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How did the Enigma Machine work? — Transcript

by Jared Owen · 3,291 words · 425 segments · language en · Watch on YouTube

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0:01- [Jared] This is the Enigma machine.
0:03It looks like a typewriter but it has
0:05a very different purpose.
0:07During World War II it was used to keep messages secret
0:09or in other words encrypted.
0:12In this video, we'll look at why the Enigma machine exists,
0:17how it was used and then we'll take a look at the inside
0:19to see how the mechanism works.
0:22(electricity buzzes)
0:28This video is sponsored by Brilliant,
0:30a fun and interactive way to learn math and science.
0:33Towards the end of this video
0:34we'll take a closer look at their website and app.
0:39While making this video I had a lot of help
0:41from enigmamuseum.com.
0:43These guys took a part in actual enigma machine
0:45and showed me what's on the inside,
0:47behind the panels, all the inside wiring
0:50and how each mechanical piece works.
0:53This would have taken a lot longer to 3D model
0:55and animate without their help.
0:57So big thanks to enigmamuseum.com
0:59and now let's get to some animation.
1:02To really understand the Enigma machine
1:03we need to understand something called encryption.
1:06Let's use an example.
1:08Say we have two friends, Alice and Bob.
1:11Alice wants to send a message to Bob
1:13however, Alice doesn't want anyone else
1:15to be able to read this message such as Eve.
1:18Just as an example we'll keep the message really simple.
1:21Alice will need to scramble the contents of the message.
1:24This is called encryption.
1:27It looks like a bunch of random letters
1:29and if Eve gets a hold of it then she won't be able
1:31to understand it.
1:33When the message gets to Bob he needs
1:35to unscramble the message.
1:36This is called decryption.
1:38Now he can read the original message.
1:40Alice and Bob need to agree on a way
1:42to encrypt and decrypt their messages.
1:45A real simple way to do this is called a Caesar cipher.
1:48This involves shifting all the letters in the message
1:52three spaces to the right in the alphabet
1:54so an H becomes a K, an E becomes an H,
1:58an L becomes an O, an L becomes another O,
2:02and an O becomes an R.
2:05Now the message looks like gibberish,
2:07A bunch of random letters.
2:09When Bob gets the message all he has to do
2:11is take each letter and move it back three spaces.
2:15This will give him the original message
2:17so he can read it again.
2:19Now Eve in the middle, as long as she doesn't know
2:21how the messages were encrypted
2:23she won't be able to read any one of them.
2:26During war encryption is extremely important.
2:29Commanding officers need to be able to get messages out
2:32to the troops on the battlefield
2:33but they don't want the enemy to be able
2:35to understand these messages.
2:37Nowadays encryption is performed by computers
2:40but this wasn't always the case.
2:43The Enigma machine was used to encrypt and decrypt messages.
2:47You can think of this as a very sophisticated
2:49letter scrambler.
2:51It was invented in the early 1900s
2:52and then most famously, it was used
2:55by the German military in the 1930s
2:57and throughout World War II.
3:02This is the keyboard with 26 letters.
3:05And this is the lamp board which also has 26 letters
3:09but these letters can light up.
3:11Each time you press a letter on the keyboard,
3:14a letter on the lamp board lights up,
3:16but it will always be a different letter
3:18than the one that was pressed.
3:20There are usually two people involved
3:22when the machine is used, one person to type in the letters
3:24and another person to write down the letters
3:27that appear on the lamp board.
3:29Let's use our example from earlier.
3:31Type in each letter and write down the letters
3:34that appear on the lamp board.
3:36Now we have our encrypted message,
3:38the scrambled letters that nobody can read.
3:40This message is sent usually by radio using morse code.
3:44The person who receives this message also
3:46has their own Enigma machine.
3:48To decrypt the message or unscramble it
3:51they type in the letters on the keyboard
3:52and write down which letters appear
3:54on the lamp board and out comes the original message.
3:57The Enigma machine was used for both
4:00encryption and decryption.
4:03The person sending the message needs a machine
4:05and the person receiving the message
4:07also needs a machine to be able to read it again.
4:11So how does the Enigma machine know which letters
4:13to give you?
4:14Maybe you press an A and outcomes an H.
4:18How does it do that?
4:20Well, part of the answer is electricity.
4:22Let me show you a simple example.
4:25We have a battery, some wires, and then something
4:28that uses electricity in this case, a light bulb.
4:31This is called a circuit.
4:32It's a closed loop for the electricity to flow.
4:35But if there's a break in the wire,
4:37then the light bulb turns off.
4:39If we put a switch in here, now we can easily turn
4:42the light bulb on or off.
4:44There has to be a complete path for the electricity to flow.
4:48Now let's add another path, one more switch,
4:50and a light bulb.
4:51Now we can turn on two different light bulbs
4:54depending on which switch we turn on,
4:56there's a different path through the wires.
4:58We could expand this even more,
5:00more switches and more light bulbs.
5:03Now, this is predictable.
5:05We know which switch goes to which light bulb,
5:08but what if we scramble these wires?
5:11Now the switch for the letter A turns on
5:13the letter C light bulb and the C switch
5:15turns on the B light bulb.
5:18This idea of scrambling the wires,
5:21that's how the Enigma machine works.
5:24Let me show you on the real thing.
5:26The battery is inside in the top right-hand corner
5:29of the machine.
5:31The keyboard has 26 keys.
5:33When you press one of them it connects a circuit
5:36which will then turn on one of these 26 light bulbs.
5:40The light bulbs will then illuminate the letter
5:42that's directly above it on the lamp board.
5:44When you release the key, the circuit
5:46is disconnected and the light bulb turns off.
5:49Each key connects a different path
5:51which means a different light bulb.
5:53Okay, this is the challenging part of the video
5:56understanding the circuit or the path
5:58that the electricity follows throughout the Enigma machine.
6:01Maybe pause the video, get your degree
6:03in electrical engineering and then let's do this.
6:07The three main parts that we need to understand
6:09are the rotors, the keyboard mechanism, and the plugboard.
6:15Let's start up here with the rotors.
6:17This machine has three of them.
6:19This is where the letters get scrambled.
6:22Let's take a look at one of the rotors.
6:24You have the numbers one through 26 for all the letters.
6:28So one is for A, two is for B, three is for C
6:31and all the way around until 26 for Z.
6:36On the side you'll see 26 metal contact points.
6:39There are also 26 on the other side too.
6:44When you put two of these rotors together
6:46the metal contacts connect, making it possible
6:48for electricity to pass through.
6:51On the inside of these three rotors
6:52you'll find lots of wires that connects the two sides,
6:55but as you can see, it's all scrambled.
6:58So let's go through the pin for the number one.
7:01Follow the wire through and it comes out the pin
7:06for the number four.
7:08So in this case an A was changed to a D.
7:11When electricity travels through one rotor
7:14it changes the letter once.
7:15But remember, we have three of these rotors
7:18and they each have different wirings on the inside.
7:21When electricity travels through all three of them
7:24it changes the letter three times.
7:26Then at the end, we have the reflector.
7:30This also has 26 metal contacts.
7:34Inside is more wiring that connects the letters in pairs.
7:38So it goes in as one letter and then comes out
7:41as another letter.
7:44To the right of here is the input wheel.
7:46It has 26 wires that go in and connects
7:49to the 26 metal contacts.
7:53Let's put this all together.
7:54Electricity flows through one of the 26 wires,
7:57let's say the wire for the letter Y.
8:00Then it gets changed to a different letter
8:02at all three rotors.
8:04Then it hits the reflector, which again, changes the letter.
8:07And then it goes back through the rotors again
8:09which changes the letter three more times.
8:12And it comes back out on a wire that represents
8:14a completely different letter.
8:16And if you were counting, this means the letter
8:18was changed seven times.
8:21Now, this is just an example of how the letters
8:24could get scrambled, but the path can and will change.
8:30Each of these three rotors can rotate
8:31to 26 different positions.
8:34When any one of the rotors changes positions
8:35this will also change the path of electricity
8:38making it very difficult to predict which letters
8:41are going to come out.
8:45The 26 wires from the input will travel down the right side
8:48of the machine to the plugboard in the very front.
8:52Now the plugboard was yet another way
8:54that the letters could be around specifically,
8:56you could swap two letters.
8:57So let's say we wanna switch the W and the J.
9:01You could take one of these cables here
9:03with plugs at each end and put one of them into the W spot
9:07and the other one in the J spot.
9:10On the back side of the plugboard,
9:12you can see the individual wires going
9:14to the tops of each socket, and then out to the bottom
9:17of each socket.
9:19Let's take a closer look.
9:20This is the plugboard socket for the letter O.
9:23If nothing is plugged into it the electricity flows in
9:26through the top, then through the shorting bar
9:30and then out through the bottom.
9:32This means that the plugboard didn't change the letter.
9:34It came in as the letter O and then it came out
9:36as the letter O.
9:38When a plug is inserted, it pushes up the shorting bar
9:41so it doesn't connect anymore.
9:43Now the electricity flows in through the top,
9:46out through the top pin of the plug,
9:49then through the cable and out through the bottom.
9:52On the other side.
9:53What came in as an O now it comes out as an E.
9:59Often times, they would use up to 10 of these cables.
10:03Notice how a few of these letters are still left
10:05without a plug.
10:09Let's take a look at the keyboard mechanism.
10:11Each of these keys is connected to a long stem beneath it.
10:15They have springs that push them back up
10:17when you release the key.
10:19the last row of keys have the springs connected at the top.
10:23Right next to all of these keys
10:25most of the space is taken up.
10:27These are the 26 key switches.
10:30These switches are a little bit more complex
10:32than just the on-off switches that we saw earlier.
10:35Let's take a look at just one of the switches.
10:37This one is for the letter P.
10:39The switch has three different copper colored tabs.
10:42The wires are connected back here,
10:45and the flow of electricity is controlled
10:47from the other end.
10:49When a key is pressed it comes down
10:51and hits the rubber end of the middle tab.
10:53What this does is changes where the electricity can flow.
10:57Before a key is pressed the top two tabs are connected,
11:00and after the key is pressed, the bottom
11:03two tabs are connected.
11:06There are 26 key switches and here's all the wires
11:11that are connected to them.
11:13The top tabs are connected to the light bulbs.
11:16The wires go to the left and up to the corresponding
11:1926 light bulbs.
11:24The middle tabs connect to the plugboard.
11:27They go through the wires to the right side of the machine
11:30and down to the corresponding letters on the plugboard.
11:35A wire from the battery goes directly
11:37into the bottom tabs of each key switch.
11:42So each switch has three different tabs
11:44and three different places where they are connected to.
11:49Before a key is pressed the bottom tab
11:51isn't connected to anything so the electricity
11:53has nowhere to go.
11:55This is true for all 26 key switches.
11:59No circuit, which means all the light bulbs are off.
12:03Now let's say we press the X key.
12:07The battery and the plugboard are now connected.
12:09This completes a circuit but it's not as simple
12:12as this circuit we saw earlier.
12:15Let me show you a quick overview of the path of electricity.
12:18Don't worry if you can't keep up quite yet,
12:20we're gonna go over each part one by one.
12:23(mellow music)
12:28Let's take a closer look at each step.
12:31Electricity flows from the battery to the bottom
12:34and then middle tab on the switch for the letter X.
12:38Then it goes directly to the plugboard.
12:42And in this case there's nothing plugged in
12:44for the letter X so it comes back out as the letter X,
12:47up the side and into the input wheel.
12:50Then through three rotors, the reflector,
12:53and then back through the rotors again,
12:55changing letters at each step of the way.
12:58What started as the letter X is now the letter K.
13:03Now we come back to the plugboard for the second time.
13:06The letter K is swapped with a C.
13:10So in through the letter K, through the cord,
13:14and then out for the letter C.
13:17Then travels from the plugboard back
13:19to the middle tab on the letter C key switch.
13:22Remember we started as the letter X
13:25but then came back in as the letter C.
13:29Then it goes out the wire of the top tab
13:31and up to the letter C light bulb.
13:36Then the current flows through the metal light bulb plate
13:39to this tiny wire which connects back to the battery.
13:43This completes our circuit.
13:45As soon as the key is released no more circuit
13:48and the light bulb turns off.
13:50So just to recap, once a key is pressed
13:53electricity goes from the battery
13:55to whichever key switch was pressed.
13:58Then the plugboard, rotors, then back to the plugboard,
14:02then the key switch for our new scrambled letter,
14:05then the corresponding light bulb
14:08and then back to the battery.
14:10The letter has changed seven times at the rotors,
14:14and then possibly two more times at the plugboard.
14:20Remember that the letter isn't always changed
14:23when it goes to the plugboard.
14:28Okay, the electric circuit was the hard part of the video.
14:31If you made it this far, we're doing good,
14:33but there's a little bit more that I wanna show you.
14:38Each time a key is pressed you'll notice that at least one
14:40of these three rotors will turn.
14:43Press a key rotor turns, press a key rotor turns.
14:48This means that if you press a key twice
14:49you'll get two different letters.
14:52In fact, if you keep pressing the same letter
14:55a different light turns on every time.
14:58This is what made Enigma so powerful.
15:00The code was always changing so it was hard to predict
15:02which letters were going to come out.
15:05The way these rotor spin is completely mechanical.
15:07No electricity needed for this.
15:09Even if the battery was taken out,
15:11pressing one of these keys would still turn the rotor.
15:14On the bottom of the machine is a large metal plate
15:17called the actuator bar.
15:19It works like a seesaw or a teeter-totter.
15:23Pressing any of the keys pushes it down on this side,
15:26which pushes it up on the other side.
15:29Around the backside is where the magic happens.
15:34This uses a ratchet and pawl mechanism.
15:38This is the ratchet gear.
15:40And this small piece is the pawl.
15:43When the pawl is pushed up it spins the rotor
15:46and then comes back down.
15:48You can see how this would spin it in only one direction.
15:51This up and down motion will keep spinning the rotors
15:54one slot each time.
15:56The next two rotors work a little different.
15:58Let's take a look at the second one.
16:00Most of the time the pawl can't make contact
16:02with the ratchet gear teeth.
16:04It's blocked by an edge around here on the first rotor.
16:07The first rotor has a tiny notch around the side here.
16:12When the rotor spins the notch travels around the edge.
16:15Watch what happens when it comes up again
16:17on the other side.
16:19The pawl will fit right into the notch
16:21and the second rotor is allowed to spin, but just once.
16:24The next time it will be blocked again
16:26and only the first rotor is allowed to spin.
16:29That edge on the first rotor has to go all the way
16:32around before the second rotor is allowed to spin again.
16:35This will happen once every 26 key presses.
16:38The same thing with the third rotor.
16:40There's another edge on the second rotor
16:42that has to go all the way around
16:43before the third one is allowed to spin.
16:46Last but not least we have the three levers
16:50on the very back with index wheels at the very end.
16:54They ride along the outside of the rotor gear teeth.
16:57This means that the rotors always stop spinning
16:59at the next number.
17:00This is important so that the electrical contacts
17:02always line up between the rotors.
17:07Before you use the Enigma machine,
17:09it would need to be configured with the right settings.
17:12There are four of these settings to go through.
17:16First is the rotor order.
17:18Each Enigma machine came with a set of five rotors.
17:21Choose three of them and then choose which order
17:25to put them in.
17:27Then there's the ring setting for each rotor
17:29which is basically the shifting of these number wheels
17:32but that also includes the notch on the side.
17:37This means this will change when the leftmost rotors
17:40can be advanced to the next number.
17:42Then there's the starting position for each rotor.
17:45You can set this to the tiny windows up here.
17:50And the final setting is the configuration
17:52of the plugboard at the very front.
17:56So everyone in the German army had these settings
17:59in advance.
18:00They were distributed out by paper
18:01so they would know which settings to use
18:03on which day of the month.
18:05Even if the opposing side has their own Enigma machine,
18:08they won't be able to read the messages
18:10unless they know the settings that were in use that day.
18:14Some of the ideas behind the Enigma machine
18:16are complex and sometimes difficult to understand.
18:19However, it may come easier to those
18:21that increase their ability to do math and science.
18:25brilliant.org is a problem solving website
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18:30science and computer science.
18:33The idea here is to learn by doing.
18:35They teach you a concept and then immediately you get to try
18:38it out in a fun and engaging way.
18:41You can use Brilliant to help you as a student in school
18:43or as a professional or anyone who wants
18:46to keep their skills sharp.
18:48There's a wide range of content
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18:52Instead of just learning a formula and blindly plugging
18:55in the numbers, you get to visually see why
18:57that formula works.
18:59There's nothing quite so satisfying
19:01as when that light bulb goes off in your brain.
19:04I like Brilliant because it shows
19:05that learning can and should be fun.
19:08You can sign up for free by going
19:09to brilliant.org/jaredowen.
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19:16(mellow music)

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