Tor 是一個免費使用的去中心化網路，專為盡可能多地使用互聯網而設計。 如果使用得當，該網路可以實現私人和匿名瀏覽和通信。
## 工作原理
Tor 的工作原理是通過一個由數千個志願者運行的服務器組成的網絡路由您的流量，稱為節點（或中繼）。
每當您連接到 Tor 時，它都會選擇三個節點來構建通往網際網路的路徑，這種路徑稱為「電路」。 每個節點都有自己的功能：
### 入口節點
入口節點，通常稱為守護節點，是Tor客戶端連接的第一個節點。 入口節點能夠看到您的 IP 位址，但無法看到您正在連接的內容。
Unlike the other nodes, the Tor client will randomly select an entry node and stick with it for two to three months to protect you from certain attacks.[^1]
### 中間節點
中間節點是 Tor 客戶端連接的第二個節點。 它可以看到流量來自哪個節點（入口節點）以及它下一步要去哪個節點。 中間節點無法看到您的 IP 位址或您連接的網域。
對於每個新電路，中間節點會從所有可用的 Tor 節點中隨機選擇。
### 出口節點
出口節點是您的 Web 流量離開 Tor 網路並轉發到所需目的地的點。 The exit node is unable to see your IP address, but it does know what site it's connecting to.
2. 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.
3. 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.
[^1]: 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](https://blog.torproject.org/improving-tors-anonymity-changing-guard-parameters) and [paper](https://www-users.cs.umn.edu/~hoppernj/single_guard.pdf) on entry guards. ([https://support.torproject.org/tbb/tbb-2/](https://support.torproject.org/tbb/tbb-2/))
[^2]: 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](https://metrics.torproject.org/glossary.html))
