ʻAfīf al-Dīn ʻAlī ibn ʻAdlān al-Mawsilī (Arabic: عفيف لدين علي بن عدلان الموصلي; 1187–1268 CE), born in Mosul, was an Arab cryptologist, linguist and poet who is known for his early contributions to cryptanalysis, to which he dedicated at least two books. He was also involved in literature and poetry, and taught on the Arabic language at the Al-Salihiyya Mosque of Cairo. He was in contact with various rulers of his time, and in this capacity he gained practical experience in cryptanalysis or the science of breaking encoded messages. He dedicated On Cryptanalysis, his only surviving work on the topic, to Al-Ashraf Musa (r. 1229–1237), the Ayyubid Emir of Damascus. He wrote three other books, including Al-Mu'lam (The Told [Book]), also on cryptanalysis, but it is now lost. On Cryptanalysis is a sort of guidebook for cryptanalysts, containing twenty sets of techniques he calls "rules". The methods contains more practical details than Al-Kindi's 8th century Treatise on Deciphering Cryptographic Messages—the earliest surviving work on cryptoanalysis—but lack its predecessor's theoretical background on cryptography. Among Ibn 'Adlan's original contributions were methods for breaking no-space monoalphabetic cryptograms, a type of ciphers which were developed to evade analysis techniques described earlier by Al-Kindi. In this treatise Ibn 'Adlan also includes a real-life example of a cryptogram that he deciphered and his full process in breaking it, which, in the words of the cryptographer James Massey, provides "the authentic experience of a highly skilled cryptanalyst."
Biography
'Afif al-Din 'Ali ibn 'Adlan was born in Mosul in 583 AH (c. 1187 CE). He was of an Arab origin and received education in Baghdad, including lessons on syntax by the grammarian Abu al-Baqa al-Ukbari. Subsequently, he lived in Damascus for a time, before became a teacher of the Arabic language at the Al-Salihiyya Mosque of Cairo until his death in 666 AH (c. 1268 CE). In addition to writing treatises on linguistics and cryptanalysis, he was considered an authority in literature and wrote poems himself. He was in contact with various rulers, and in this capacity he gained practical experience in cryptanalysis, which he calls hall al-mutarjam. One of these rulers was Al-Ashraf Musa (r. 1229–1237), the Ayyubid Emir of Damascus, for whom he dedicated his treatise On Cryptanalysis. He was also known by his multiple nisbas (descriptive epithets): al-Mawsili (of Mosul), al-Nahwi (the Grammarian) and al-Mutarjim (the Cryptoanalyst).
Works
Early Arabic bibliographies attributed three titles to him, including one on cryptanalysis, Fi hall al-mutarjam (On Cryptanalysis), also known as Al-mu'allaf lil-malik al-'Ashraf (The [Book] Written for King al-Ashraf). In addition, a reference in On Cryptanalysis points to another book, Al-Mu'lam (The Told [Book]), which is now lost, in which he describes algorithms for analysing cryptograms. His other two works were titled Al-Intihab li-kashf al-'abyat al-mushkilat al-i'rab and 'Uqlat al-mujtaz fi hall al-aljaz.
Background The practice and study of encrypting messages into ciphers, called cryptography, had existed since ancient times, practised by the Egyptian, Chinese, Indian, Mesopotamian, Greek, and Roman civilisations. In contrast, cryptanalysis, the science of breaking ciphers—in other words, recovering the plain message from an encrypted one—was founded in the early Arab-Muslim civilisation. The earliest surviving work found on the topic of cryptanalysis is the Risalah fi Istikhraj al-Mu'amma ("Treatise on Deciphering Cryptographic Messages") written by Al-Kindi (c. 801–873), an Arab scholar who also wrote on other topics including philosophy, astronomy, and medicine. Reports are also found on other works before al-Kindi, among the earliest of which is al-Mu'amma ("The Book of Cryptographic Messages"), written by al-Khalil ibn Ahmad in the 8th century, but they are now lost. Al-Kindi's book presents cryptanalysis techniques such as frequency analysis, which is to also be covered by Ibn 'Adlan's works.
On Cryptanalysis
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