Some people argue that Iota is centralised because of the use of a coordinator to issue milestones which, in turn, are used as a root of trust to verify transactions.

What would happen to the network (with the current IRI) if the coordinator vanishes?

  • Keep in mind that in the scenario suggested by the OP, old milestones still exist in tangle. The question is "what append if there is no new milestone issued ?"
    – ben75
    Jul 22, 2018 at 14:17

2 Answers 2


No more confirmation by the coo, the tangle will keep growing, but none of the new transactions will be confirmed.

With the current IRI (1.5.1), the starting point of the random walk is a "not too old" milestone. If there is no more new milestones the random walk will probably became more and more expensive to run. So the selection of transactions to approve (on regular IRI) will slow down. I guess that most instances will start to crash by lack of resources (I expect that the RAM required by the random walk will be the bottleneck).

After reboot, the IRIs will rebuild a new tangle using the latest milestone as a starting point... and crash again...


There won't be any 100% confirmed transactions anymore. The tangle will then rely on the fact that the majority of people will follow same path in tangle as COO referenced before.

Random walk should not become much more expensive here as well, since the time when IOTA is ready to remove the COO it will be such a high number of transactions ( and thus network bound pow will be very high ), that an attack (side tangle , double spend) won't be a trivial task.

see also https://blog.iota.org/confirmation-rates-in-the-tangle-186ef02878bb

The value alpha for example helps to calibrate confirmations rate in that scenario. A high value of alpha would help to strengthen the confirmation rate and reduce the amount of time spent in random walk.

  • network pound pow is the combined pow work the network is able to do. Since it is not possible to attack the network solely in one spot you would have to attack the network globally (with 34% of hashing power) in order to have a chance to build a new tangle. That will be increasingly difficult with a higher transaction rate of the network. Jul 22, 2018 at 11:06
  • any insights on where the 26,000,000 magic number comes from? its not even trinary :) Jul 22, 2018 at 11:18
  • as stated in comments section there, it is a theoretic number and using blockchain concepts regarding the caluculations. IMO this is not applicable in a tangle having rules on tip selection and also regarding network limitations. It would not be feasable to be "faster" than the tangle evolves. Like you said you would run into DDOS before. Also lazy tips are not likely to be considered. So in the end you are just not quick enough to gain omnipresence in the network, no matter what attack you build Jul 22, 2018 at 11:49
  • 2
    There is no better theoretical number however. It may be wise for someone to answer the question with better numbers. Jul 22, 2018 at 19:27
  • The very notion of a "magic number" (or set of magic numbers) is absurd. See my answer here iota.stackexchange.com/questions/48/…
    – user482
    Jul 25, 2018 at 0:57

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