Shihāb al-Dīn Abū 'l-Abbās Aḥmad ibn ‘Alī ibn Aḥmad ‘Abd Allāh al-Fazārī al-Shāfiʿī better known by the

epithet An epithet (, ), also a byname, is a descriptive term (word or phrase) commonly accompanying or occurring in place of the name of a real or fictitious person, place, or thing. It is usually literally descriptive, as in Alfred the Great, Suleima ...

al-Qalqashandī (; 1355 or 1356 – 1418), was a medieval

Arab Arabs (, , ; , , ) are an ethnic group mainly inhabiting the Arab world in West Asia and North Africa. A significant Arab diaspora is present in various parts of the world. Arabs have been in the Fertile Crescent for thousands of years ...

Egyptian ''Egyptian'' describes something of, from, or related to Egypt. Egyptian or Egyptians may refer to: Nations and ethnic groups * Egyptians, a national group in North Africa ** Egyptian culture, a complex and stable culture with thousands of year ...

encyclopedist An encyclopedia is a reference work or compendium providing summaries of knowledge, either general or special, in a particular field or discipline. Encyclopedias are divided into articles or entries that are arranged alphabetically by artic ...

polymath A polymath or polyhistor is an individual whose knowledge spans many different subjects, known to draw on complex bodies of knowledge to solve specific problems. Polymaths often prefer a specific context in which to explain their knowledge, ...

and

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

. A native of the

Nile Delta The Nile Delta (, or simply , ) is the River delta, delta formed in Lower Egypt where the Nile River spreads out and drains into the Mediterranean Sea. It is one of the world's larger deltas—from Alexandria in the west to Port Said in the eas ...

, he became a Scribe of the Scroll (''Katib al-Darj''), or clerk of the

Mamluk Mamluk or Mamaluk (; (singular), , ''mamālīk'' (plural); translated as "one who is owned", meaning "slave") were non-Arab, ethnically diverse (mostly Turkic, Caucasian, Eastern and Southeastern European) enslaved mercenaries, slave-so ...

chancery in

Cairo Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

. His

magnum opus A masterpiece, , or ; ; ) is a creation that has been given much critical praise, especially one that is considered the greatest work of a person's career or a work of outstanding creativity, skill, profundity, or workmanship. Historically, ...

is the voluminous administrative encyclopedia ''Ṣubḥ al-Aʿshá''.

''Ṣubḥ al-aʿshā''

''Ṣubḥ al-Aʿshá fī Ṣināʿat al-Inshāʾ'' ('The Dawn of the Blind' or 'Daybreak for the Night-Blind regarding the Composition of Chancery Documents'); a fourteen-volume encyclopedia completed in 1412, is an administrative manual on geography, political history, natural history, zoology, mineralogy, cosmography, and time measurement. Based on the ''Masālik al-abṣār fī mamālik al-amṣar'' of

Shihab al-Umari Shihab al-Din Abu al-Abbas Ahmad Ibn Fadlallah al-Umari (), commonly known as Ibn Fadlallah al-Umari or Ibn Faḍl Allāh al-‘Umārī (1301 – 1349) was an Arab historian born in Damascus. His major works include ''at-Taʾrīf bi-al-muṣ� ...

, it has been called "one of the final expressions of the genre of

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

administrative literature". Selections on "Seats of Government " and "Regulations of the Kingdom " from Early Islam to the Mamluks' have been published separately. 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 A polyalphabetic cipher is a substitution cipher, substitution, using multiple substitution alphabets. The Vigenère cipher is probably the best-known example of a polyalphabetic cipher, though it is a simplified special case. The Enigma machine i ...

, in which each

plaintext In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. This usually refers to data that is transmitted or stored unencrypted. Overview With the advent of comp ...

letter is assigned more than one substitution. The exposition on

cryptanalysis Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic se ...

included the use of tables of

letter frequencies Letter frequency is the number of times letters of the alphabet appear on average in written language. Letter frequency analysis dates back to the Arab mathematician Al-Kindi (c. AD 801–873), who formally developed the method to break ci ...

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 ʿAlī ibn Muḥammad ibn ʿAbd al-ʿAzīz Ibn Futūḥ ibn Ibrahīm ibn Abū Bakr (; 1312–1359/62 CE), known as Ibn Durayhim al-Mawsilī () was an Arab writer, mathematician, cryptologist and scribe. Cryptology Ibn al-Durayhim gave detailed ...

(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 Abū Yūsuf Yaʻqūb ibn ʼIsḥāq aṣ-Ṣabbāḥ al-Kindī (; ; ; ) was an Arab Muslim polymath active as a philosopher, mathematician, physician, and music theorist Music theory is the study of theoretical frameworks for understandin ...

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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''Ṣubḥ al-aʿshā''

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Further reading