1. Cryptography & Cryptanalysis
Classics

2. The Evolution of Secret Writing
1. Steganography

3. 2. Cryptography “The aim of cryptography is not to hide the existence of a message, but rather to hide its meaning, a process known as encryption”

4. Transposition
Cow cow, cwo, owc, ocw, wco, woc.
Substitution
c X
o G
w P
cow XGP

5. “For example, consider this short sentence” has 50,000,000,000,000,000,000,000,000,000,000 rearrangements.

6. Rail Fence Transposition

7. Spartan Scytale

8. meet at midnight CUUZ VZ CGXSGIBZ
Substitution
Cipher
meet at midnight CUUZ VZ CGXSGIBZ

9. CAESAR Shift Cipher

11. Kerckhoffs’ Principle: The security of a cryptosystem must not depend on keeping secret the cryptoalgorithm. The security depends only on keeping secret the key.

12. JULIUS CAESAR JULISCAER

13. Muslims Cryptanalysis Monoalphabetic Substitution Cipher a # b +
The Science of Unscrambling a message without knowledge of the key.

14. “A Manuscript on Deciphering Cryptographic Messages”
Frequency Analysis
al-Kindı’s
“A Manuscript on Deciphering Cryptographic Messages”

15. English

19. P is a consonant.

20. Combination OO appears twice, whereas XX does not appear at all.
X and Y appear on their own in the ciphertext. (a and I are the only English word that consisit of a single letter)
In the English language, the letter h frequently goes before the letter e (as in the, then, they, etc.), but rarely after e. h

21. O=e, X=a, Y=i, B=h. the most common three-letter words in English are the and and, and these are relatively easy to spot—Lhe, which appears six times, and aPV, which appears five times. P=n, V=d, L=t.

22. Every word has a vowel in it, so C in Cn is a vowel
Every word has a vowel in it, so C in Cn is a vowel. The only vowels remaining are o and u. u does not fit so C = o.
We also have the word Khe, which implies that K represents either t or s. But we already know that L = t, so it becomes clear that K = s.
thoMsand and one niDhts thousand and one nights

23. A VOID BY GEORGES PEREC AVOIDBYGERSPC

25. 1. Begin by counting up the frequencies of all the letters in the ciphertext. About five of the letters should have a frequency of less than 1 percent, and these probably represent j, k, q, x and z. One of the letters should have a frequency greater than 10 percent, and it probably represents e. If the cipher-text does not obey this distribution of frequencies, then con-sider the possibility that the original message was not written in English. 2. the most common repeated letters are ss, ee, tt, ff, ll, mm and oo. 3. The only one-letter words in English are a and I. The commonest two-letter words are of, to, in, it, is, be, as, at, so, we, he,by, or, on, do, if,me,my, up, an, go, no, us, am . The most common three-letter words are the and and.

26. Code
One of the simplest improvements to the security of the monoalphabetic substitution cipher was the introduction of nulls, symbols or letters that were not substitutes for actual letters, merely blanks that represented nothing.

29. The Pigpen Cipher

30. New Ciphers
Leon Battista Alberti
hello AFPAD

36. L1-L2-L3-L4-L5

40. EMILY

41. THANK YOU!!