An Account of Early Statistical Inference in Arab Cryptology

Recently discovered manuscripts reveal an early use of statistical inference in Arab cryptology in the eighth through twelfth centuries A.D. The manuscripts report that al-Kindi (801-873) used relative frequency analysis some 1100 years ago to decode messages, some 800 years before the correspondence between Pascal and Fermat. Among his many accomplishments, al-Kindi is the author of the oldest known book on cryptology. This article describes an early use of statistical methods for the cryptanalysis of encrypted messages.