> On Jun 30, 2016, at 6:52 PM, Peter Todd <p...@petertodd.org> wrote: > >> On Thu, Jun 30, 2016 at 05:22:08PM +0200, Eric Voskuil via bitcoin-dev wrote: >> >>> On Jun 30, 2016, at 2:43 PM, Jonas Schnelli <d...@jonasschnelli.ch> wrote: >>> >>>>>> The core problem posed by BIP151 is a MITM attack. The implied solution >>>>>> (BIP151 + authentication) requires that a peer trusts that another is >>>>>> not an attacker. >>>>> >>>>> BIP151 would increase the risks for MITM attackers. >>>>> What are the benefits for Mallory of he can't be sure Alice and Bob may >>>>> know that he is intercepting the channel? >>>> >>>> It is not clear to me why you believe an attack on privacy by an anonymous >>>> peer is detectable. >>> >>> If Mallory has substituted the ephemeral keys in both directions, at the >>> point where Alice and Bob will do an authentication, they can be sure >>> Mallory is listening. >> >> I understand the mechanics of a tunnel between trusting parties that have a >> secure side channel. But this assumes that no other peer can connect to >> these two nodes. How then do they maintain the chain? >> >> The "middle" in this sense does not have to be the wire directly between >> these two peers. It can be between either of them and any anonymous >> connection they (must) allow. >> >> Of course this creates pressure to expand their tunnel. Hence the problem of >> expanding node identity in an effort to preserve privacy. The protection >> will remain weak until the entire network is "secure". At that point it >> would necessarily be a private network. >> >> As Pieter rightly observes, there are and always will be tunnels between >> trusting nodes. Often these are groups of nodes that are in collaboration, >> so logically they are one node from a system security standpoint. But if >> people become generally reliant on good node registration, it will become >> the registrar who controls access to the network. So my concern rests I this >> proposal becoming widely adopted. > > To be clear, are you against Bitcoin Core's tor support? > > Because node-to-node connections over tor are encrypted, and make use of onion > addresses, which are self-authenticated in the exact same way as BIP151 > proposes.
BIP151 is self-admittedly insufficient to protect against a MITM attack. It proposes node identity to close this hole (future BIP required). The yet-to-be-specified requirement for node identity is the basis of my primary concern. This is not self-authentication. > And we're shipping that in production as of 0.12.0, and by default Tor onion > support is enabled and will be automatically setup if you have a recent > version of Tor installed. > > Does that "create pressure to expand node identity"? The orthogonal question of whether Tor is safe for use with the Bitcoin P2P protocol is a matter of existing research. e _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
