When guys like these become professors, they end up making a generation of youngsters who revolutionise the technology.

Could you also talk about garlic routing? Which is more vulnerable to leeks?

"No one really knows anything about what's going on at all." Great description of my life.

As someone currently going for their masters in cybersecurity. They have been a massive help in understanding comp sci and IT concepts. While my professors are great people and they mean the best its was easier for me to get a concept down with a 10-30min computerphile video than a 4 hour long lecture with no practical application. Just wanted to say thanks chaps you been a massive help.

I wish he was my teacher when I first took up computer science.

That preview picture tho. At first blink I was sure that was anything but an onion lol

Confidentiality is hiding the message, anonymity is hiding the sender.

Using Tor to access Facebook... Oh what irony...

When someone else goes "TOR router" and you're there like "The Onion Router router?"

The absolute best explanation of onion routing ever heard.

Traffic Analysis (discussed from about 11:20 to 13:00) is one of the major reasons tor works best when a lot of people near you are also connecting to the network. The more people that are connected to the same node, the "noisier" it is on the harder it is to correlate the inputs and outputs. Of course, this resistance to analysis is at a cost: all of that extra traffic also has to be processed by the node at some point, making it slower, so it's a bit of a balancing act

This is definitely my favorite guy on this channel.

I love that people are always trying to charge money for computer courses and that, whereas the best teachers on youtube do it for free. I have so much respect for Mike and Tom. Keep doing what you are a doing and set up a Patreon because the information you are teaching on this channel is amazing and I would gladly donate what I can to you guys.

I love Dr. Pound's in-depth explanations, and this channel, too.

4:06 Layer encryption. 6:02 Attack. 7:42 Onion routing. 8:08 Speed. 9:24 Eavesdropping. 10:28 Drawbacks. 13:03 Cells.

Been following for years and I love the content. Always so fascinating. One of the best channels on YT.

A key point left out: Network requests can often have blatant identifiers of who sent that request, and the specifics about what they're doing. It's not just always seemingly arbitrary requests that give no hint of who issued the request. Like when using any sort of system you have to user a user ID or password for. This means the final node on the routing path actually can figure out info about who originated the request, and possibly why, despite having the multiple levels of encryption and routing between themselves and the originator

Clearest description of Tor I've ever heard, obviously a teacher!

ogres have layers

I enjoy listening to Dr. Pound's explanations. I can understand him. The subject is fascinating.

Uh I think you'll find that TOR actually stands for The Ogre Router, because ogres have layers, like cakes.

Great insight for a newcomer to the topic, thank you for taking the time to explain!

Discovering this channel with this nice topic : thanks a lot! Short question, Mike Pound evokes the weakness of finding timely correlations between entry and exit points. But, could some kind of controlled shuffling of the various requests do the trick ( a mixing with other requests)?

few questions: 1- why not asymmetric encryption as opposed to symmetric? 2- could you make it harder to de-anomynise you if packets had a short, random delay before being sent to the next node? 3- could you make it harder to de-anomynise you if you added dummy data or dummy packets at the entry and/or exit points?

I love the Computerphile episodes that Mike pound is in!

Great vid, I really appreciate this content. Does anyone know how long a routing chain lasts? It seems pretty important that the paths you take don't remain constant. Would a new route be established with every request, browsing session, or change in server destination? Or is it more of a timed switch?

I knew nothing about Tor but I saw it was a Mike Pound video so I watched it, definitely glad I did and I feel like I learned something new and important from it :) Thanks a lot for the videos!

I often find great content videos on this channel ! Guys are technically very rich and great in explaining things easiest way possible - Top man !

Can make a video by explaining how i2p works ?

I love your videos, they are very interesting. Can we make slow loris attacks anonymously using TOR ? If so, there is still potentially the problem of comparing signals tempo ?

So I created a chain proxy a few years back I could easy implement encryption into the request but man that part about checking the hash at the end to determine where the packet should go is Genius !

When we're talking about digging into the 'tempo' of messages and de-anonymizing the data- what is the certainty that we're able to establish on those? Correct me if I'm wrong but there should be a significant amount of variation resulting from using a lot of nodes, and obviously, the more nodes we use, the more varied our output 'tempo' is going to be. So we have two variables there- the size of the message (which stays the same) and the time interval it takes for the message to arrive at the last link (point B in the video) which is varying depending on many external factors. Also, wouldn't the data be sent over different amount of nodes (and different nodes) every time, which would add to the ambiguity? Great video by the way, thanks for making those!

The last minute of the video contains one of its most important points.

this guy and the animations are amazing!!

Oh man these are my favorite. Thanks Dr. Pound!

I could listen to this guy explain stuff all day...

I love these videos!

5:16 what an enthusiastic server

This man is my favorite on this channel I wish he was my personal teacher things would be much simpler.

Great videos! Very informative and well explained. Any chance you would make a similar video for I2P?

Interesting video! But I'd like to know how the key exchange works between tor nodes

Great video but I am not sure about the last part. An Etherframe is 64-1518 bytes long, not 1512. 1512 would only include the data in the frame, and source mac and destination mac. The data encapulated by the fame is set to a default maximum transmission unit of 1500. This does not include the Preamble + Start Frame Delimiter ether type FCS or the inter frame gap. I am also not sure about the point that was made about how a router decides to forward a packet. The router would check the destination mac address to see if it is being sent to its self. Then the router would check the CRC hash at the tail of the L2PDU to see if there was corruption to the transmission of the packet first to determine if it is even going to process the frame. Then it would check the destination ip address and figure out it if will need to do a routing table lookup or if it is destined to the router its self. A new hash is created each time the ethernet frame is rewritten, which is each time it hits a layer 3 device that needs to route it. The hash must match each time a switch or router checks the CRC, if it does not pass it will drop the frame or packet. The tor protocol does encryption at Layer 6 of the OSI model and would not interfere with the passing of the CRC. As you said at 13:14 a router determines if a router needs to read a message or forward based on the hash. Incorrect because if the hash does not pass it will drop the packet. A router will determine whether or not to forward the packet based on its IP destination in the L3PDU, not the CRC hash. Does tor networking handle routing differently where something would need to be done in the application layer?

This video made my day ! I got to learn a valuable lesson about Tor. Thankyou!

Super interesting subject and well explained. Thank you.

Why are the lines on Dr. Pound's illustration torn?! Like some sort of screen tearing. It seems to be with almost all the lines drawn. It's really tearing me apart...

Very interesting stuff... another extra reason for the idea that the more people use TOR, the safer it is. Then again, the most congested it might become. I imagine a potential solution for traffic shape analysis would be for client and end node to have constant input without spikes with complete saturation, filling blanks with garbage. But that would also make the whole thing kinda useless in terms of speed.. or extremely complicated to pull. :P And also extremely taxing for every node.

i love when mike explains things

Best computerphile video I have seen yet.

Great video!

This guy definitely put all of his skill points into speech.

Thanks. I don't know why but I find the way Dr Mike Pound talks about subjects to be very engaging. The pace, content and level is exactly at the level I like 'Great Job!' As the Americans would say. As a Brit it's more of a 'he's OK to be fair, end of' (great job, ignore the brit thing)

Very cool guy. Its always nice to hear a lection from him. Next video could be how do people find you on a tor via flash or ads or cookies and so on.

I wish Mike would have discussed the differences between exiting the TOR network into the clearnet and accessing hidden services (the packets never exit the TOR network).

12:00 He talked about the possibility of de-anonymization through message time signature analysis. Isn't there way to, sort of, stagger those time signatures somehow?

I totally didn't see something different on the thumbnail at first glance.

great easy to understand explanation as always

Such a bad choice of an onion drawing, cant stop seeing it. Love the channel!

Great video, but I think you should probably have mentioned hidden services (or otherwise servers running nodes themselves, such that the B node is the same as the server you're communicating with). Combining that with information about running one's own node (such that the user controls node A) gives a more complete picture of optimal Onion Routing conditions (though, again, not entirely without potential for pattern analysis). Lastly, I think some people in the comments appear to be treating "being an exit node" like a thing one chooses, so this is just to say that a node is a node and routes, while they can be controlled manually by the sender, generally are generated and the exit node has nothing to do with choosing which node will be the exit (or entrance, for that matter). Love your work, keep it up!

So do they do things like delay the packets by some random amount for each packet to make the tempo random, or to buffer them so that it waits for a quarter second collecting packets and then evenly distributes them in a random over the next quarter second, or to add random nonsense packets in at every point to make it more difficult to count packets?

Nice explanation..But one question I have, I am doing reverse engineering on TOR network traffic. Can we distinguish between a relay node (B,C) and actual sender (A). Sender may be a relay node. Any byte pattern for this? Or any logic on the basis of RX and TX?

I would not want to be the last guy forwarding a request to some dodgy website.

We gonna have a word about the video thumbnail

Wonderful intermediate overview. Would recommend.

Simply amazing! This is exactly how you should explain technology. Thank you.

wouldn't a downside to being a node be that you'd get into trouble for the sites that other people went to? because it'll look like your computer went to those sites when it was someone on the other side of the world who actually requested it

Why not add random delays to solve the deanonymizing problem? Would it be too costly for servers and make the connection too slow?

best host ever I absolutely love him doesn't matter what he is talking about its always interesting. .

Excellent video, as always. Thanks a lot!

Hey great video. You talk a lot about the key excange. But how does this work? Cant the Routers see your IP when you pass them the key directly? Or if you send it trought the Routers you've already connected with, cant the see the Key for the next Router?

I always thought tor stood for "the onion ring". mmm... onion rings...

I like this guy. I just subscribed. He explains things well like a friend who wants to teach you.

Any update on TOR over a VPN? Any preference? Thanks for the great video's.

I love these videos, but one day I'll make a compilation of Him putting His shirt straight on His left shoulder (with Yakety sax of course) :-D

Wouldn't it be possible to use random network delay to prevent what you defined as frequency deanonymization? Lets say you have an average delay time on 1 second, and then each message gets randomly delayed from 0 to 2 seconds on each of the nodes. Yes, this would slow down the speed, but would greater improve the anonymity.

I really appreciate your videos man, truly

Bravo. This man is the most gifted, lucid explainer of computer matters whom I have come upon. His diagrams, articulateness, and sense of organization are superior. He is commandingly competent. Two small complaints: (1) he speaks too quickly; the pace of his (British) English would be more suited to a neophyte audience were he to slow down, and (2) his occasional jokes sometimes come at crucial moments and so detract from the clarity. He does employ jargon that sometimes I, at any rate, have to look up, when I can catch it (the speed issue again), but that nay be on me, not him.

Couldnt you theoretically have the messages passed through some random functions on every note so that their sendtime differs in a intervall of 0.1 to 1 second or something? Would that not solve the correlation possability ?

4:25 I can't be the only one who sees something....

If you use a torrent via TOR, then the servers that are feeding you your files will have your IP address. The data stream initiated by your computer will include your IP address, when using a torrent. No one sniffing the hops will know your IP address or what you are doing. But when your request reaches the intended servers, then those servers will have your IP address, if you are transferring a file via a torrent. Not covered in this video is that TOR can be used for all manner of internet activity (not just web browsing). But web browsing is probably the most heavily used part of internet activity, including over TOR. So take note that your web browser can give away your identity. If you do not take steps to keep yourself anonymous, your web browser will send along a load of information about your computer, which the server on the other end will see. Also: To remain anonymous, you must disable javascript when you use your web browser. But doing so will break the functionality of countless web sites. You will find that they do not load properly. Some sites will know that you disabled javascript, and will tell you that their site requires javascript to be enabled for it to work properly. But if you enable javascript, you will almost certainty give up your identity. Lastly, due to bad actors, abusing the fact that TOR keeps them anonymous, countless web sites will not accept connections from TOR exit nodes (those nodes are publicly known). So if you use TOR to go to some web site, it might time-out, or you might get a connection refused message, or something similar. And then there is Windows, that monitors everything that you do, and phones home. If you use TOR on a Windows computer, you really do not know what is being logged on your computer, or being sent to Microsoft. For the safest TOR experience, use the Linux TAILS operating system. If will be a bit of a struggle to surf the web, via TAILS. But that is due to TAILS protecting you from yourself. The roadblocks that TAILS puts up are to keep you from revealing your identity, when you did not realize that you were about to reveal your identity.

Thanks for releasing this just before your exam

How does the client side share k2 and k3 without creating a connection with those machines?

Damn this thumbnail

YES I've been waiting so long for this xD

Would it _help_ throw off correlations between "the two points" by simultaneously talking to several end servers at once? As in, even if you're really just looking at "Facebook", you also send requests to "Google" and "Twitter" at the same time. I know that it'd probably still be possible to pick out some patterns, but would it be a worthwhile precaution?

Gabe from Office seems to have taken a keen interest in tech! Good for Sabre for promoting cross team functions

What are your thoughts on the US government claiming that Tor is essentially useless and they can spy on Tor traffic? Do you believe its entirely based on sniffing the beginning node and end node?

this guy is so interesting to listen to , captivating is the word

So would it be possible to setup a cabinet of exit nodes and harvest urls from the packets, essentially mapping the tor network and making .onion directories easier to find?

8:53 "We've got a situation here where no one really knows anything about what's going on at all" gee sounds like my life and politics and lots of things really

You'll probably need to reupload this. There is a serious flaw at 4:09, where no image of Shrek appears when he says "in layers" and raises his eyebrows.

I think that you can partially solve the problem, with someone controlling A and B (front and exit node) and measuring intervals between front and exit nodes, but you need to sacrifice performance... The idea is that you could delay each message by some random amount. Construct message with variable length of hops between you and server. E.g. exchange some keys from K1,K2,K3,K4,K5, construct 1st message K1->K5->K2->server, 2nd message K3->K2->server, 3rd message K4->K1->K4->K2->server, etc... because no node knows full path, and each message will have different amount of hops, all messages will arrive at different time ;) that's the general idea. In theses cases when server doesn't have "sticky" sessions, you can change exit not for each message!

I got a question about the protocole you present, on its way back, how does K2 know where to send the paquet? it seems to me that there might be multiple clients using a circuit with k2 k3 or K1 and K2; so any message coming from K3 might be destined to not only one user. Is there some kind of information in the message to remember which circuit is being used?

That picture in the thumbnail might not of been the best choice.

3:30 if I as a client negotiated a symmetric key with each of the Tor Nodes that means each Tor node knows my IP address correct?

This video was great! I feel bad this channel doesn't have the same activity that it once had....

I really like your videos. Can u please do one about transducers.

What if the majority of the nodes is controlled by NSA?

If I set up a TOR node, am I responsible for all the traffic that goes through it? Could you be arrested if some of the traffic was illegal?

To keep people from matching up A and B couldn't you just have several machines that are all synced running through the same B node? Because at that point you wouldn't be able to tell which one was the actual person, and which was just the synced machine? Of course for this to work you'd want several synced machines all running at the same time. Though if you had them all set on a randomized timer so when they sent something all of them would send at the same time +- .3 seconds it may be slightly harder to tell. I'm not sure just curious, any thoughts?

Very interesting and explained well. Cheers