me because it gives public key features with private key cryptosystem speeds. Matrix Extensions of the RSA Algorithm Chih-Chwen Chuang and James George Dunham CRYPTO '90 Abstract A new matrix extension of the RSA algorithm is proposed which is based on the Cayley-Hamilton theorem and a one-way function. The security of this algorithm rests on that of the RSA algorithm and the one-way function. The computational efficiency of the new algorithm depends on the dimension of the marix. The most efficient implementation is the 2x2 case in which both the encryption and decryption use a single modulo arithmetic multiplication and single evaluation of the one-way function. later in the paper.. 'Under a chosen plaintext attack on the key, the security of the new algorithm is equivalent to that of the RSA algorithm. Under a known plaintext attack on the message, the security of the system rests upon that of the one-way function.' '..theyse public key cryptosystems hvae the potential of a fast implementation.' Has anyone looked into this paper? Has anyone implemented the cryptosystem explained in it?