encryption basics 3

encryption_basics3.py

#UPPERCASE LETTERS START AT 65 (ord("A"))
#LOWERCASE LETTERS START AT 97 (ord("a"))
#This can make it hard to work with Unicode ordinals.
#Because of this, it is often easier to 'normalise'
#Unicode characters to actual alphabet placements:

c_normal = ord("c") - ord("a")
print(c_normal) #prints 2
# 'c' is the 2nd element (or 3rd letter) in the alphabet:
# a = 0
# b = 1
# c = 2
# d = 3
# etc. so for the alphabet placement of 'e':
e_normal = ord("e") - ord("a")
print(e_normal) #prints 4

#If, in encryption, i wanted to shift
#character 'c' (2) by character 'e' (4),
#i would get 2+4=6, which is character 'g':

g_normal = c_normal + e_normal 
print(chr(g_normal + ord("a"))) #prints 'g'

#If i was to shift character 'x' (23) by
#character 'g' (6), i'd end up at element 29
#of the alphabet, which doesnt exist.

#In this case, i'd wrap around to the start
#of the alphabet again by using modulo (%):
#(23+6)%26 = 3.. or character 'd':

x_normal = ord("x") - ord("a")
d_normal = (x_normal + g_normal) % 26
print(chr(d_normal + ord("a"))) #prints 'd'

#the alphabet offers a base-26 system, which
#offers more combinations than our decimal system
#which is base-10. In our decimal system, after 9,
#we go back to 0. Which is the same in the alphabet
#if we go from z >> a (or a >> z). Thats why you will
#see the modulo (%) operator alot with the number 26.
#this lets us see how many letters past (remainder) 26
#we have gone.

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