APPLICATIONS OF THE DRAZIN INVERSE TO THE HILL CRYPTOGRAPHIC SYSTEM. PART I.
Jack Levine, Robert E. Hartwig · Cryptologia · 1980
It is shown by means of examples how formulas developed by Hartwig and based on the Drazin matrix inverse can be used to serve as key-matrices in an autokey formulation of the Hill cryptographic system wherein the key-matrix is a function of the actual plaintext being enciphered rather than of previously enciphered plaintext (as is customary in plaintext autokey). A method for obtaining the Drazin inverse over the general ring Zt is explained and a Table of Drazin inverses applicable to matrices through fifth order is given. Several problems are presented for the reader to solve. In practical applications the encipherment and decipherment would be carried out by computer.