TheCodeBreakers
succeeded in its task. Its author, who lived in Egypt, was Shihab al-DIn
abu '!-'Abbas Ahmad ben 'Ali ben Ahmad 'Abd Allah al-Qalqashandi. The
cryptologic section, "Concerning the concealment of secret messages
within letters," has two parts, one dealing with symbolic actions and
allusions, the other with invisible inks and cryptology. Qalqashandi
attributed most of his information on cryptology to the writings of Taj ad-
Din 'All ibn ad-Duraihim ben Muhammad ath-Tha'alibi al-Mausill, who
lived from 1312 to 1361 and held various teaching and official posts
under the Mamelukes in Syria and Egypt. Except for a theological
treatise, none of his writings is extant, but he is reported to have
authored two works on cryptology.
After explaining that one may write in an unknown language to obtain
secrecy, Ibn ad-Duraihim, according to Qalqashandi, gave seven systems
of ciphers. This list encompassed, for the first time in cryptography, both
annaabi.ee 
