Afterthought -- Sybil attacks are not possible in cryptocurrency, no? Because no reputation ratings.

[amanda_b_johnson]

A Sybil attack is defined as "an attack wherein a reputation system is subverted by forging identities in peer-to-peer networks." (via Wikipedia and accorded by other sites)

Dash's masternodes aren't launched or paid based on peer-given reputation scores. They are paid if they have collateral, exist, and do their jobs. Period.

So... I guess I'm just saying... if anyone else ever gets the Sybil attack question -- I believe it's actually irrelevant.

Edit: A Sybil attack is possible in systems like Bitshares, where nodes/stakers are voted upon democratically with coin votes. But not in Dash.

 

[TaoOfSatoshi]

Kristov Atlas had this to say about Sybil attacks in Darkcoin (from 2014):

Source:

http://cdn.anonymousbitcoinbook.com/darkcoin/darksend-paper/Atlas_Darksend-Analysis-v002.pdf

And this was Evan's reply:

Source:

https://www.dash.org/forum/threads/reply-to-kristovs-paper.2325/

"Sybil Attack

In a Sybil attack, the attacker subverts the reputation system of a peer-to-peer network by creating a large number of pseudonymous identities. This allows an attacker to gain information by observation.

One of the most serious attack vectors found was a sybil attack on a two-peer Darksend denominated transaction. Requiring as few as two peers for Darksend transactions was never intended to be used beyond the scope of testing. As of RC5 this issue has been resolved.

Other sybil-type attacks (such as the active denial to sign) are mitigated by the use of collateral in the core protocol, which is actively used in RC5.

It’s worth noting that Darksend is not the only technology vulnerable to Sybil attack. All peer-to-peer systems have to deal with Sybil attacks, including Bitcoin and Cryptonote currencies."

So there's a bit more info for you @amanda_b_johnson.

 

[Miner237]

the first and second tier nodes will require resources and electricity to run there is a cost and reward for both, not sure why i keep reading about no cost second tiers.

the review says master nodes are not relevant? but theoreticly couldn't a single owner of all master nodes reveal private send transaction history?

 

[AndyDark]

Sybil attack refers to owning enough peers, then there is a 51% attack referring to owning enough hashpower.

The main attack to prevent is double-spending which both Bitcoin & Dash tier-1 network are vulnerable if the attacker owns enough hashrate (actually less than 51%).

Dash's tier-2 network (opt-in decentralized services that in Bitcoin are provided by centralized services out-of-band) the consensus is quorum-based so an attacker needs to buy control of enough masternodes to e.g. double-spend using InstandSend or record enough joins in multi-round PrivateSend mixes, but the % is a lot higher than 51% to subvert quorums and the cost of that attack is orders of magnitude higher than 51% attacking the hashrate, not to mention the increasing cost of the attack as supply was bought up.

None of these attacks let users lose funds, but they can let the attacker double spend their own funds potentially, depending on how much they are willing to spend.

 

[amanda_b_johnson]

Thanks, all, for your helpful and informative responses thus far.