Coordinator-instantiated milestone partitioning attack

[ercw]

Issue:
Since IOTA is currently specially vulnerable to 51% attacks, a rogue Coordinator could present two separate milestones using identical index numbers to the network and sustain a partitioning attack long enough to successfully double-spend on the network.

Theory:
IOTA is currently only protected against reorg-attacks by virtue of the Coordinator. In the case that the attack is launched using a compromised Coordinator private key (or if the IOTA Foundation is simply malicious), then there is no such protection. The Coordinator would issue two different milestone transactions with the same index numbers which would split the network into two parts. The Coordinator would then keep incrementing the two milestones separately. Simultaneously, to ensure that no subtangle overtakes the other and to prevent the network from converging, the Coordinator would abuse the fact that IOTA currently has very low hashpower and ensure that both subtangles are sustained by producing PoW (by spamming transactions) on whichever subtangle that needs it long enough for a double-spend to confirm on economically important nodes.

Suggested fix:
A kill-switch mechanism could be implemented in clients in order to halt the network in the case of a milestone partitioning attack. If two milestone transactions with the same index numbers but different hashes are detected in the validateMilestone-function a node could cease all operations and start spamming the network indefinitely with a new type of transaction alerting other nodes of the attack, presenting the proof of the two milestones with same index but different hashes. Nodes that see this special transaction could enter the same behavior. This should make attempts at milestone partitioning attacks less feasible for the Coordinator.

[mariodian]

Why was this closed immediately instead of being addressed?

[TbLtzk]

At least a rational for refuting the suggestion would be interesting

[scipsycho]

yeah, it at least should have been given an explanation.

[tactical-drone]

In the case that the attack is launched using a compromised Coordinator private key