Topic: Using Litecoin To Protect Bitcoin Versus 51% Attacks - By Casascius (Read 2957 times)

You would do this with a miner vote. Basically implement this in the new clients. And have it in code such that when 95%+ of blocks mined in the last X blocks have this bitcoin hash data, then miners will enforce that every single block from then on must include bitcoin hash data. So this could take a long time (or never) but it will be relatively safe to do because when the fork happens, the majority of the miners are already running the latest code. And the minority would realize that they are on the wrong fork fairly quickly and would have to run the new code. Non-miners would be unaffected.

But like I've said, there's no good reason for miners to put in the extra effort to include bitcoin block data.

Wouldn't miners running older Litecoin clients (if this was implemented in a new Litecoin release) be relaying the wrong information and not keeping a complete and correct ledger for Bitcoin?

I wonder what the implications of miners/users would be who do not upgrade their clients. Assuming a fork isn't required, if a miner doesn't upgrade are they now mining on a different chain? If not, wouldn't their blocks they create not be complete as it would not have the Bitcoin information?

I can see upgraded clients rejecting the blocks created by miners using the older clients as they would be missing the Bitcoin information that is required to be stored in the block that was created.

The reason why this idea did not take off originally was because people think that there was zero benefit to Litecoin and possibly no benefit to Bitcoin either. To do this, Litecoin miners have to maintain both the Litecoin blockchain and the Bitcoin blockchain. It will also require a hard fork on Litecoin for this to work. It's basically Litecoin holding on to a lifevest for Bitcoin in the rare case that Bitcoin will need it and use it.

It's an interesting idea. I will spend some time to think about it more and see if doing this without a hard fork is possible. You basically have to somehow create incentives for Litecoin miners to also keep track of the Bitcoin blockchain. It may be as simple as checking a few bitcoin block explorers, but why would miners want to do that for no benefit... unless they are forced to by a hard fork.

I have an idea how this could possibly work.

You create an altcoin that has a kind of merge mining with Bitcoin.
In order to solve the altcoin's blocks, you would have to solve
the most recent block on the Bitcoin blockchain, albeit at a lower difficulty
level, PLUS a block on the alt chain.

By doing this, you would force mining power to be used on the Bitcoin
blockchain.  Sometimes, you would actually solve a Bitcoin block,
but overall you would be contributing hashing power to the Bitcoin
network, while participating in a secondary market (the altcoin).

Has this been tried before?

Straight on, this would be a good idea but it isn't gonna happen because of the things you mentioned.


I'm still here because the scams, hacks, loss, gain, loss, gain, loss, opinions are very entertaining to watch and laugh at. I've gone from thinking Bitcoin as a pretty cool idea to one of the dumbest shit on the Internet.

How are you going to protect the chosen altcoin from the Eligius pool. I not sure you will get LukeJr's support for this idea. lol

I'm not saying someone can kill litecoin easily.
I think you are missing my point.

Longest-chain-wins rule works to create consensus
in a distributed network because of its simplicity.

If you have 2 separate networks and they both
must "approve" a chain, then what happens if
one approves it and the other doesn't?

This is why Bitcoin should protect Litecoin using the same method, that way an attacker can't just hit the Bitcoin or Litecoin network separately. They would have to hit them both at the same time. Even without this protection, Litecoin is reasonably secure. I mean.. no one has been able to 51% it yet to my knowledge. You are acting like someone could easily kill Litecoin even without this implemented (like right now), which is a bit of an exaggeration as it would take a lot of money, power, and mining equipment.

As long as pools are reaching close to 50% (recently ghash.io on Bitcoin and coinotron on Litecoin), then both Bitcoin and Litecoin are insecure to 51% attacks. They may not have malicious intent, but if the pool server is hacked the hacker may not be so nice, or someone could gain physical access to the servers (IE. a government or data center employee.) Something needs to be done about this, and I feel like the solution proposed is better than the current non-solution. People like larger pools because they produce more steady payouts, so it's a catch 22 and Bitcoin/Litecoin will constantly face these security scares until the problem is fixed on the protocol level.

It's not necessarily a question of cooperation.

The problem can be reduced to logical operators: AND vs. OR.

Do you require longest chain AND a litecoin component?
or is it longest chain OR a litecoin component.

The OR solution is clearly bad, as it throws Bitcoin
security out the window, as we just discussed.

However, the AND solution might be too constraining.
If an attacker were to just hit the litecoin network,
it could prevent consensus, causing split chains or
blocks to be unsolved.

I just want this idea to be given a fair chance without politics getting in the way. If it is indeed a good solution to 51% attacks, then I don't feel it should be brushed aside because of our feelings towards Bitcoin (in case of Litecoiners) or Litecoin (in case of Bitcoiners.)

The 51% attack problem is not really easy to solve otherwise it would have been done already. We need to be proactive and if there is a solution such as this that someone has already proposed and makes the least bit of sense, then I feel like we should give it more attention. I'm more interested in the technicalities of this, how it could be implemented, and whether or not it will require a hard fork, rather than people's opinion on Litecoin or Bitcoin.

As I said, this method could be used on a different coin other than Litecoin, but Litecoin is in my opinion the logical choice due to the stability of its network and Scrypt ASICs making it one of the strongest PoW ALT coins. It may be a good idea to add a 3rd link to the chain such as a PoS coin... the attacker would have to 51% Bitcoin and Litecoin, and then gain majority stake in the PoS coin. It should be made so that if one link in the chain breaks all the others will be fine. I think there are a lot of ways this could be implemented.

Bitcoin is in the process of becoming the mainstream alternative to classic banking and payments. The general public is confused enough about crypto currencies as it is and altcoins aren't helping that perception. I've never believed that crap about Litecoins silver to Bitcoins gold. That's like saying the USA needs to have Pesos and Dollars to pay for different items. That's total bullshit. Altcoins are pulling users away from adopting Bitcoin and more importantly using Bitcoin. They create an unnecessary confusion when the uninitiated look at Bitcoin. It already looks like a list of game money (WoW gold, Bitcoin, Linden, Litecoin, Zeevex, Doge). I have pumped and dumped my share of alts and made a tidy sum doing it. When Litecoin first came out I was mining Bitcoin on GPUs and Litecoin on the idle processors of a dozen computers. Alts can be money makers like a Ponzi can be a money maker.

I don't want to require the survival of any altcoin because Bitcoin is tied to it. I think if Bitcoins problems are addressed by the dev team it will be the survivor because it has a head start. All of the alts will die a slow death while Overstock and Expedia are still taking Bitcoin. There must be another solution to PoW.

That's why it requires cooperation in between the Bitcoin and Litecoin development team. Bitcoin should protect Litecoin in the same way. Otherwise, you could add a 3rd coin to the chain making all coins even harder to attack.

Anyways, according to one of the most knowledgeable replies I've received thus far is that this can be done without a hard fork, and it makes it even harder to attack the Litecoin block chain in another way not mentioned in the OP:

I still don't think it would work... all you're doing in essence is relegating the consensus mechanism over to the litecoin network, which could be attacked more cheaply than Bitcoin.

I see where you are going. This is what Mike proposed in that case:


I feel like this may be able to be improved upon if a lot of people thought about it. Do you see a glaring issue in the idea? The way it was stated may not be the best way to implement it, but the idea seems like it could work.

The main chain would be quite long compared to the attacker's chain, so it seems like the client could pick up on which blocks are valid and invalid by comparing the size of the chains.

Yes, BUT the attack on Bitcoin would be much much cheaper if all you had to do was create a block
and your chain didn't have to be longer than the networks'. 

Yes I agree.


This I disagree with though, because someone would need to attack both the Litecoin AND Bitcoin network at the same time. Bitcoin could add in the same checks for Litecoin, so in order to attack Litecoin you'd have to attack Bitcoin too. This would increase security of both coins if implemented properly.

You do realize Litecoin has ASICs now, and the hash power has been exponentially growing for the past 6 months? It is not what I would call easy to 51% the Litecoin network at the moment. If you simply looked at the hash speed (515 Gh), it may seem like that is small compared to Bitcoin. However, you need to take into account that Scrypt is much less efficient than SHA256. You would need to develop/buy Scrypt and SHA256 ASICs to 51% attack the Bitcoin or Litecoin network, making an attack much more expensive. Therefore making it much harder to attack.

Yes, it is different from the way Bitcoin has resolved these issues in the past, but that doesn't automatically make it less secure.

currently, if there is a fork, consensus is reached by using the longest chain rule.
a doublespend attack means you are secretly mining a separate chain that has to be
longer than the main chain.  to do that is very expensive requiring lots of hashing power.

this proposal says to get rid of that scheme and use a different one involving litecoin.
and litecoin requires much less hashing power.

No, I don't understand your point. Why specifically would it make it much easier to attack? I think it would do the opposite.

I don't think so.

It says this:

.

Do you see why this doesn't make any sense?  You're messing with one of the key parts of the Bitcoin system and actually making it much easier to attack.