How Does Encryption Work, in Theory?
+Wednesday, February 19 2020
+ +There are many kinds of encryption used in our everyday communication. Online and offline, over the internet and in person. In this article, I will explain the basics of how encryption should work in theory. I explain in this article why encryption is important, and why you should care about it.
+ +We will start by looking at in-person, offline encryption.
+ +Cryptography We Do Everyday
+We encrypt things all the time without even thinking about it. +If you spend a significant amount of time with the same group of friends, your will tend of develop common codes that may not make sense to others outside the group. +For example: for years, my family called sombody falling from a sitting position “doing a Don”. There is a story of course—We knew a guy named Don who fell from his plastic beach chair in a rather hilarious way; “doing a Don” was born.
+ +These kind of minor dialects in speech are cryptographic in their own way. The truth is though, that we use cryptography much more than that!
+ +++ +“Is cryptography any different than talking? +We say something other than what we mean, and then expect everyone is able to decipher the true meaning behind the words. +Only, I never do…” — Adapted from a scene in The Imitation Game (p. 39-40)
+
How many times have you hinted, flirted, and innuendoed to try to say “I find you very physically attractive”? +Have you told your friend that always stinks to wear more deoderent? +Have you ever had someone say the words “I’m fine” when you know for certain that they are indeed not okay?
+ +| Words Said | +Meaning | +
|---|---|
| What can you do? | +I don’t want to talk about this anymore. | +
| I don’t want to overstay my welcome. | +I want to go home now. | +
| I don’t like them and don’t know why. | +They threaten my ego. | +
| Creepy | +Unattractive and friendly | +
All of these scenarios are perfect examples of lies encryption! If we have the key to these codes, we can start to understand what people really mean.
+Hopefully I have convinced you that you use deceit cryptography on a regular basis in your life, so let us consider what a basic encryption method might be:
Grade-School Encryption
+Back when I was in middle school I used to pass notes like these:
+ +PIC
+ +This is a messege encrypted using the Caesar cipher. This encryption technique was used by Julius Caesar during the reign of the Roman Empire to “encrypt messeges of military significance.”[1] +This is one of the oldest and simplest methods of encryption known to us today.
+ +
You can try this out yourself by moving some letters forward in the alphabet. +An ‘A’ turns into a ‘B’, ‘B’ into ‘C’, ‘C’ into ‘D’, et cetera. +In this case, “Hello!” would become “Ifmmp!” +That is just using a shift of one. You can use a shift of seven, for example, and then you would shift letters like so:
+ +-
+
A -> +7 -> H
+ Q -> +7 -> X
+ T -> +7 -> A
+
We should wrap-around to the beginning of the alphabet if there are no letters left.
+ +Example of a Caesar Cipher
+Let’s setup a little story to illustrate the problems of encryption. We will have three characters:
+ +-
+
- Alice, a little girl with feelings for Bob +
- Bob, a young boy with an addiction to pancakes +
- Eve, a wee jealous girl scout who sits between Bob and Alice +
Alice really likes Bob and wants to tell Bob her feelings, so she writes “I love you, Bob! Please eat healthier!” on a sticky note. +She passes it to Eve, so Eve can pass it to Alice’s love interest. +However, in an unfortunate turn of events Eve reads the note herself, and decides not to give it to Bob.
+ +Oh the horror! Alice is without young love! How could she remedy this so that Bob can read her messege, but evil Eve can not? +Let’s use the Caesar cipher to fix this problem.
+ +Let us assume that Alice and Bob already have a shared key, 7 for example. To encrypt this messege, we should shift our letters seven letters forward in the alphabet—just like the example above.
+ +PIC2
+ +Now Alice’s messege reads “P svcl fvb, Ivi! Wslhzl lha olhsaoply!”
+ +Now, when Alice sends her Romeo a little note, all he has to do is decrypt the text by shifting the letters down by 7. +Here is a site which can do longer pieces of text for you instead of doing it manually.
+ +Problems
+ +Before the two love-birds start smooching on the branch of a big pine tree in the schoolyard, perhaps we should consider some problems with the Ceasar cipher.
+ +It is Very Easy to Break
+ +Even Eve with her measly grade 4 math skills could easily start going through this messege with pen and paper and figure out any combination in a couple hours at maximum. +Imagine how easy this is for a computer? +This could be broken in a few microseconds even on an older processor like the Intel Core 2 Duo.
+ +No Secure Way of Sharing Keys
+ +We assumed in our previous example that Bob and Alice already have a shared key (seven) to encrypt and decrypt all of their messeges. +If Bob and Alice did not have a previous friendship and time to share secrets of this sort, there is no way to share their key with eachother without Eve also knowing. +This would defeat the entire purpose of obscuring the messege in the first place.
+ +Universal Vulnerability of Messeges
+ +Every messege sent between the two parties uses the same code to encrypt and decrypt. If someone finds out the code once, all previous communications are comprimised.
+ +Better Encryption Methods
+ +To combat the issues with easily breakable, shared-key cryptography, we can turn to the beautiful beast that is Asymetric Cryptography. +I will discuss this more in another article, but for the technically inclined:
+ +-
+
- RSA/EC provides very large cryptographic keys. It would be impossible for a human to encrypt or decrypt a messege manually. +
- Asymetric cryptography provides four keys, instead of just one; stopping evesdroppers from listening in on your secret conversations—even if you do not have the change to exchange keys in advance. +