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| Panoramica Tor | simple/torproject | Tor è una rete decentralizzata e gratuita progettata per utilizzare Internet con la massima privacy possibile. |
Tor è una rete decentralizzata e gratuita progettata per utilizzare Internet con la massima privacy possibile. Se utilizzata correttamente, la rete consente di navigare e comunicare in modo privato e anonimo.
Path Building to Clearnet Services
"Clearnet services" are websites which you can access with any browser, like privacyguides.org. Tor lets you connect to these websites anonymously by routing your traffic through a network comprised of thousands of volunteer-run servers called nodes (or relays).
Every time you connect to Tor, it will choose three nodes to build a path to the internet—this path is called a "circuit."
Ciascuno di questi nodi ha una propria funzione:
Il nodo di ingresso
Il nodo di ingresso, spesso chiamato nodo di guardia, è il primo nodo a cui si connette il client Tor. Il nodo di ingresso è in grado di vedere il tuo indirizzo IP, ma non è in grado di vedere a cosa ti stai connettendo.
A differenza degli altri nodi, il client Tor seleziona casualmente un nodo di ingresso e vi rimane per due o tre mesi per proteggerti da alcuni attacchi.1
Il nodo centrale
Il nodo centrale è il secondo nodo a cui si connette il client Tor. Può vedere da quale nodo proviene il traffico, il nodo di ingresso, e a quale nodo va successivamente. Il nodo centrale non può vedere il tuo indirizzo IP o il dominio a cui ti stai connettendo.
Per ogni nuovo circuito, il nodo centrale viene selezionato a caso tra tutti i nodi Tor disponibili.
Il nodo di uscita
Il nodo di uscita è il punto in cui il traffico web lascia la rete Tor e viene inoltrato alla destinazione desiderata. Il nodo di uscita non è in grado di vedere l'indirizzo IP, ma sa a quale sito ti stai collegando.
Il nodo di uscita sarà scelto a caso tra tutti i nodi Tor disponibili con un flag di uscita.2
Path Building to Onion Services
"Onion Services" (also commonly referred to as "hidden services") are websites which can only be accessed by the Tor browser. These websites have a long randomly generated domain name ending with .onion.
Connecting to an Onion Service in Tor works very similarly to connecting to a clearnet service, but your traffic is routed through a total of six nodes before reaching the destination server. Just like before however, only three of these nodes are contributing to your anonymity, the other three nodes protect the Onion Service's anonymity, hiding the website's true IP and location in the same manner that Tor Browser is hiding yours.
Crittografia
Tor encrypts each packet (a block of transmitted data) three times with the keys from the exit, middle, and entry node—in that order.
Once Tor has built a circuit, data transmission is done as follows:
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Firstly: when the packet arrives at the entry node, the first layer of encryption is removed. In this encrypted packet, the entry node will find another encrypted packet with the middle node’s address. The entry node will then forward the packet to the middle node.
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Secondly: when the middle node receives the packet from the entry node, it too will remove a layer of encryption with its key, and this time finds an encrypted packet with the exit node's address. The middle node will then forward the packet to the exit node.
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Lastly: when the exit node receives its packet, it will remove the last layer of encryption with its key. The exit node will see the destination address and forward the packet to that address.
Below is an alternative diagram showing the process. Each node removes its own layer of encryption, and when the destination server returns data, the same process happens entirely in reverse. For example, the exit node does not know who you are, but it does know which node it came from, and so it adds its own layer of encryption and sends it back.
Tor allows us to connect to a server without any single party knowing the entire path. The entry node knows who you are, but not where you are going; the middle node doesn’t know who you are or where you are going; and the exit node knows where you are going, but not who you are. Because the exit node is what makes the final connection, the destination server will never know your IP address.
Caveats
Though Tor does provide strong privacy guarantees, one must be aware that Tor is not perfect:
- Well-funded adversaries with the capability to passively watch most network traffic over the globe have a chance of deanonymizing Tor users by means of advanced traffic analysis. Nor does Tor protect you from exposing yourself by mistake, such as if you share too much information about your real identity.
- Tor exit nodes can also monitor traffic that passes through them. This means traffic which is not encrypted, such as plain HTTP traffic, can be recorded and monitored. If such traffic contains personally identifiable information, then it can deanonymize you to that exit node. Thus, we recommend using HTTPS over Tor where possible.
If you wish to use Tor for browsing the web, we only recommend the official Tor Browser—it is designed to prevent fingerprinting.
Risorse aggiuntive
- Manuale d'uso del Tor browser
- Come funziona Tor - Computerphile (YouTube)
- Tor Onion Services - Computerphile (YouTube)
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The first relay in your circuit is called an "entry guard" or "guard". It is a fast and stable relay that remains the first one in your circuit for 2-3 months in order to protect against a known anonymity-breaking attack. The rest of your circuit changes with every new website you visit, and all together these relays provide the full privacy protections of Tor. For more information on how guard relays work, see this blog post and paper on entry guards. (https://support.torproject.org/tbb/tbb-2/) ↩︎
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Relay flag: a special (dis-)qualification of relays for circuit positions (for example, "Guard", "Exit", "BadExit"), circuit properties (for example, "Fast", "Stable"), or roles (for example, "Authority", "HSDir"), as assigned by the directory authorities and further defined in the directory protocol specification. (https://metrics.torproject.org/glossary.html) ↩︎