Tor Hidden Service

A Tor hidden service - now officially called an onion service - is a network endpoint that's only reachable through the Tor network, identified by a .onion address. The endpoint's real IP location is hidden from both the user and the wider internet.

For a Bitcoin node, running as a Tor onion service provides:

• Network-layer privacy. Your real IP doesn't appear in peer lists, isn't visible to chainalysis firms scanning the gossip network, and isn't logged by other node operators.
• Censorship resistance. Governments or ISPs that try to block Bitcoin can block IP ranges, but blocking Tor itself is much harder (and crosses a much higher political line).
• Protection against eavesdropping attacks. Without your IP, observers can't easily correlate your broadcasts with your physical location or identity.
• Protection against eclipse attacks. Tor's random circuit selection makes it much harder for an attacker to predict or target your specific outbound peers.

The cost is latency. Tor adds ~200-500ms of round-trip time over normal internet routes due to its three-hop relay structure. For Bitcoin's needs - block propagation every ~10 minutes, transactions that propagate over seconds - this latency is essentially invisible in practice. Block- and transaction-relay over Tor work fine.

Bitcoin Core has shipped first-class Tor support since 2014. Running your node behind Tor is a single config-file change (proxy=127.0.0.1:9050 plus a few related options). Many node-in-a-box products (Umbrel, Start9, RaspiBlitz) ship with Tor enabled by default. The same hidden-service pattern can also expose RPC for remote management, letting you control your home node from anywhere without opening any firewall ports.

For self-custody users running a full node, running over Tor is the single biggest privacy upgrade you can make at the network layer. Strongly recommended for anyone who cares about not having their on-chain activity correlated with their home IP.