The Two Generals’ Problem

  • нийтэлсэн 3 сарын өмнө

    Tom Scott

    Үргэлжлэх хугацаа: 8:26

    Time to tell a story about idempotency, computer science, and the Night of the Multiple Orders. • Sponsored by Dashlane -try 30 days for free at: www.dashlane.com/tomscott
    MORE BASICS: mnclip.info/playlist/PL96C35uN7xGLLeET0dOWaKHkAlPsrkcha
    Written by Sean M Elliott and Tom Scott
    Directed by Tomek
    Graphics by Mooviemakers www.mooviemakers.co.uk/
    Audio mix by Haerther Productions haerther.net/
    Thanks to Dashlane for sponsoring the video! If you're techie enough to watch this video, you should be using a password manager. Get a 30-day free trial at dashlane.com/tomscott
    I'm at tomscott.com
    on Twitter at tomscott
    on Facebook at tomscott
    and on Instagram as tomscottgo

Tom Scott
Tom Scott

Yes, I had help with the graphics for this series. There's no way I'd have animated that myself! On that note, thanks to Dashlane for sponsoring and helping me hire an animator: their free trial link is https://www.dashlane.com/tomscott

4 сарын өмнө
Akin Turhan
Akin Turhan

I have thought about dashlane I want to know the advantage over Google chrome random password generator and manager that is synced with one master password. they don't know any of the passwords either.

Сарын өмнө
The Superginge
The Superginge

As glad as I am that you're getting sponsored, I feel I should tell people that Firefox is starting to offer this password security option for free, though before anyone gets angry at me, I don't know what level of security it is, comparatively, I just want to make people aware of options!

Сарын өмнө
Matti Lüdke
Matti Lüdke

Why not send a person from each army to the middle of the valley. Then both discuss a time and go back to their army. That way they will know if the message was received by the other army. As the Danger of the route lies in the middle of the valley they will get back safely.

2 сарын өмнө
صالح
صالح

Hey there is a way to solve the 2 genrals problem and it's a horne or war drums because they are loud enugh to hear

2 сарын өмнө
Dark Thoughts
Dark Thoughts

Now you know the issues protocol standards committees have to 'foresee' when designing a communication protocol.

3 сарын өмнө
Federico Olivares
Federico Olivares

To me is simple the general's problem A sends "is 8pm ok? Send "ok" back for yes, if you dont receive an ok back from me, send "response?" Back 2 more times. If you dont get an ok from me, consider it null. I too will send a 2 "response?" If i dont listen back So gen B agrees, Sends one Ok gets Ok back Both attack. Gen b sends ok doesnt hear back, received "response?" Sends ok Receives ok both attack Gen b sends ok doesnt hear back, doesnt receive response at all. Asumes A's ok has been intercepted as they would have sent one or more "response?" Back otherwise. Sends "response?" And so on. If all 5 messagers get caught after the initisl messsge, the attsck wouldnt go through. If just 2 Oks do go through, the attsck goes through

4 цагийн өмнө
Phillip Otey
Phillip Otey

I mean you need 2 minimum. A keeps sending troops saying: send one troop telling us what time to attack. We will keep sending troops until the package is received, and if the time of attack has not past we are a go.

8 цагийн өмнө
Ady Day
Ady Day

Don’t rely on technology too much..nothing is built to last!

9 цагийн өмнө
Name
Name

Just make an agreement that 2 or more acknowledgements means you can attack

2 өдрийн өмнө
Jo 1337
Jo 1337

It's 2 am and I regret nothing

3 өдрийн өмнө
Vysair
Vysair

Or maybe both general could send dozen more message until it hit certain threshold and that will confirm it.

6 өдрийн өмнө
10k12
10k12

2:35 why not let them meet in the middle, so if they perish, they perish together and no message is received, but if they manage to meet, they can return and there are no threats on the way back to the generals.

7 өдрийн өмнө
Shaurya Pant
Shaurya Pant

Well, after both the teams have received confirmation of the other party that they know that you know and will go at 8PM, I don't see any further need of sending messengers. Can someone explain, please?

8 өдрийн өмнө
Andre L
Andre L

How come this problem exists at all, if the proposed time is 8 pm, and both of them acknowledged the acknowledgments, then why would A and B need to keep sending acknowledgments? They both acknowledged the proposal and acknowledgment, so it's already planned? They both already know that it made it to the other side at least twice, so what's the problem? This just feels like it's not really a problem.... How is this line of reasoning incorrect?

8 өдрийн өмнө
Markus B
Markus B

I should be asleep but general B didn’t give me a confirmation

8 өдрийн өмнө
john wick
john wick

Simply. General A sends a messenger which returns after delivery of the message. If the messenger does not return after a suitable time span. It is safe to assume something happend and another messenger needs to be sent

8 өдрийн өмнө
Space Griffin
Space Griffin

but wouldn't a and b know they've received the message by the third message?

9 өдрийн өмнө
DukeOfEarle88
DukeOfEarle88

£7.74 word.

10 өдрийн өмнө
UberKrassMann
UberKrassMann

2:55 starts sweating.....

10 өдрийн өмнө
Skepty
Skepty

Just tell them to make a fire signal after they do, as confirmation. Not that hard.

11 өдрийн өмнө
Ashor
Ashor

for the two generals, couldnt one side send a messenger with the message telling them to attack at a certain time (sundown) but to ensure they both know they both have to shoot a cannon ball to the west of the other general at sunrise) if they both observe the cannon ball west of them then they know they will attack at sundown

11 өдрийн өмнө
Midhunraj R Pillai
Midhunraj R Pillai

I wonder how the generals problem is unsolvable. Please correct me whats the mistake of the solution below, Step1: General A sends message saying attack at 6pm (Here, A establishes the time) Step 2: General B gets the message, sends back an acknowledgement 1 for the message 'we go the time' (B gets the time) Step 3: General A gets the ACK 1 (now, A knows that B got the time of attack. But B won't attack because B don't know that ACK 1 is reached at A. so..) A sends a confirmation ACK 2 back Step 4: General B gets the ACK 2 (now, B knows that both A and B establishes the time. Also B got the ACK 2, meaning B knows that ACK 1 reached A. But B knows that A won't attack until A confirm that B got the ACK 2. so...) B sends a confirmation ACK 3 back Ahhhh this trend continues and no one will attack since they cannot make sure that the previous ACK sent by them is reached at the other end!!! I am sorry (T_T)

11 өдрийн өмнө
Ivan farlenkov
Ivan farlenkov

Have generals send messagers at set periods of time even when there is nothing to send. If there is no messager, ask about it in the next message.

12 өдрийн өмнө
Gareth H
Gareth H

@Ivan farlenkov You really do not get it. Oh well, nevermind. Stick to flipping burgers.

11 өдрийн өмнө
Ivan farlenkov
Ivan farlenkov

@Gareth H Why not? If messagee is lost, request to resend will be eventualy get to the other side.

12 өдрийн өмнө
Gareth H
Gareth H

That is the ping approximation that is used. But it is not a solution to the problem, there is no solution.

12 өдрийн өмнө
Monsieur P.
Monsieur P.

My bank card would’ve texted me to confirm charge after being pinged to debit my account identical amount of money. It’s kind of stupid that nobody selling the food didn’t notice.

13 өдрийн өмнө
Monsieur P.
Monsieur P.

😂 these damn apps!

13 өдрийн өмнө
novicetheaf
novicetheaf

This is a classic lack of dev testing prior to sending it for testing prior to deploying it to the end user, and QA testing.

13 өдрийн өмнө
Kevi Kiru
Kevi Kiru

Even your paid promotions are interesting to listen to!

14 өдрийн өмнө
Oasia
Oasia

Why dont the say just to fire a cannon if they recieve the message

14 өдрийн өмнө
Julian Danzer
Julian Danzer

2:57 umm...

14 өдрийн өмнө
Floofzy Kitty
Floofzy Kitty

1:38 What are you talking about? Of course they made it to the other side. Just not the side they intended.

15 өдрийн өмнө
Muhammad Adam
Muhammad Adam

Surely after the 4 messengers they wouldn't need confirmation any further confirmation because both would have already known that it's agreed upon

19 өдрийн өмнө
Terrain
Terrain

You didn’t solve the two generals problem, you solved another problem created by it being unsolvable, which arguably is more dangerous than the two generals problem

19 өдрийн өмнө
BeforeReform
BeforeReform

per your ad... there is *always* the possibility of brute force getting through. It could take years, or decades on average, but there is always a chance someone gets lucky.

20 өдрийн өмнө
Angelmarauder
Angelmarauder

TCP/IP

20 өдрийн өмнө
its_a_trab
its_a_trab

You could just send the original guy back.

21 өдрийн өмнө
Emerald Block Boat
Emerald Block Boat

I'd say that if B received two verifications then do it

21 өдрийн өмнө
TARINunit9
TARINunit9

Proposition for the two generals problem: instead of sending one messenger, send a pair of messengers. One messenger stays at camp B and the other returns to camp A. If no messengers return to camp A, then it's obvious that the message was intercepted on one of the two trips, so you send another pair

22 өдрийн өмнө
Lloyd Thorpe
Lloyd Thorpe

What they should have done is just starve the castle out like they most commonly did

25 өдрийн өмнө
The Nintendo Fan
The Nintendo Fan

Honestly, the red army would automatically assume the blue army got the message and would attack on that time

25 өдрийн өмнө
Eric ON
Eric ON

Atleast once invocation solves this issue as well. I.e. let the client keep spamming the same request until one confirm has been recieved.

25 өдрийн өмнө
Emil Sørensen
Emil Sørensen

I'd definitely not like having a master password that, if lost, renders my entire online life unrecoverable. How can you possibly make your one password unforgettable? Chisel it into an immovable rock?

26 өдрийн өмнө
LED Kat
LED Kat

Send the entire army as the messenger

27 өдрийн өмнө
Beowulf Macbethson
Beowulf Macbethson

I was watching a video about Morgoth from Lord of the Rings, why am I here. Also your video is great and informative.

27 өдрийн өмнө
TIMΞ СнΛИGΣ
TIMΞ СнΛИGΣ

But the generals would know after a few acknowledgements? What am I missing here

28 өдрийн өмнө

Дараах

Why Electronic Voting Is Still A Bad Idea

12:01

Why Electronic Voting Is Still A Bad Idea

Tom Scott

Үзсэн тоо 317

There is No Algorithm for Truth - with Tom Scott

59:35

There is No Algorithm for Truth - with Tom Scott

The Royal Institution

Үзсэн тоо 468

Ghostbusters Afterlife Trailer REACTION

5:53

Ghostbusters Afterlife Trailer REACTION

Beyond The Trailer

Үзсэн тоо 99мянга.

FINALLY Buying Land.. Step 1 to BUILDING OUR DREAM HOME | VLOGMAS DAY 8

21:01

MADISON IS PREGNANT!!! HERE WE GO AGAIN!

11:41

MADISON IS PREGNANT!!! HERE WE GO AGAIN!

Kyler and Mad

Үзсэн тоо 977мянга.

This Video Is Sponsored By ███ VPN

7:26

This Video Is Sponsored By ███ VPN

Tom Scott

Үзсэн тоо 1

I'm Not A Robot ✅

7:40

I'm Not A Robot ✅

Tom Scott

Үзсэн тоо 988

The Language Sounds That Could Exist, But Don't

6:31

G-Force, Jerk, and Passing Out In A Centrifuge

4:49

The Image That Can Break Your Brain

1:43

The Image That Can Break Your Brain

Tom Scott

Үзсэн тоо 4

Why You Can't Trust Me

9:38

Why You Can't Trust Me

Tom Scott

Үзсэн тоо 1

So You've Learned To Teleport

3:54

So You've Learned To Teleport

Tom Scott

Үзсэн тоо 1

Can The Words You Read Change Your Behavior?

4:37

Can The Words You Read Change Your Behavior?

Tom Scott

Үзсэн тоо 387

Will YouTube Ever Run Out Of Video IDs?

5:10

Will YouTube Ever Run Out Of Video IDs?

Tom Scott

Үзсэн тоо 2

Do The Numbers On Toaster Dials Mean Minutes?

2:13

The Bielefeld Conspiracy

2:21

The Bielefeld Conspiracy

Tom Scott

Үзсэн тоо 998

Gordon Ramsay's Ultimate Budget Food Guide | Ultimate Cookery Course

22:40

Traveling Cross Country Living In Our Tiny Home Van

38:42

Traveling Cross Country Living In Our Tiny Home Van

Dolan Twins

Үзсэн тоо 856мянга.

YouTube Rewind 2019: The Musical

9:41

YouTube Rewind 2019: The Musical

Michelle Khare

Үзсэн тоо 987мянга.

Harry Styles - Adore You (Live on The Graham Norton Show)

3:51

Harry Styles - Adore You (Live on The Graham Norton Show)

HarryStylesVEVO

Үзсэн тоо 1,2сая

Billie Eilish - xanny

4:26

Billie Eilish - xanny

BillieEilishVEVO

Үзсэн тоо 22сая

South Africa’s Zozibini Tunzi is Miss Universe 2019 | Miss Universe 2019

2:31