Grin Devs Respond: Mimblewimble Privacy Isn't 'Fundamentally Flawed'

The developers of privacy-centric cryptocurrency Grin have hit back at the fundamental claims of an article purporting to have "Broken" the coin's privacy model.

In a Medium blog post published on Nov. 19, Grin core dev Daniel Lehnberg argued that the so-called breakage did not go beyond the already-acknowledged privacy limitations of the coin's protocol and relied on a passive attack vector that would be insufficient to glean actionable data.

These obfuscate sensitive transaction data rather than showing plaintext transaction values and can prevent double-spending while improving privacy.

As outlined in Cointelegraph's coverage yesterday, Bogatyy had focused on the use of a default, supplemental feature to MimbleWimble called CoinJoin, which creates small "Anonymity sets" by combining encrypted inputs into a single large transaction in such a way as to make it is difficult to distinguish which inputs are paying which outputs.

Bogatyy also claimed to have conducted a successful "Attack" on a supplemental feature called "Dandelion" that is used by Grin to reduce the chance of so-called "Spy nodes" recording transactions before cut-through, while they are still in an unconfirmed transaction pool.

While the limitations of Grin's overall privacy model - which is significantly more complex than space permits to outline here - are known, Lehnberg's critique of Bogatyy's research rests on what he judges to be key "Inconsistencies."

These include the implication that it would be possible for law enforcement to link intercepted data to a user address - when, as Lehnberg states, addresses do not exist within Grin's privacy model at all.

"The Grin team has consistently acknowledged that Grin's privacy is far from perfect. While transaction linkability is a limitation that we're looking to mitigate as part of our goal of ever-improving privacy, it does not 'break' Mimblewimble nor is it anywhere close to being so fundamental as to render it or Grin's privacy features useless."

As reported, Grin underwent its first network hard-fork this summer to introduce tweaks to its consensus algorithm in order to achieve greater resistance to ASIC miners.

In October, the Litecoin Foundation published two new draft proposals that pave the way toward integrating MimbleWimble in order to establish privacy features for the Litecoin network.