The Attack of the Clones against Proof-of-Authority

Transcript

welcome back so next up we have pre Nia Capri Nia PhD student from the University of Sydney who'll be talking about the attack of the clones against proof with authority please welcome onto stage alright hi everyone my name is Maria PhD student at unisza tee-up Sydney ah and the

supervision of Vincent gamle and Guillaume George on today I'm going to present you my work the attack of the clones I can pop up work against brew up Authority sorry ok so first let's have a look at the part research a paper in a triple e p2p in 2013 say that box Shan Mei for due to the network delay and Rock chainsaw should be a why later in 2017 another paper form ITP S&P say that Bitcoin network which is a proof-of-work

blockchain is one about to hurting attacks and last year we wrote that many the video it has can be the various to the post bail on idioms souls in brief we can see that the post pending in abortion is possible with it will attacks ok for a quick recap so what is the boss spending let me show you a concrete example here suppose that we have our Molly the guy at the bottom here Molly has an initial fan of the say $10 Marie want to purchase an item purchase items from a list on the left side and

Bob on the right side suppose that somehow Molly are I mean presumably network can be partitioned into into two paths such in such a way that at least cannot communicate to Bob and Bob cannot communicate to at least so Marie simply sent our $10 to a list over here and Marie also send the same $10 to Bob seen Alice and Bob cannot communicate Alice and Bob believe that their transaction are committed eventually they would get their money so they simply send the item to Molly and assume that the network

petition has come to an end of course we cannot medically create our money from the air one of the transaction will be discarded and Bob Bashara something in the context of blockchain because this issue the post pending and now with the listen arm proof of Authority consensus algorithm we raise the question it is possible to perform the both spending on proof of Authority atriums in order to answer this question let me explain to you how hora which is one of the well

known prove up Authority consensus algorithm let me explain to you how are our okay so be free about aura is who name came from Authority Rao aura is a proof of Authority our horses an algorithm which is available in priority in aura only an occlusive groups up end participant call similar may create dog and insular use its own unique cryptographic key to create blocks a receiver takes turn to Silla Brock and for example are five Silla and one and two and three

info and health I say we begin with arm in one then the next early B and two and three and four and five and he's going to cycle back to N 1 n 2 n 3 and so on and hora also apply a concept up Tom bearson basically a new bra can be created and we turn up its second note that s is configurable each turn is dedicated to only one sailor asilah need to wait for its turn to create a bra again for example of five silver and five second turn as you can see here the

seal on number two need to wear five second after the cylinder number one has created a bra and what would happen if a Scylla doesn't create a broad in its turn for example a sailor may be busy with something else or there might be net well delay or there might be a net worth positional and incident so on and so forth if a sailor cannot create a drop in his turn such a telling you become empty without a bra as indicated in as indicating the speaker with this gray gray square here and auto Scylla may continue to create rocks after empty

turns as you can see at this point there's no dock created by Scylla n2 and n3 may continue to create a box after that now let's talk about Bach finality in Arabic finality will be consider only after a majority ops Allah has created their broth on the shade for example of five Scylla again three Scylla are necessary to finalize the drop as shown in green with this figure we will consider the block yes by n1 here we will consider is finalized

the entry has cleared a block on the shin and what would happen if there is a ND turn in between in this case we still has to wait for a majority of the sealer so entering here will be consider finalized after n1 has put his bra on the shin as you can see we can still achieve minority because we got one two and three here I mean three sila put put their bra on the shin and of course Broxson may fall and the consistent bottom has to come up with a Foley solution in order to reach consensus and

Ferrara the branch with the highest number of bra will be selected as shown in this figure as you can see we have two branches near the upper one and the lower one and in this case the upper one will be selected because it has the higher number of drop in comparison to the low one as to can how a tier 1 2 3 & 4 in comparison to 3 bucks and can bra final degrees during that will position yes it can we can refine already finally a when during the net worth position in this case then his position position are in the vasila into two groups we have at

the first group which consists s are in 1 in 3 and in for another group consists up and 2 and in 5 and you can see that the Brock finality can be reached for the upper branch but not the low one because for the low lower branch we cannot achieve a majority of the ceiling here and in other group you can see that we can achieve the final tree because we have at least 3 out of 5 which is a majority for four facts Allah so to summarize the Brock finality in aura require Stickley

ha so there will be only one partition that may finalize Brock in these examples say we have are the total number ups we have seven total number epsilon here and if there is a nit world partition that's become the sealer into two groups on the left hand side we have four on the right hand side we have three only the sealer a leader sees this group on the left hand side can finalize the block but what would happen if there is one Maria Scylla suppose that emerges Scylla create a cone create is clone to

participate in board partition as you can see in this figure say we have a Macias Scylla indicate by this red guy here and this guy decide to create its clone and participate in a larger partition say we have a Clonezilla here in this case you can see that both partition can finalize the bra and it's going to cause the post pending issue for sure and putting the coning attack to work we conduct experiment to perform the attack against ora our setup consists our nice dealer in two sub networks and we allow the attacker to to

crow and III mean span for the sake of simplicity and also we allow the attacker to partition the network as well so the network will be split into into two sillas groups and in order to perform the attack as soon as the network is partitioned the attacker is going to issue two conflicting transaction one front section two E's Silla groups and then the article simply wears until to transition finalized after that the article simply stop but contribution in one partition so in this case the article may infrared which subgroup that will be selected as a

and how Shane they are at the end updatable Parisian and at the end the Ithaca simply end the network partition and with our experiment the data we tag the obtained show that given the time for 10 turn the attacker can achieve 100% success rate optimal spending because right our in our in our experiment we have Nye Silla but if we eat the pure a network consists of Mozilla probably the attacker need to need to prolong the network position for longer a course and how can we mitigate the league's what

what would be the call to measure so we propose that the simple how to measure would be in straight-up our maturity the algorithm will be more resistant to the to the attack if it requires tickly modern tutor absolute to finalize a bro say for example in our previous case we have nice healers in total strictly modern to tell on I is going to be 7 in this case only one Mozilla cannot it's not enough to perform the attack as you can see that in this case we have one malicious Allah whom a clone himself to

participate in board partition but in this case nature of the position may finalize a Brown so in conclusion with the attack of the clones again prove up Authority the attacker can double spend with 100% success rate from what we have found we also performed the attack against click and not a well-known polarity in all material and you can also find out the detail how we come up video guard him how we perform the attack in in detail we had this link which is going to refer to on a hive and that's the end of my top

thank you for listening yeah so I think in this second last slide you had the countermeasure slide what is there is sort of what would variations of countermeasures may there be ah I think probably an alternative how to measure would be used something like hardware security module in order to to make sure that it's much more difficult to to clone the instant okay thank you