How to Configure MyFamily on Tor Relays

Running multiple Tor relays helps scale the network, but it requires operators to declare their nodes as a single group using the MyFamily configuration. This article covers the purpose of the Tor family setting, why it is critical for protecting user anonymity against traffic correlation attacks, and the exact steps required to implement mutual family declarations in the torrc configuration file.

What is a Tor Relay Family?

The MyFamily setting is a directive in the Tor configuration file (torrc) that tells Tor directory authorities and clients that a specific set of relays is controlled by the same person, group, or organization.

When a Tor client builds a three-hop circuit (Guard, Middle, and Exit relays) to browse the web, it selects relays randomly based on bandwidth and flags. If a single entity controls both the Guard relay (which sees the user’s real IP address) and the Exit relay (which sees the destination website), that entity could correlate traffic timing and deanonymize the user. By properly declaring a family, clients are instructed never to use more than one relay from that family in a single circuit.

How to Configure MyFamily

To configure a family, you must add the MyFamily configuration line to the torrc file of every relay you operate.

1. Retrieve the Relay Fingerprint

Always use the relay’s 40-character cryptographic identity fingerprint rather than its nickname, as nicknames are not guaranteed to be unique. You can find your relay’s fingerprint in the fingerprint file located in the Tor data directory (typically /var/lib/tor/fingerprint on Linux) or by checking your Tor logs on startup.

A standard fingerprint looks like this: $2556487E136D74384D0223D9E9DF1D4F1E925EFD

2. Update the torrc File

Open the torrc file on each of your relays and add the MyFamily parameter, followed by a comma-separated list of the fingerprints of all relays in your family.

For example, if you operate three relays (Relay A, Relay B, and Relay C), the MyFamily configuration on all three relays should look identical:

MyFamily $AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, $BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB, $CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC

(Note: While you can include the relay’s own fingerprint in its MyFamily list, it is optional; however, listing all relays uniformly across all nodes simplifies configuration management.)

3. Reload Tor Configuration

After editing the torrc file on each server, reload or restart the Tor process to apply the changes:

sudo systemctl reload tor

Key Rules and Best Practices

• Mutual Declaration is Mandatory: Tor directory authorities enforce a strict mutual agreement policy. Relay A must list Relay B, and Relay B must list Relay A. If the declaration is one-sided, the directory authorities will reject the family relationship, and clients may end up using both relays in the same path.
• Keep the List Updated: Whenever you add a new relay or decommission an existing one, you must update the MyFamily line across every active relay you operate.
• Always Prefix with $: When using 40-character hex fingerprints, prepend each hash with the $ symbol so Tor correctly parses it as an identity key.