Egyptians used encryption as a way to communicate messages in obscure form. Julies Caesar wrote his strategic letters in cipher, that is, by so changing the order of the letters of the alphabet. He replaced every letter with the fourth letter; A becomes D, Z becomes C and so on.
A very smart way to send a concealed message is to to shave the head of the messenger, wait till his hair grows back again and send him to the recipient. I am not sure who used this technique but I it is definitely very intelligent.
A very common way to decipher messages is known as frequency analysis:
One way to solve an encrypted message, if we know its language, is to find a different plaintext of the same language long enough to fill one sheet or so, and then we count the occurrences of each letter. We call the most frequently occurring letter the ‘first’, the next most occurring letter the ‘second’ the following most occurring letter the ‘third’, and so on, until we account for all the different letters in the plaintext sample. Then we look at the cipher text we want to solve and we also classify its symbols. We find the most occurring symbol and change it to the form of the ‘first’ letter of the plaintext sample, the next most common symbol is changed to the form of the ‘second’ letter, and the following most common symbol is changed to the form of the ‘third’ letter, and so on, until we account for all symbols of the cryptogram we want to solve [source].
The first known recorded explanation of frequency analysis (indeed, of any kind of cryptanalysis) was given in the 9th century by Al-Kindi, an Arab polymath, in A Manuscript on Deciphering Cryptographic Messages. It has been suggested that close textual study of the Qur’an first brought to light that Arabic has a characteristic letter frequency. Its use spread, and similar systems were widely used in European states by the time of the Renaissance [source].
I can’t find an answer of how a nation that used to be pioneer in science is now tailing behind every other nation in a dramatic way. Europe was a pioneer in science before WWI and WWII and they managed to get back on track after the war. Japan as well after the atomic bomb they stood up even better than they used to.
The question is why Arabs still performing extremely bad in science? I know it is not the case when it comes to individuals because Arab scientists and researchers are doing great in Europe and the United States. We have the money and we have the brains but, unfortunately, we fail in leadership. Without good leadership we can’t build a successful organization or nation.