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Shihāb al-Dīn Abū 'l-Abbās Aḥmad ibn ‘Alī ibn Aḥmad ‘Abd Allāh Banu Fazara al-Shāfiʿī better known by the epithet al-Qalqashandī (; 1355 or 1356 – 1418), was a medieval Arab Egyptians encyclopedist, polymath and mathematician. A native of the Nile Delta, he became a Scribe of the Scroll ( Katib al-Darj), or clerk of the Mamluk chancery in Cairo, Egypt. His magnum opus is the voluminous administrative encyclopedia Ṣubḥ al-Aʿshá.
The Ṣubḥ al-aʿshā was cited by David Kahn as the first published discussion of the substitution and transposition of ciphers, and the first description of a polyalphabetic cipher, in which each plaintext letter is assigned more than one substitution. The exposition on cryptanalysis included the use of tables of letter frequencies and sets of letters which cannot occur together in one word.
Kahn therefore cited it as the first work in human history that described cryptology, because it described both cryptography and cryptanalysis. Al-Qalqashandi quoted the text relevant to cryptology from the work of Ibn al-Durayhim (1312–1361) that was once considered lost. Later discoveries in Istanbul‟s Sulaimaniyyah Ottoman Archives did not just find the work by Ibn Duraihim, but also works of al-Kindi in the 9th century that is now considered the oldest work on cryptology.Kathryn A. Schwartz (2009): Charting Arabic Cryptology's Evolution∗, Cryptologia,33:4, 297-304
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