[tor-talk] M.Hearn adds privacy depriority to Bitcoin XT, calls your Tor/Proxy/etc use "unimportant"

Sean Lynch seanl at literati.org
Fri Aug 28 17:03:03 UTC 2015

On Tue, Aug 18, 2015 at 7:07 PM grarpamp <grarpamp at gmail.com> wrote:

> http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-August/010379.html
> https://github.com/bitcoinxt/bitcoinxt/commit/73c9efe74c5cc8faea9c2b2c785a2f5b68aa4c23
> Bitcoin XT contains an unmentioned addition which periodically downloads
> lists of Tor IP addresses for blacklisting, this has considerable privacy
> implications for hapless users which are being prompted to use the
> software. The feature is not clearly described, is enabled by default,
> and has a switch name which intentionally downplays what it is doing
> (disableipprio). Furthermore these claimed anti-DoS measures are
> trivially bypassed and so offer absolutely no protection whatsoever.
The feature is very clearly described on the BitcoinXT web site, and you're
mischaracterizing it by saying BitcoinXT downloads the list "for
blacklisting." It is a DoS protection feature that ONLY comes into play
under overload. And yes, BitcoinXT considers Tor connections "less
important" than non-anonymous connections during attacks. You may not agree
that that's a good heuristic, but if that's your problem with it, say so.

>From https://bitcoinxt.software/patches.html:

"Anti-DoS attack improvements, by Mike Hearn. It's currently possible to
jam a Bitcoin node by connecting to it repeatedly via different IP
addresses, as there is a fixed limit on how many connections a node will
accept. Once full, no other peers or wallets can connect to it any more and
serving capacity for new nodes and P2P wallets is reduced. If the attack is
repeated against every node, the entire network could become jammed.

"This patch set introduces code that runs when a node is full and otherwise
could not accept new connections. It labels and prioritises connections
according to lists of IP ranges: if a high priority IP address connects and
the node is full, it will disconnect a lower priority connection to make
room. Currently Tor exits are labelled as being lower priority than regular
IP addresses, as jamming attacks via Tor have been observed, and most
users/merchants don't use it. In normal operation this new code will never
run. If someone performs a DoS attack via Tor, then legitimate Tor users
will get the existing behaviour of being unable to connect, but mobile and
home users will still be able to use the network without disruption."

Please specify how that is "misleading" or "downplaying."

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