TL;DR: Mimblewimble developers David Burkett, Jasper, @joltz, Quentin Le Sceller, and Yeastplume collaborated on a response to a widely cited Dragonfly Research report, claiming fundamental flaws in the Grin project’s privacy model.
Mimblewimble Devs Respond to Dragonfly Research Attack Claims
Breaking Mimblewimble’s Privacy Model made the rounds among crypto privacy enthusiasts in large part because of its associated coin, Grin, is very much embraced by usually sour BTC maximalists. “Using only $60/week of AWS spend,” Dragonfly’s Ivan Bogatyy explained, “I was able to uncover the exact addresses of senders and recipients for 96% Grin transactions in real time. The problem is inherent to Mimblewimble, and I don’t believe there’s a way to fix it. This means Mimblewimble should no longer be considered a viable alternative to Zcash or Monero when it comes to privacy.”
To counter, Mimblewimble developers insisted recently Bogatyy’s supposed attack is in actuality “the well-documented and discussed transaction graph input-output-linkability problem. This is not new to anyone on the Grin team or anyone who has studied the Mimblewimble protocol. Grin acknowledged the ability to link outputs on chain in a Privacy Primer published on its public wiki in November 2018, before mainnet was launched. This problem encompasses Ian Mier’s ‘Flashlight attack,’ which we have listed as one of our Open Research Problems.”
Devs further described Dragonfly assertions as “factually inaccurate,” full of “logical leaps that are not substantiated via the network analysis exercise that is described.” Grin team members have long held its privacy-centric emphasis is a work in progress. And while Bogatyy’s attack hinges on what’s known as a “linkability” vector, Burkett et al stress in their response “it does not ‘break’ Mimblewimble nor is it anywhere close to being so fundamental as to render it or Grin’s privacy features useless.”
They also keyed upon six points in attempting to shut down Bogatyy’s assertions. Mimblewimble itself doesn’t have addresses to be linked in the first place, and instead coins are exchanged through one-time outputs. As such, Dragonfly couldn’t link addresses because there are none, which is not a small point as Bogatyy assumed governments could track users through his linkability attack. Nearly 100% collection of network transactions seems outstanding and compelling at first read, but Grin devs aren’t sure “what exactly is being identified here or what else the author is able to accomplish with this information,” they retorted. The response continues along these lines, and it appears the Mimblewimble community was more taken aback by the press coverage Dragonfly’s article received than the actual substance of the attack.
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