Onion routing
Also · Sphinx
Onion routing wraps a Lightning payment in layers of encryption so that each hop learns only the previous and next node, never the full path or the endpoints.
When a Lightning payment crosses several nodes, the sender encrypts the routing instructions in nested layers, 1 per hop, using the Sphinx construction. Each node peels off its own layer, reads where to forward and how much, and passes the rest on. It cannot tell whether the previous node was the sender or just another hop, nor whether the next is the final recipient.
This gives Lightning better payment privacy than on-chain Bitcoin, where every transfer is public forever. It does not make Lightning anonymous. Intermediate nodes see amounts and timing, channel balances can be probed, and the endpoints’ own behaviour leaks information. Privacy depends on the topology as much as on the cryptography.
In French · Routage en oignon