Al-Kindī, Calligraphy and Cryptography in 9th c Middle East

This is one folio from the precious “Blue Qur’an,” dating from about 850-950 CE. The indigo-dyed parchment is adorned with gold and silver lettering, a treasured example of the heights to which the Arabic-speaking Muslim world brought the art of calligraphy. The era in which this copy of the Qur’an was written overlaps with the lifetime of Abū Yūsuf Ya’qūb ibn ‘Ishāq as-Sabbāh al-Kindī (c. 801-873 CE), a polymath scholar whose own calligraphy was famed in his day:

“I do not know any other form of writing in which the letters undergo so much beautifying and refining as they do in Arabic writing,” scribed Al-Kindī. Perhaps it was his close attention to the patterns created in the practice of calligraphy that fostered in him a talent for cryptography. Nowadays, cryptography is super important for preventing (or attempting to prevent) online data theft. For Al-Kindī, it was an intellectual exercise, one that he excelled in with great originality and success.

Al-Kindī wrote _A Manuscript on Deciphering Cryptographic Messages_, which dealt with cryptanalysis techniques, cipher types, phonetics, syntax, and computational linguistics. Honestly that list doesn’t make much sense to me (I am no cryptographer), but you don’t need to be a statistician to understand that he was the first known person to use frequency analysis as a way of breaking codes. Look at the Arabic in the photo above, and you might see repetitions of the strokes that make up the Arabic alphabet. As in English, certain letters appear with greater frequency than others, with shorter words or certain phonetic sounds more likely to coincide with certain letters. Al-Kindī figured this out. Once you know the frequency of a certain letter, you can experiment by plugging in the letters you expect to be in certain spots. Trial-and-error of course is partly what you have to do experiment with, a process that is now exponentially easier with modern computers.