yamada
Member
Quote from: fluffypony on Today at 09:13:41 AM
There are two things that concern me:
1. Outputs can still be linked to addresses. If you send 20 DRK and it sends all these other outputs along with it to obfuscate, the 20 DRK still ends up in someone's address. That this can be observed on the blockchain means that analysis is easy, and we all know how often people leak addresses associated with their wallet (eg. posting it up for giveaways etc. etc.) This is an immutable problem in any Bitcoin-forked cryptocurrency that exists, as the solution (stealth addresses computed w/random data) has to be enforced for every transaction from the genesis block. If you enforce it halfway through you're stuck with old outputs that don't use stealth addresses, which makes it exceedingly complex to ensure the anonymityset is not at-risk.
2. Masternodes are an Achilles' heel. Let us say that there are 10 000 masternodes on the network. Their IP addresses and the port they operate on is, by necessity, known to the network. Let's assume that an attacker controls 5 masternodes of the 10 000. Let's also assume that each of the masternodes on the network is on a dedicated server (none of them use a VPS, because a VPS could be trivially owned by the host operating system) and each of these servers is on a 1gbps unmetered, dedicated port (clearly not the case right now, but I'm talking about a future time). How hard would it be for an attacker to knock the other 9995 masternodes off the network, leaving theirs as the only accessible masternodes (and thus not only earning them all the fees, but giving them perfect insight into transactions moving within their controlled group)? Well, NTP amplification attacks have let attackers launch 400Gbps attacks against a single machine from a sole 2mbps connection. SNMP has a theoretical 650x amplification factor. All an attacker needs to do is max out the unmetered port in an obvious attack, and the datacenter will have to react. Even straight up LOIC-style / botnet SYN floods to the port that the masternode has open will lead to the the DC null-routing traffic to that box, typically for 6 hours whilst they wait for the attack to stop. Mitigating this is an extremely difficult and expensive operation for each masternode to individually undertake, and not all DCs will even be able to provide DDoS mitigation at this level. An unsophisticated attacker using extremely traditional tools can knock all of the masternodes off the network except those they control. This is a threat to anonymity.
Incidentally, the other problem with masternodes that nobody seems to have thought of is that the limited number of them will mean they're in direct competition with each other. It is in a masternode operator's financial interests to make life difficult for the rest of them - DDoS attacks, reporting the box to the datacenter, anything that can knock a single competitor off the masternode network means more fees for the remaining masternodes. This is different to PoW mining where, for instance, knocking the pools offline doesn't mean you'll get more transaction fees, as miners always have backup pools. I'm not sure how sustainable this is as a system if it unmistakably pitches operators against each other to fight for fees. Given the cost and capital required to own a masternode, it's appreciable that this will happen as a natural result of wanting to maximise masternode profits.
There are two things that concern me:
1. Outputs can still be linked to addresses. If you send 20 DRK and it sends all these other outputs along with it to obfuscate, the 20 DRK still ends up in someone's address. That this can be observed on the blockchain means that analysis is easy, and we all know how often people leak addresses associated with their wallet (eg. posting it up for giveaways etc. etc.) This is an immutable problem in any Bitcoin-forked cryptocurrency that exists, as the solution (stealth addresses computed w/random data) has to be enforced for every transaction from the genesis block. If you enforce it halfway through you're stuck with old outputs that don't use stealth addresses, which makes it exceedingly complex to ensure the anonymityset is not at-risk.
2. Masternodes are an Achilles' heel. Let us say that there are 10 000 masternodes on the network. Their IP addresses and the port they operate on is, by necessity, known to the network. Let's assume that an attacker controls 5 masternodes of the 10 000. Let's also assume that each of the masternodes on the network is on a dedicated server (none of them use a VPS, because a VPS could be trivially owned by the host operating system) and each of these servers is on a 1gbps unmetered, dedicated port (clearly not the case right now, but I'm talking about a future time). How hard would it be for an attacker to knock the other 9995 masternodes off the network, leaving theirs as the only accessible masternodes (and thus not only earning them all the fees, but giving them perfect insight into transactions moving within their controlled group)? Well, NTP amplification attacks have let attackers launch 400Gbps attacks against a single machine from a sole 2mbps connection. SNMP has a theoretical 650x amplification factor. All an attacker needs to do is max out the unmetered port in an obvious attack, and the datacenter will have to react. Even straight up LOIC-style / botnet SYN floods to the port that the masternode has open will lead to the the DC null-routing traffic to that box, typically for 6 hours whilst they wait for the attack to stop. Mitigating this is an extremely difficult and expensive operation for each masternode to individually undertake, and not all DCs will even be able to provide DDoS mitigation at this level. An unsophisticated attacker using extremely traditional tools can knock all of the masternodes off the network except those they control. This is a threat to anonymity.
Incidentally, the other problem with masternodes that nobody seems to have thought of is that the limited number of them will mean they're in direct competition with each other. It is in a masternode operator's financial interests to make life difficult for the rest of them - DDoS attacks, reporting the box to the datacenter, anything that can knock a single competitor off the masternode network means more fees for the remaining masternodes. This is different to PoW mining where, for instance, knocking the pools offline doesn't mean you'll get more transaction fees, as miners always have backup pools. I'm not sure how sustainable this is as a system if it unmistakably pitches operators against each other to fight for fees. Given the cost and capital required to own a masternode, it's appreciable that this will happen as a natural result of wanting to maximise masternode profits.
