E-CES, 212-81, Module 1, History of Cryptography - C839 with 100- correct answers

E-CES, 212-81, Module 1,
History of Cryptography -
C839 with 100% correct
answers
Cryptography - answer Science of *altering communication* so that
it cannot be understood without a *key*


a.k.a. SECRET WRITING


Obfuscating a message


Mono-Alphabet Substitution Cipher - answer Algorithms that simply
*substitute one character of cipher text for one character of plain
text*, these are the most primitive algorithms


Types Include: *CARA*
*C*aesar
*A*ffine
*R*ot13
*A*tBash


Caesar Cipher - answer Every letter is simply *shifted* a *fixed
number* of places to the left or to the right


*Mono-Alphabet Substitution Cipher*


IE: One shift to the left: a.k.a. (-1)

, I Like Computers - Start
H Khjd Bnlotsdqr - Finish


Atbash Cipher - answer *Hebrew cipher* which *substitutes* the
*first letter of the alphabet for the last*, and the second letter for
the second-to-last, in other words, it simply reverses the alphabet.


*Mono-Alphabet Substitution Cipher*


IE:
A cat sleeps - Start
Z xzg hovvkh - Finish


Affine Cipher - answer Any *single substitution alphabet ciphers*
where *each letter* in the alphabet is *mapped to* some *numeric
value*, permuted with some relatively simple mathematical
function, and *then converted back to a letter.*


*Mono-Alphabet Substitution Cipher*


IE:
*M* is the size of the alphabet = 26
The *x* represents the plain text letter's numeric equivalent
The *b* is the shift
The *a* is some multiple


ax + b(modM) - *Affine*
1x + 3(mod 26) - *Caesar*