Tor Exit Nodes & .Onion Site IPs

TL;DR

No, a Tor exit node cannot directly know the IP address of an .onion site (hidden service). This is by design. .Onion sites use multiple layers of encryption and routing to hide their location. However, an attacker controlling enough relays *could* potentially correlate traffic patterns to infer information.

Understanding How Tor Works

Before we dive into why exit nodes can’t see .onion site IPs, let’s quickly cover how Tor works:

• Your Connection: When you use Tor, your traffic is routed through a series of relays (nodes) before reaching its destination.
• Encryption Layers: Each relay adds a layer of encryption, making it difficult to trace the origin and destination of the data.
• Hidden Services (.Onion Sites): These sites don’t have a fixed IP address. They use a special process to create rendezvous points within the Tor network.

Why Exit Nodes Can’t See .Onion Site IPs

1. Rendezvous Points: When you connect to an .onion site, your Tor client and the hidden service both choose a series of rendezvous points (relays). Communication happens *between* these points. The exit node only sees traffic going to/from the final rendezvous point, not directly to the hidden service.
2. Encryption: Even at the rendezvous point, the data is encrypted. The exit node doesn’t have the keys to decrypt it and see the .onion site’s address.
3. Hidden Service Protocol: The hidden service protocol (used for .onion sites) specifically avoids revealing the server’s IP address to any Tor nodes. It uses introduction circuits to establish a connection without exposing its location.

What an Exit Node *Can* See

An exit node can see:

• The destination website: If you’re visiting a regular website (not .onion), the exit node sees the domain name and IP address of that site.
• Encrypted traffic: The exit node sees encrypted data going to/from the rendezvous point when connecting to an .onion site, but can’t decipher it.
• Timing information: An attacker controlling many relays could potentially try to correlate timing patterns of connections to infer something about the hidden service’s location, but this is very difficult and unreliable.

Example: Connecting to an .Onion Site

Imagine you want to visit example.onion:

1. Your Tor client finds a series of relays (including rendezvous points).
2. The hidden service also chooses its own set of relays.
3. Communication is established between your client and the hidden service via these rendezvous points.
4. The exit node only sees traffic going to/from the final rendezvous point, not example.onion directly.

Checking Your Tor Connection

You can verify that your IP address is hidden from websites you visit using a site like:

https://check.torproject.org/

Important Considerations for cyber security

• Compromised Relays: While Tor is designed to be secure, if enough relays are compromised by an attacker, they *could* potentially correlate traffic patterns and attempt to deanonymize users or hidden services. This is a complex attack and requires significant resources.
• End-to-End Encryption: Always use end-to-end encryption when communicating with .onion sites (e.g., HTTPS).