| |
|
|
Al-Kindi was a prolific writer, the total number of
books written by him are roughly 270 in number(1), the
prominent of which were divide as such:
◙ Astronomy Philosophy
◙ Medicine Physics
◙ Music Psychology
◙ Arithmetic Logic
◙ Geometry Linguistics
◙ Statistics Cryptography (the science of obscuring
information to make it unreadable without special
knowledge)
But his greatest treatise, which was only rediscovered
in 1987 in the Sulaimaniyyah Ottoman Archive in
Istanbul, is entitled
"A Manuscript on Deciphering
Cryptographic Messages” |
|
| |
He introduced cryptanalysis
techniques (The science of unscrambling a message
without knowledge of the key), classification of
ciphers, Phonetics and syntax, and most importantly
described the use of several statistical techniques for
Cryptanalysis.
This work antedates other Cryptanalysis references by
300 years and Predates writings on probability and
statistics by Pascal and Fermat by nearly 800 years…….
Cryptanalysis could not have been invented until a
civilisation had reached a sufficiently sophisticated
level of scholarship in several disciplines including
linguistics, statistics and mathematics.(2)
And who better grouped and mastered all these
disciplines than Al’Kindi:
Al-kindi was born in Kufa in modern day Iraq, which was
at the time home to the most literate and learned
society in the world. He was from the elite and his
father was the governor of Kufa. His later studies were
in Baghdad where he occupied some government position.
He was also appointed as a personal tutor for the
Caliphs son, and then latter a researcher at (Bayt al-Hikam)
the ‘House of Wisdom’; a centre for intellectual
development studying many previous civilisations such as
the Egyptians, Babylonians and Greeks….
However….
As well as the use of encryption to protect
governmental, tax, and army bureaus, some of these old
manuscripts that were being studied were encrypted,
which motivated the code breakers to crack the ciphers
and reveal the secrets within.
In fact, cryptography was one of the great motivations
for the development of the science of statistics, and at
the same time is one of the crowning achievements of
statistics. (5)
|
|
|
|
■
Methods Of Cryptology
Randomness is an essential consideration in cryptology.
The goal in designing a cryptosystem is to make the
cipher-text appear as a random jumble of letters, which
cannot be deciphered without knowledge of the secret
order that lies within.
When a message is encrypted it mainly takes two basic
forms of transformations:
1. Transposition (the letters of the plane text are
jumbled up) , and the more popular and diverse method of
2. Substitution (letters are substituted for other
letters or numerals)
Using transposition meant that words kept their
identities but lost there positions; i.e the word
cryptology becomes rpotcolygy
Using Substitution means that the letter retains
position but totally losses identity; and therefore is
the favoured option
Methods Of Cryptology:
substitution cipher
The cipher alphabet can be any rearrangement of the
plain alphabet. This can generate an enormous number of
distinct modes of encryption.
To construct a cipher alphabet, the first letter could
be any of the 26 letters. The second letter could be any
of the remaining 25 letters. The third letter could be
any of the remaining 24 letters, and so on. The total
number of permutations is 26 x 25 x 24 x ... ...x 1
(otherwise written as 26!)
|
|
|
|
■
Methods Of Cryptology:
substitution cipher
There are 403,291,461,126,605,635,584,000,000
such rearrangements, which gives rise to an equivalent
number of distinct cipher alphabets. Each cipher
alphabet is known as a key…….
If the message is intercepted by an unintended party,
who correctly assumes a substitution ciphers has been
used, they are still faced with the impossible challenge
of checking all possible keys. If they could check one
of these possible keys every second, it would still take
roughly
one billion times the lifetime of the universe to check
all of them and find the correct one.This simple brute
force approach clearly does not work and kept
substitution safe for centauries.
Back in Baghdad however, Schools for theologians had
been set up and they were scrutinising the Quran and
counting the frequencies of words contained in each
revelation, this was done in order to establish the
chronology of the different revelations. The theory was
that certain words had evolved amongst the people
recently, and hence if a revelation contained a high
number of these new words, this would indicate that it
came later in the chronology…
|
|
|
|
|
- - - - - - - - -
- - - - - - - - - - - - - - - - - -- - |
|
|
| |
|
Al-Kindi
Created a table accounting the frequency of all the
letters in the alphabet,
|
letter |
frequency (%) |
letter |
frequency (%) |
|
a |
8.167 |
n |
6.749 |
|
b |
1.492 |
o |
7.507 |
|
c |
2.782 |
p |
1.929 |
|
d |
4.253 |
q |
0.095 |
|
e |
12.702 |
r |
5.987 |
|
f |
2.228 |
s |
6.327 |
|
g |
2.015 |
t |
9.056 |
|
h |
6.094 |
u |
2.758 |
|
i |
6.966 |
v |
0.978 |
|
j |
0.153 |
w |
2.360 |
|
k |
0.772 |
x |
0.150 |
|
l |
4.025 |
y |
1.974 |
|
m |
2.406 |
z |
0.074 |
|
|
Frequency
analysis was therefore for the first time ever documented |
|
The Other side of the same coin, Cryptanalysis:
The Break Through!!
Al-Kindi was also involved in this process and went even
further by discovering linguistic phenomena while
practicing Lexicography (principles and practices of
dictionary making) (4)
For example he recognized that certain letters were more
often used in natural languages ,(like the letter E and
A in the English language for example) while others were
used rarely, (like the letter Z).
■
Frequency analysis
Al-kind had found a weakness in the cryptic messages and
exploited this fact ; Basically, that languages are
non-random in nature.
He summarises the relevance of using the frequency table
to break message’s in two paragraphs:
“One way to solve an encrypted message, if we know the
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 the first, the next most
occurring the second, the following the third, and so
on, until we account for all the different plain letters
in the plaintext sample.
Then we look at the ciphertext we want to solve and we
classify its symbols. We find the most occurring and
change it to the form of the first letter of the plain
text sample, the next most common symbol is changed to
the form of the second letter, and so on, until we
account for all symbols of the cryptogram we want to
solve…”
The first page of al-Kindi's manuscript "On Deciphering
Cryptographic Messages", containing the oldest known
description of cryptanalysis by frequency analysis.
|
|
|
He also took the Law of large numbers
in to consideration as he recognised that for a messages
to be successfully deciphered it had to be long enough
to be relevant.
And only using the frequency substitution method on
short text would not always prove sufficient, so he
devised other techniques by exploiting the position of
the letters
Al-kindi provided statistical information on the
frequencies of two-letter groups (called bigrams) and
three-letter groups (trigrams). For example The most
commonly occurring bigram in English is ``he''; the most
frequent trigrams are ``the'' and ``and”. |
|
| |
|
To conclude this he made Contact Charts identifying the
relevance of letter contacts, (which letters touch each
other and how many different ones, and does it come
before or after certain letters more than others). He
used tally charts with tally's above the letter to
denote a proceeding letter and below the letter for
letters that came after the subject letter.
■
Cryptology nowadays
From preventing the plot of Mary Queen of Scots in
trying to assassinate queen Elizabeth in the 16th
centaury, to cracking the zimmermann telegram in world
war one (which was instrumental in bringing America in
to the war), and the Enigma code in world war two
(estimated to have significantly shortened the war),
cryptanalysis has undoubtedly influenced the course of
history.
And with the advent of the Internet and increased demand
for secure transactions cryptology is a hot topic of the
day!!
■
Famous Quote:
“We ought not to be embarrassed of appreciating the
truth and of obtaining it wherever it comes from, even
if it comes from races distant and nations different
from us. Nothing should be dearer to the seeker of truth
than the truth itself, and there is no deterioration of
the truth, nor belittling either of one who speaks it or
conveys it."
Abu Yosuf Al-Kindi
References
1. Al – Ehwany, Ahmad Fouad. (1996) “Al Kindi” A history
of Muslim Philosophy, Vol. 1. New Delhi: Low price
publications. pp. 421 – 434
2. Singh, Simon, The secret History of Secrecy, 2000
3. Scientific weather forecasting in the middle ages :
the writings of Al-Kindi : studies, editions, and
translations / by Gerrit Bos and Charles Burnett
4. David Kahn, The Codebreakers
5. http://www.math.okstate.edu/~wrightd/crypt/crypt-intro/node9.html
6. www.muslimheritage.com |
 |
|
- - - - - - - - -
- - - - - - - - - - - - - - - - - -- - |
|
|
| |
|
|
|
|
|
| |
|
| Main |
About ICM |
Editorial Board
|
Contents
|
Terms |
Writers |
Gallery |
Links |
Archive |
Contact us |
|
|
©2006 Islamic Civilization Magazine.
All rights reserved. |
