Cryptography (1–5 Levels)

Cryptography (1–5 Levels)





Ravaan
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14 min read
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Sep 26, 2021
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Hey, I know you are probably scared of Cryptography, let’s be honest, you probably are not familiar or you think you know it but you don’t. A subject which I have learned as it only gets interesting once you get it. Let me teach you the wonders to this field and fast.
Prerequisites:
Level 1,2 (No prior knowledge)
Basic understanding of networks.(Level 3)
MATHS(upto 11th)- Later parts(Level 4,5)
Bit of programming.Level(4,5)
(LEVEL 4,5)Note: I will not cover the basics which come before cryptography. A checkpoint is made, if you are unfamiliar with any of the following, then you lack basic understanding of modern standards of security, I will try my best to make you understand this concept fast.
OID,CA, PKI,HSM,DRA,RA,Trust Model, Hierarchical Trust Model,Bridge Trust Model,Certificate Chaining, CRL, OCSP
Introduction and puzzles:(Level 1)
So what exactly is cryptography one may ask? Let’s take an example, you are sending a gift to your father, so you put it inside a box, now when you post it there is a problem. The mailman can simply open the box and steal the gift. The next idea would be to lock it and send the key separately to your father thereby preventing the mailman to open the box and steal the gift!
So you solved a problem, you prevented your gift or private information’s exposure to an unauthorized person(mailman)! Cryptography is similar but we do it in the digital world:

Mail = DATA/PAYLOAD
YOU = Sender
DAD = RECEIVER
MAILMAN = Unauthorized Person(HACKER)
Box = Protocol
LOCK = Algorithm
Key = Key
Cool! Now you know about Cryptography, script kiddies can leave now and rest keep reading because things will get interesting.
Cryptography before Jesus Christ(LEVEL 2)
Now let’s talk about digital cryptography, a bit of background is important. Julius Caesar used to substitute alphabets in his secret letters, for example he would substitute “D” by “T” thus DOG became TOG. Inspired by this we have ROT13 where every alphabet is moved by 13 places for example DOG is QBT, these are called substitution ciphers. There is a problem, the problem is everyone who knows the substitution can decrypt it and get the data.