American Mathematical Monthly Vol.36, June–July 1929, pp. 306–312. (PDF) Lester S. Hill, Concerning Certain Linear Transformation Apparatus of Cryptography, The American Mathematical Monthly Vol.38, 1931, pp. 135–154. Jeffrey Overbey, William Traves, and Jerzy Wojdylo, On the Keyspace of the Hill Cipher, Cryptologia, Vol.29, No.1, January 2005, pp59–72. (CiteSeerX) (PDF) External links "Hill Cipher Web App" implements the Hill cipher and shows the matrices involved "Hill Cipher Explained" illustrates the linear algebra behind the Hill Cipher "Hill's Cipher Calculator" outlines the Hill Cipher with a Web page Classical ciphers