How did the Enigma Machine work? - YouTube

- [Jared] This is the Enigma machine.

It looks like a typewriter but it has

a very different purpose.

During World War II it was used to keep messages secret

or in other words encrypted.

In this video, we'll look at why the Enigma machine exists,

how it was used and then we'll take a look at the inside

to see how the mechanism works.

(electricity buzzes)

This video is sponsored by Brilliant,

a fun and interactive way to learn math and science.

Towards the end of this video

we'll take a closer look at their website and app.

While making this video I had a lot of help

from enigmamuseum.com.

These guys took a part in actual enigma machine

and showed me what's on the inside,

behind the panels, all the inside wiring

and how each mechanical piece works.

This would have taken a lot longer to 3D model

and animate without their help.

So big thanks to enigmamuseum.com

and now let's get to some animation.

To really understand the Enigma machine

we need to understand something called encryption.

Let's use an example.

Say we have two friends, Alice and Bob.

Alice wants to send a message to Bob

however, Alice doesn't want anyone else

to be able to read this message such as Eve.

Just as an example we'll keep the message really simple.

Alice will need to scramble the contents of the message.

This is called encryption.

It looks like a bunch of random letters

and if Eve gets a hold of it then she won't be able

to understand it.

When the message gets to Bob he needs

to unscramble the message.

This is called decryption.

Now he can read the original message.

Alice and Bob need to agree on a way

to encrypt and decrypt their messages.

A real simple way to do this is called a Caesar cipher.

This involves shifting all the letters in the message

three spaces to the right in the alphabet

so an H becomes a K, an E becomes an H,

an L becomes an O, an L becomes another O,

and an O becomes an R.

Now the message looks like gibberish,

A bunch of random letters.

When Bob gets the message all he has to do

is take each letter and move it back three spaces.

This will give him the original message

so he can read it again.

Now Eve in the middle, as long as she doesn't know

how the messages were encrypted

she won't be able to read any one of them.

During war encryption is extremely important.

Commanding officers need to be able to get messages out

to the troops on the battlefield

but they don't want the enemy to be able

to understand these messages.

Nowadays encryption is performed by computers

but this wasn't always the case.

The Enigma machine was used to encrypt and decrypt messages.

You can think of this as a very sophisticated

letter scrambler.

It was invented in the early 1900s

and then most famously, it was used

by the German military in the 1930s

and throughout World War II.

This is the keyboard with 26 letters.

And this is the lamp board which also has 26 letters

but these letters can light up.

Each time you press a letter on the keyboard,

a letter on the lamp board lights up,

but it will always be a different letter

than the one that was pressed.

There are usually two people involved

when the machine is used, one person to type in the letters

and another person to write down the letters

that appear on the lamp board.

Let's use our example from earlier.

Type in each letter and write down the letters

that appear on the lamp board.

Now we have our encrypted message,

the scrambled letters that nobody can read.

This message is sent usually by radio using morse code.

The person who receives this message also

has their own Enigma machine.

To decrypt the message or unscramble it

they type in the letters on the keyboard

and write down which letters appear

on the lamp board and out comes the original message.

The Enigma machine was used for both

encryption and decryption.

The person sending the message needs a machine

and the person receiving the message

also needs a machine to be able to read it again.

So how does the Enigma machine know which letters

to give you?

Maybe you press an A and outcomes an H.

How does it do that?

Well, part of the answer is electricity.

Let me show you a simple example.

We have a battery, some wires, and then something

that uses electricity in this case, a light bulb.

This is called a circuit.

It's a closed loop for the electricity to flow.

But if there's a break in the wire,

then the light bulb turns off.

If we put a switch in here, now we can easily turn

the light bulb on or off.

There has to be a complete path for the electricity to flow.

Now let's add another path, one more switch,

and a light bulb.

Now we can turn on two different light bulbs

depending on which switch we turn on,

there's a different path through the wires.

We could expand this even more,

more switches and more light bulbs.

Now, this is predictable.

We know which switch goes to which light bulb,

but what if we scramble these wires?

Now the switch for the letter A turns on

the letter C light bulb and the C switch

turns on the B light bulb.

This idea of scrambling the wires,

that's how the Enigma machine works.

Let me show you on the real thing.

The battery is inside in the top right-hand corner

of the machine.

The keyboard has 26 keys.

When you press one of them it connects a circuit

which will then turn on one of these 26 light bulbs.

The light bulbs will then illuminate the letter

that's directly above it on the lamp board.

When you release the key, the circuit

is disconnected and the light bulb turns off.

Each key connects a different path

which means a different light bulb.

Okay, this is the challenging part of the video

understanding the circuit or the path

that the electricity follows throughout the Enigma machine.

Maybe pause the video, get your degree

in electrical engineering and then let's do this.

The three main parts that we need to understand

are the rotors, the keyboard mechanism, and the plugboard.

Let's start up here with the rotors.

This machine has three of them.

This is where the letters get scrambled.

Let's take a look at one of the rotors.

You have the numbers one through 26 for all the letters.

So one is for A, two is for B, three is for C

and all the way around until 26 for Z.

On the side you'll see 26 metal contact points.

There are also 26 on the other side too.

When you put two of these rotors together

the metal contacts connect, making it possible

for electricity to pass through.

On the inside of these three rotors

you'll find lots of wires that connects the two sides,

but as you can see, it's all scrambled.

So let's go through the pin for the number one.

Follow the wire through and it comes out the pin

for the number four.

So in this case an A was changed to a D.

When electricity travels through one rotor

it changes the letter once.

But remember, we have three of these rotors

and they each have different wirings on the inside.

When electricity travels through all three of them

it changes the letter three times.

Then at the end, we have the reflector.

This also has 26 metal contacts.

Inside is more wiring that connects the letters in pairs.

So it goes in as one letter and then comes out

as another letter.

To the right of here is the input wheel.

It has 26 wires that go in and connects

to the 26 metal contacts.

Let's put this all together.

Electricity flows through one of the 26 wires,

let's say the wire for the letter Y.

Then it gets changed to a different letter

at all three rotors.

Then it hits the reflector, which again, changes the letter.

And then it goes back through the rotors again

which changes the letter three more times.

And it comes back out on a wire that represents

a completely different letter.

And if you were counting, this means the letter

was changed seven times.

Now, this is just an example of how the letters

could get scrambled, but the path can and will change.

Each of these three rotors can rotate

to 26 different positions.

When any one of the rotors changes positions

this will also change the path of electricity

making it very difficult to predict which letters

are going to come out.

The 26 wires from the input will travel down the right side

of the machine to the plugboard in the very front.

Now the plugboard was yet another way

that the letters could be around specifically,

you could swap two letters.

So let's say we wanna switch the W and the J.

You could take one of these cables here

with plugs at each end and put one of them into the W spot

and the other one in the J spot.

On the back side of the plugboard,

you can see the individual wires going

to the tops of each socket, and then out to the bottom

of each socket.

Let's take a closer look.

This is the plugboard socket for the letter O.

If nothing is plugged into it the electricity flows in

through the top, then through the shorting bar

and then out through the bottom.

This means that the plugboard didn't change the letter.

It came in as the letter O and then it came out

as the letter O.

When a plug is inserted, it pushes up the shorting bar

so it doesn't connect anymore.

Now the electricity flows in through the top,

out through the top pin of the plug,

then through the cable and out through the bottom.

On the other side.

What came in as an O now it comes out as an E.

Often times, they would use up to 10 of these cables.

Notice how a few of these letters are still left

without a plug.

Let's take a look at the keyboard mechanism.

Each of these keys is connected to a long stem beneath it.

They have springs that push them back up

when you release the key.

the last row of keys have the springs connected at the top.

Right next to all of these keys

most of the space is taken up.

These are the 26 key switches.

These switches are a little bit more complex

than just the on-off switches that we saw earlier.

Let's take a look at just one of the switches.

This one is for the letter P.

The switch has three different copper colored tabs.

The wires are connected back here,

and the flow of electricity is controlled

from the other end.

When a key is pressed it comes down

and hits the rubber end of the middle tab.

What this does is changes where the electricity can flow.

Before a key is pressed the top two tabs are connected,

and after the key is pressed, the bottom

two tabs are connected.

There are 26 key switches and here's all the wires

that are connected to them.

The top tabs are connected to the light bulbs.

The wires go to the left and up to the corresponding

26 light bulbs.

The middle tabs connect to the plugboard.

They go through the wires to the right side of the machine

and down to the corresponding letters on the plugboard.

A wire from the battery goes directly

into the bottom tabs of each key switch.

So each switch has three different tabs

and three different places where they are connected to.

Before a key is pressed the bottom tab

isn't connected to anything so the electricity

has nowhere to go.

This is true for all 26 key switches.

No circuit, which means all the light bulbs are off.

Now let's say we press the X key.

The battery and the plugboard are now connected.

This completes a circuit but it's not as simple

as this circuit we saw earlier.

Let me show you a quick overview of the path of electricity.

Don't worry if you can't keep up quite yet,

we're gonna go over each part one by one.

(mellow music)

Let's take a closer look at each step.

Electricity flows from the battery to the bottom

and then middle tab on the switch for the letter X.

Then it goes directly to the plugboard.

And in this case there's nothing plugged in

for the letter X so it comes back out as the letter X,

up the side and into the input wheel.

Then through three rotors, the reflector,

and then back through the rotors again,

changing letters at each step of the way.

What started as the letter X is now the letter K.

Now we come back to the plugboard for the second time.

The letter K is swapped with a C.

So in through the letter K, through the cord,

and then out for the letter C.

Then travels from the plugboard back

to the middle tab on the letter C key switch.

Remember we started as the letter X

but then came back in as the letter C.

Then it goes out the wire of the top tab

and up to the letter C light bulb.

Then the current flows through the metal light bulb plate

to this tiny wire which connects back to the battery.

This completes our circuit.

As soon as the key is released no more circuit

and the light bulb turns off.

So just to recap, once a key is pressed

electricity goes from the battery

to whichever key switch was pressed.

Then the plugboard, rotors, then back to the plugboard,

then the key switch for our new scrambled letter,

then the corresponding light bulb

and then back to the battery.

The letter has changed seven times at the rotors,

and then possibly two more times at the plugboard.

Remember that the letter isn't always changed

when it goes to the plugboard.

Okay, the electric circuit was the hard part of the video.

If you made it this far, we're doing good,

but there's a little bit more that I wanna show you.

Each time a key is pressed you'll notice that at least one

of these three rotors will turn.

Press a key rotor turns, press a key rotor turns.

This means that if you press a key twice

you'll get two different letters.

In fact, if you keep pressing the same letter

a different light turns on every time.

This is what made Enigma so powerful.

The code was always changing so it was hard to predict

which letters were going to come out.

The way these rotor spin is completely mechanical.

No electricity needed for this.

Even if the battery was taken out,

pressing one of these keys would still turn the rotor.

On the bottom of the machine is a large metal plate

called the actuator bar.

It works like a seesaw or a teeter-totter.

Pressing any of the keys pushes it down on this side,

which pushes it up on the other side.

Around the backside is where the magic happens.

This uses a ratchet and pawl mechanism.

This is the ratchet gear.

And this small piece is the pawl.

When the pawl is pushed up it spins the rotor

and then comes back down.

You can see how this would spin it in only one direction.

This up and down motion will keep spinning the rotors

one slot each time.

The next two rotors work a little different.

Let's take a look at the second one.

Most of the time the pawl can't make contact

with the ratchet gear teeth.

It's blocked by an edge around here on the first rotor.

The first rotor has a tiny notch around the side here.

When the rotor spins the notch travels around the edge.

Watch what happens when it comes up again

on the other side.

The pawl will fit right into the notch

and the second rotor is allowed to spin, but just once.

The next time it will be blocked again

and only the first rotor is allowed to spin.

That edge on the first rotor has to go all the way

around before the second rotor is allowed to spin again.

This will happen once every 26 key presses.

The same thing with the third rotor.

There's another edge on the second rotor

that has to go all the way around

before the third one is allowed to spin.

Last but not least we have the three levers

on the very back with index wheels at the very end.

They ride along the outside of the rotor gear teeth.

This means that the rotors always stop spinning

at the next number.

This is important so that the electrical contacts

always line up between the rotors.

Before you use the Enigma machine,

it would need to be configured with the right settings.

There are four of these settings to go through.

First is the rotor order.

Each Enigma machine came with a set of five rotors.

Choose three of them and then choose which order

to put them in.

Then there's the ring setting for each rotor

which is basically the shifting of these number wheels

but that also includes the notch on the side.

This means this will change when the leftmost rotors

can be advanced to the next number.

Then there's the starting position for each rotor.

You can set this to the tiny windows up here.

And the final setting is the configuration

of the plugboard at the very front.

So everyone in the German army had these settings

in advance.

They were distributed out by paper

so they would know which settings to use

on which day of the month.

Even if the opposing side has their own Enigma machine,

they won't be able to read the messages

unless they know the settings that were in use that day.

Some of the ideas behind the Enigma machine

are complex and sometimes difficult to understand.

However, it may come easier to those

that increase their ability to do math and science.

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(mellow music)