How SABRE Tech Can Stop Hackers From Splitting Bitcoin Into Two

If hackers felt like it, they could split bitcoin in two.

As described in a new white paper, they've invented a relay network called SABRE that they hope will one day be built on top of bitcoin.

With the same name as the curved blade common in the Napoleonic era, SABRE sounds like it would be used to slice bitcoin in half.

That's why it can be used to access data the attacker isn't supposed to be able to see - or to steal cryptocurrency, as hackers have done several times in the past, by using BGP to redirect traffic from bitcoin miners to themselves.

"An [AS] level attacker can partition the bitcoin into two disjointed components by first hijacking and then dropping traffic exchanged between them."

ETH Zurich researchers think they can prevent the attack with a so-called "Relay network." SABRE is a proposed network that would be managed by one entity, providing bitcoin nodes with an "Extra secure channel" for moving blocks across the network.

A bitcoin node needs to just connect to one of them to take advantage of its capability for keeping it connected to other nodes.

Why can't the attack just switch targets and fool the SABRE nodes instead? The researchers propose a little hack: They only place the SABRE nodes in "Cherry-picked" ASes with certain characteristics that make them harder to hijack.

"So, the [central] idea on their work is that if you run a relay network with nodes on diversely placed /24 announcements, it's much harder for a route hijacker to disrupt it," explained long-time Bitcoin Core developer Gregory Maxwell, discussing the idea in the IRC chat channel "Bitcoin wizards."

He's not convinced a "Large-scale" attack is very likely, partly because "There are many redundant ways" bitcoin nodes are connected already.