Bitcoin Core Merges Privacy Fix Into v32; v31 Backport Pending

Bitcoin Core merged a fix for a privacy risk affecting private-broadcast connections into its v32 code branch on Oct. 1. The change first entered the main development branch on Sept. 25. A backport to the v31 branch remains open.

The fix addresses a risk that could allow an observer to link a private-broadcast connection to a node’s regular activity. A proposal to backport the change received approval from reviewer vasild on Oct. 6 and was assigned to the 31.2 milestone. The milestone does not include a release date.

Bitcoin Core’s official download page lists v31.1 as the latest stable release. The v32.0 download directory contains release-candidate files rather than a final release, including RC3 binaries dated Oct. 6.

Private broadcast is disabled by default. Users who enable the privatebroadcast option can submit transactions through sendrawtransaction, a command that sends raw transactions to the Bitcoin network. The feature creates short-lived connections to Tor or I2P peers and to IPv4 and IPv6 peers reached through Tor.

The issue involved Bitcoin Core’s handling of peers that misbehave. The software can discourage such peers, and that process can affect other connections using the same peer address. Reviewers found that these effects could reveal whether a private-broadcast connection was linked to a node’s ordinary connections.

The fix separates the two types of handling. Private-broadcast peers are excluded from the standard discouragement process, while a private peer that misbehaves can still be disconnected. Discouraging an ordinary peer can no longer disconnect a private-broadcast connection that uses the same address.

The repair is separate from an earlier privacy fix included in v31.1. That change addressed cases in which private-broadcast connections used a clearnet connection instead of the privacy network selected by the user. The newer fix concerns information revealed through peer-handling behavior rather than the connection’s route.

Bitcoin Core developers classify private broadcast as experimental and describe it as a tool for reducing specific privacy risks. The feature remains disabled in the default configuration.