Bitcoin Core contributors are weighing whether or not a thinly used community transport gives useful insurance coverage or has turn into a legal responsibility too expensive to retain.
Within the open CJDNS help dialogue, Bitcoin Core member Andrew Chow stated one seeder database held 25 CJDNS addresses, had reached 22 and categorised solely seven nearly as good. The problem creator, Martin Zumsande, reported seeing solely three to 4 friends although Bitcoin Core ships with 11 fastened CJDNS seeds.
These figures have prompted help for deprecation and a suggestion that Bitcoin Core warn customers in a 32.x launch earlier than planning elimination in 33.x. However that model sequence was posed as a query. As of Sunday, Aug. 23, the difficulty remained open within the 32.0 milestone, with its Improvement part empty of an implementation department or pull request.
Bitcoin Core implements CJDNS as elective peer-to-peer transport and deal with dealing with, outdoors Bitcoin’s consensus system. Situation #36041 as an alternative asks whether or not Bitcoin Core ought to hold CJDNS deal with dealing with as a fallback when the skinny peer pool can also make CJDNS-only nodes simpler to encompass.
Bitcoin Core’s seven good nodes seize one seeder snapshot
The seeder numbers describe one crawler’s database at one time limit. The worldwide CJDNS inhabitants could also be bigger as a result of the determine covers solely that crawler’s database.
The seeder applies “good” as a stricter technical filter than reachability. In Chow’s DNSSeedrs implementation, a node should go checks protecting its port, marketed community service, protocol model, chain peak and rolling reliability. The reliability checks use a number of time home windows and require minimal try counts. That explains how the seeder may attain 22 addresses whereas classifying solely seven nearly as good.
Solely seven of the 22 reached addresses cleared the good-node filters, leaving the usable pool shallow. Zumsande’s node discovered simply three or 4 friends, and he provided low triple digits as a tough stage which may justify continued help. The low-triple-digit benchmark was Zumsande’s alone, giving maintainers a quantity to argue over as an alternative of solely a common criticism about low utilization.
Peer-count arithmetic alone leaves the eclipse price unknown. Bitcoin Core usually maintains eight full-relay outbound connections and two block-relay-only connections, with an occasional feeler or additional block-relay-only connection. A contributor advised grounding any CJDNS threshold in the price of filling these common slots and eclipsing a CJDNS-only node.
An eclipse assault isolates a node by monopolizing the friends that form its view of the community. On a transport with a small recognized deal with set, an attacker has a extra concentrated goal. Bitcoin Core’s present CJDNS documentation already discourages CJDNS-only operation as a result of a node might fail to fill its outbound slots, repeatedly strive the few addresses it is aware of and turn into extra inclined to Sybil assaults.
A profitable eclipse is dependent upon greater than the ten common outbound slots. The general public dialogue leaves the total assault price unquantified. Handle availability, deal with choice, crawler reliability gates and occasional additional outbound connections all have an effect on sensible publicity. The measured pool helps a focus concern for CJDNS-only nodes, whereas the price of exploiting that concern stays unquantified.
Redundancy is dependent upon how CJDNS is used
CJDNS gives a special proposition when it’s one path amongst a number of. Bitcoin Core’s documentation presents it as a complementary choice alongside IPv4, IPv6, Tor and I2P, permitting a node to maintain one other route out there if one community has issues.
That choice has turn into simpler to make use of. CJDNS 22.1 launched DNS-seeded auto-peering on Jan. 8, 2025, making guide peer addition elective. Bitcoin Core then merged up to date setup documentation on March 30, 2026, changing out of date manual-peering directions with the newer stream.
These modifications lowered setup friction. Any impact on Bitcoin’s CJDNS peer inhabitants stays unmeasured. Bitcoin Core merged one other documentation change on Aug. 18, 2026, explicitly discouraging CJDNS-only use as a result of the deal with pool remained too small to fill outbound slots reliably.
CJDNS-only and mixed-network operators due to this fact face completely different stakes. A CJDNS-only operator faces the thin-pool danger that the documentation now warns about. A mixed-network operator makes use of CJDNS for elective route variety and might retain different automated paths even when CJDNS has few friends.
A future deprecation would take away transport settings whereas leaving block-validity guidelines unchanged. Bitcoin Core added full CJDNS help in model 23.0 as a P2P networking function. The controversy is confined to deal with dealing with and connection choices; Bitcoin’s consensus and block-validity guidelines sit outdoors its scope.
The straight affected operators could be these utilizing -cjdnsreachable, which tells Bitcoin Core to deal with the related IPv6 vary as CJDNS, or -onlynet=cjdns, which limits automated outbound connections to that transport. The identical choice can presently be mixed with different networks, whereas inbound and manually added connections stay out there underneath -onlynet, in line with the documentation.
Situation #36041 stays open, with the warning and elimination sequence recorded solely as a proposal. It reveals a small noticed peer set, a number of expressions of help for deprecation and one proposed launch sequence. It additionally reveals why a utilization rely alone is an incomplete take a look at: backup capability is Most worthy earlier than a main route fails, however a backup community that fails to fill connections might supply much less resilience than its presence within the code suggests.
Bitcoin Core nonetheless helps CJDNS. A merged warning or elimination pull request would change the standing of the talk. Seven good nodes makes the transport-diversity tradeoff measurable and leaves the elimination alternative open.
