CISSP D3 Preview | The History of Cryptography – Part 1

In this lecture, we are going to talk about the history of cryptography and you might think, wait, what, how is that possibly relevant?
And it is relevant for two reasons.
First off, learning how something evolved and how it has been used over time can make you understand why we do some of the things we do today.
And secondly, and much more important, it’s on the exam.
This is something you might see in some of your questions, and it’s easy to learn.
It’s stuff you just need to memorize.
So these are easy win points.
Take them and be happy for them.
There are going to be plenty of questions on the exam that are convoluted, difficult, and where you end up having to pick the best of two possible right answers.
So the few times the exam is going to give you easy wins, take it.
We’re going to start out with the Spartan Scytale, and it is really just taking a piece of cloth and wrapping that cloth around a stick of a certain diameter and then writing your message.
Once you’re done writing the message, you remove it from the stick and then send it to the receiver.
Now, if someone else intercepts this message, they’re just going to see a long piece of cloth or parchment with letters that doesn’t make a lot of sense, even if for some reason they decide to wrap that around a stick, if that stick is not the exact same diameter, then it’s not going to line up and they can’t read the text.
Here, the stick of the same diameter is the shared secret that we use for our symmetric encryption.
Next up, we have Ceasar Cipher.
This is a substitution cipher.
Here we have our plain text message, and we then moved the letters a couple of rows over on the alphabet.
In the example you see over here on the right, you can see all the letters have moved three characters to the left.
So if our plain text message is “pass the exam”, moved three letters back, it would be “mxpp qeb buxj”, super super simple, but again, at the time, it was effective.
Next up, we have the Vigenère cipher.
It is a polyalphabetic cipher named after Blaise de Vigenère, a French cryptographer living in the 16th century.
If you look at the image over here on the right, you can see the English alphabet repeating both on the X and the Y axis.
And that square is called a Vigenère square, on both the X and the Y axis, the alphabet repeats 26 times.
On the X axis, you write the plaintext and then you write the key on the Y axis.
Here, let’s say our plaintext is “CISSP”, and the key is “Thor”.
That would make the ciphertext “VPGJI”.
When it was in active use, obviously both the key and the plaintext would be a lot longer.
But you get the idea right?
For the C, you go to the zero on the X axis and then you go down to the first of the key, that’s T, where they intersect, it’s a V, then you do that for the rest of the plaintext.
Now let’s take a look at cipher disks.
A cipher disk is two concentric disks with alphabets on them.
And concentric just means round.
One disk is bigger, the other is smaller.
If it is monoalphabetic or static, just like we looked at before, then T, for instance, will always be a D, but normally you would turn the inner disk, a certain number of letters in one direction after so many uses.
So for every five, 10, 20 letters, we might rotate the inner disk three spaces to the right.
Then we do another five letters in that position and then we rotate it again.
Which brings us to the Enigma.
Before and during the Second World War, Germany used the Enigma coding machine for all the secure communication.
They would encrypt it, then they would send it and then the receiver would decrypt it.
You may have seen the movie The Imitation Game, I personally thought it was an awesome movie.
If you haven’t seen it, go find it.
It’s the story about how a British group of scientists under the leadership of Alan Turing broke the Enigma encryption and how that would change the outcome of the war.
And to be fair here, there were multiple teams of people that broke the enigma.
On top of the team in the UK with Alan Turing, there was also a U.S. team of female scientists that broke the enigma as well.
You should also know there were two versions of the Enigma.
Early on before the Second World War, the Enigma had three rotors, that was broken by the Polish military when the Germans realized that.
The three rotor version was compromised.
They just added one more rotor, making it exponentially harder to break.
When it had three rotors, the options could be 26 x 26 x 26.
That gives us just over 17,500 different combinations.
When they added the fourth rotor that now changed the possible combinations to over 450,000.
So you can see what I mean when I say it was exponentially harder to break.
But as we know, it was eventually broken.
And if you have read up on it, if you have seen the movie, then, you know, they kept it a secret.
They only use the information for very, very critical targets.
If the Germans had started seeing unexplainable losses everywhere, then at some point they would figure out they were compromised.
By not acting on everything they decrypted, but only acting on the most important, they were able to conceal that they had broken the enigma.
And with the critical information they got, they were able to end the war years before it would have and saved millions of lives.
Which then brings us to Purple.
And Purple is the US name for a Japanese rotary based system very similar to the enigma.
And it was broken both by the US, the UK, and Russia.
It had three rotors, just like the Enigma did early on.
But as we know from the Enigma, three rotors was easy to break.
When Russia had broken the encryption and learned that Japan was not planning to attack Russia, they then moved the majority of their Eastern Front troops to Moscow to fight the Germans because they knew they were not a target.
They had decoded several messages saying Japan was going for Southeast Asia.
And with that we are done with this lecture.
We will finish up the history of cryptography in the next lecture.