THE TWO-MESSAGE PROBLEM IN CIPHER TEXT AUTOKEY. PART I.
Jack Levine, Michael Willet · Cryptologia · 1979
This is Part I of a two-part paper on the problem of the decipherment of two identical messages enciphered by means of cipher-text autokey using the same plain and cipher alphabets for both messages. The initial-keys for the two messages are different, and with unknown lengths r, r′ respectively, where l≤r, r′≤m for a known integer m. In this Part I a simple hand-solution is described to determine r and r′, and some preliminary procedures outlined towards the reconstruction of the cipher alphabet. The methods used have been