Hot answers tagged

8

The circuit: [ Tor user <-> Guard node <-> Middle node <-> Exit node <-> Server ] Sending data to server: The Tor client always encrypt the data for the exit node And then encrypts it again (another layer) for the middle node And then again (yet another layer) for the guard node This way one layer need to be peeled of at each hop in the ...


8

Setting up circuits is very expensive. It involves several round trips, and it involves lots of public/private key operations for the servers. Continually creating new circuits at a high frequency is wasteful and thus quite abusive. Please don't do it.


7

Requesting a NEWNYM over the control port will tell Tor to consider the currently used circuits "dirty" (this normally happens after 10 minutes, with a few exceptions), at this point it will no longer attach new streams (connections) to the "dirty" circuit, and instead will attach them to a "clean" circuit (it doesn't normally build a fresh one at the time, ...


6

Tor puts many streams onto a single circuit. If possible, the same circuit is used for up to 10 minutes -- see For how long does a circuit stay alive? for some details. Accordingly, if you visit a website and it takes a hundred http connections to fetch it all, Tor will use the same circuit for all of that. If you stay on the website for a while and load ...


6

During the time when you encountered this fluctuation Tor had some problems with a botnet. Some ukrainian guy deployed Tor nodes and they build cuircits. As there were quite a huge amount of clients, this put a fair share of load on the relays. Maybe your relay also was affected. This fluctuation should have disappeared because tried to remove the malware.


5

It's complicated. There are many reasons Tor builds circuits preemtively: access hidden services, provide them, exit to any ports that you may want to use (based on recent behavior) and also measuring the network to determine what latency/circuit build times to expect. circuit_predict_and_launch_new() has all the gory details.


5

No. Tor traffic does not necessarily all exit at the same exit node. For each socket connection that the client sets up, a circuit is used that ends in an appropriate exit node. That is an exit node that allows the IP and port the client is trying to reach.


5

Tor often builds circuits well in advance of actually needing them. This speeds up various operations since building circuits are quite expensive and time consuming. Circuits it has build are earmarked for a specific purpose, say making exit connections out of the Tor network. If Tor wants to do some specific operation (say connect to an introduction ...


5

If you are looking to be able choose a specific entry nodes for specific period of time you may open the torrc and insert the following line: EntryNode $fingerprint On restart of Tor it will use the entry nodes if available.


5

Regarding the question "Can you be arrested?", yes, you can be arrested all the time. In most countries you can be arrested for looking funny at a police officer. In most countries you will also be released as soon as they have no reason to suspect you anymore. Interesting questions would be would a prosecutor charge you and would those charges hold up in a ...


5

In Tor Browser, every domain gets it's own circuit. The Design and Implementation of the Tor Browser document has some more details on it. Frankly, you get an own circuit for every domain shown in the address bar. So, if you visit google.com a different circuit is used than when you visit example.com even when content, like an advertisement, is loaded from ...


4

Functions for node selection and circuit construction can be found in routerlist.c and circuitbuild.c files in src/or directory. Possibly the most relevant ones are the following: smartlist_choose_node_by_bandwidth_weights compute_weighted_bandwidths circuit_establish_circuit onion_extend_cpath onion_pick_cpath_exit choose_good_entry_server ...


4

Circuit on-demand are purposely to replace the previous circuit if the relays selected initially are bad, unstable, lower bandwidth/throughput, congestion, attackers relays etc. In addition, if the Tor client uses the same exit node and configured to use the same circuit, then the streams from many websites will passes through the same circuit. Else, in any ...


4

You can download a standalone version of Vidalia if you are on Linux or Windows. For Windows the extension is .exe and for Linux it is .tar.gz for Vidalia. .asc is the signature file to check the integrity of the standalone Vidalia bundle. Then you have to extract the Vidalia bundle to some folder you can write to. It is not recommended to use the folder ...


4

Yes, that's correct. There are two types of circuit handshakes -- the original, called the Tor Authentication Protocol in Ian's paper about it: http://freehaven.net/anonbib/#tap:pet2006 and then the better one, called NTor: https://gitweb.torproject.org/torspec.git/blob/HEAD:/proposals/216-ntor-handshake.txt https://gitweb.torproject.org/tor.git/blob/refs/...


4

so I guess the entry node is limiting the traffic if you make too much traffic, right? No. The long guard rotation period is for security reasons. The more often you pick a new guard, the higher the chances that you will encounter a bad one (i.e. owned/controlled by the party you want to hide from). See also: Changing of the Guards and One Fast Guard ...


4

I think you want to check out the configure option for tor2web mode, which should do pretty much what you want. No special second instance running a tor relay would be necessary


4

Introduction and Rendezvous points are only used for Hidden Services. The Introduction point is chosen by the Hidden Service and published with the HSDir servers handling the Hidden Service. When a user wants to connect to the Hidden Service, they randomly choose a rendezvous server and ask the Hidden Service (through the introduction point) to connect ...


4

Nice timing, we just expanded our tutorials around this! For this you should use new_circuit() and attach_stream() rather than NEWNYM. For an example of doing this see... https://stem.torproject.org/tutorials/to_russia_with_love.html#custom-path-selection


4

Ok, I figured this out. For some reason the custom onion address I made with Shallot was no longer working. I made a new hidden service and got rid of the existing one, restarted Tor, and voila! I'm not sure why this happened, but this solved both hidden services that had stopped working.


4

The type of attack you are describing is a congestion attack. In theory, the simplest form of such an attack would be a general DoS on the Tor network. Taking things one step further, a congestion attack could be used in conjunction with traffic correlation to monitor a given user of the Tor network. Such a strategy is discussed in A Practical Congestion ...


4

Yes, they are taken from the bridge. Every bridge has the latest directory information cached (just like any directory mirror), and Tor clients fetch them directly and build circuits with the bridge as an entry guard. A bridge that has just started for few minutes could cause clients who connect to it fail since directory information has not been downloaded ...


3

Yup, and thank you for running an exit! Netstat, lsof, and other connection resolvers can tell you the number of active connections a process is making. Stem also has a module to make this easy. Tor has a feature to prevent debuggers like gdb from analyzing tor's memory. This feature inadvertently breaks connection resolvers like the above, so you'll need ...


3

Tor network sometimes rejects/avoids nodes that misbehave in some way, e.g. by sending invalid traffic or (in the case of exit nodes) modifying exit traffic, see the badRelays page on the wiki. However, such misbehavior is often caused by misconfiguration or by some other entity (an antivirus program, the node operator's ISP) modifying the traffic that the ...


3

Just looking through code on git I'm seeing: int NewCircuitPeriod; /**< How long do we use a circuit before building... **/ Which makes me think that if "10s of hours" in seconds is easily overflowing an int. try around 30000 maybe?


3

I don't think there's any limit other than inherited from the protocol, i.e. 2^16. The code does suggest that all stream IDs (other than 0) are acceptable for streams.


3

@Jens's answer has a great description of current Tor. The Tor-Browser adds some additional defenses, namely: it enables HTTP pipelining, so that several requests can be sent on the same "batch" it reorders the packets in that batch and randomly sets its size


3

Tor can change circuit while accessing a web page but it will not cause problems except in special cases. The explanation is below. Current browsers and web servers - few TCP connections needed Usual web pages contain a lot of resources (text, images, videos, styles, scripts...) which could all be downloaded in a single TCP connection when all the ...


Only top voted, non community-wiki answers of a minimum length are eligible