Using Litecoin To Protect Bitcoin Versus 51% Attacks - By Casascius

[CoinHoarder]

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.
 

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.

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.

[jonald_fyookball]

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.
 

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.

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.

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?

[QuestionAuthority]

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

[iluvpie60]

Mike Caldwell (Casascius) proposed an idea in the ALT coin subforums last year which I feel could be revisited. It is something that could help Bitcoin and Litecoin both by protecting Bitcoin and giving Litecoin more intrinsic value at the same time. He didn't receive a lot of good feedback, but Litecoin wasn't on a 6 month downtrend at that time, so I feel they may be more apt to it nowadays. This would make Bitcoin more secure, and I propose adding another chain to protect Litecoin down the road adding 3 layers of protection from different mining hardware. As long as the 3rd, 4th, etc... coins were PoW with different hashing algorithms than the coins already in the chain, it can exponentially add protection to 51% attacks by making someone that wanted to do one have to buy/develop SHA256, Scrypt, <insert coin here since we all know ASIC proof algorithms don't really exist.. or at least if they do it is buried in the ALT subforum and it isn't general public knowledge yet.> ASICs. There is no reason why this had to be used with only ASICs, you could use coins with algorithms that can only be mined currently on GPUs/CPUs/FPGAs/Etc.

I hope you guys are open to implementing this idea, as I think it is a great one. One of the best solutions to protecting against 51% attacks that doesn't seem like it would be too hard to implement.

I will quote Mikes' post here: https://bitcointalk.org/index.php?topic=176556.0

Litecoiners: Idea to make Litecoin importance skyrocket in Bitcoin ecosystem
Today at 07:20:47 PM
 #1
Quick rant: I have always viewed Litecoin as a detraction from Bitcoin and have refused to make mass quantities of physical Litecoins as a result.  I have viewed Litecoin as nothing more than a hedge against Bitcoin seeing a 51% attack due to choice of SHA256 as an algorithm.

But:  I believe I have thought of an idea that would make Litecoin far more important and relevant in the Bitcoin/cryptocurrency ecosystem, by being as ready in wait as possible in case Bitcoin really does experience a 51% attack.

In a nutshell, I view a Bitcoin 51% attack as eventually possible, for one reason:  ASIC production efficiency scales far more than linearly with the amount of money an actor is willing to put into it; a bad actor with $1 billion to 51%-attack Bitcoin with its own custom ASICs will be far more than ten times as effective than ten bad actors with $100 million.

Anyway: here is the idea:  Add a mandatory merge-mining feature to Litecoin so that it is always "merge-mining" Bitcoins, just for pretend, in hopes that one day Bitcoin will have the option of "let's subscribe to the Litecoin chain" (as a secondary means of block validation) as a way to resolve a future 51% attack on Bitcoin's SHA256-based chain.

Here is sort of how it would work:

1. Add a new requirement to the Litecoin chain such that a valid Litecoin block must contain either a record of the most recent Bitcoin block header hash, or a repeat of the hash found in the prior Litecoin block (with a limit of repetitions).  Litecoin blocks that contain outdated Bitcoin intelligence should be disfavored by nodes capable of detecting that.  Further impose the requirement that Bitcoin block headers must be represented contiguously in the Litecoin chain - Bitcoin blocks cannot be skipped (which shouldn't be a problem, when Litecoin blocks happen 4x as often as Bitcoin)
2. In the event there is an active Bitcoin block chain fork, the requirement is loosened such that the Bitcoin block header hash requirement can be satisfied by any leg of the chain, not just the one Bitcoin considers valid.
3. Add a feature to Litecoin clients that allow Litecoin users to decide to prefer or not-prefer branches of a Bitcoin fork while one is in progress.  The default for this should always favor the Bitcoin leg with the most longevity, and should disfavor long chains that suddenly appear to replace a large amount of the known Bitcoin block chain.  The user/miner/pool-op should always have an easy way to have the final say, such as by pasting in a preformatted message either exiling or checkpointing Bitcoin blocks.

Anticipated benefits:

1. Bitcoin users would have a ready made remedy to a 51% attack that they can switch to:  Bitcoin users can simply add the requirement that if a Bitcoin block header hash makes it into the Litecoin chain, that its proof of work should be given a bonus.  Litecoin community could create and maintain pulls to the Satoshi client that cause it to subscribe to the Litecoin chain and incorporate it as intelligence toward block validation and resolving block chain forks.
2.  Bitcoin would have an easy way to add an emergency upper bound to block creation, just in case an enormous amount of power suddenly appeared.  By turning on an optional must-appear-in-Litecoin requirement, the Bitcoin community could switch on an upper bound of 1 block per 2.5 minutes if it was deemed necessary.
3. Litecoin would be seen as far more important than a wannabe bitcoin knockoff without added value by those who see it that way.
4. Bitcoin's blockchain would be re-democratized to CPU/GPU users without forcing the Bitcoin community to switch to scrypt, they'd have more decentralized influence on bitcoin than those with the means to buy/make ASICs
5. The legitimacy of Litecoins would increase greatly - people would see the value of Litecoins in their role of protecting Bitcoin, and would potentially vote for the longevity of Litecoin by offering to accept LTC for goods and services, thereby increasing their value.
6. I'd start making Casascius Litecoins if you guys did this and did it well.

I'd call the concept "marriage-mining".  By doing something like this, LTC gives a nod to BTC's importance while adding synergistic value to BTC that LTC can benefit from by association.

I have brought it up in the Litecoin forums here: https://bitcointalk.org/index.php?topic=176556.0

I am interested to hear Bitcoiners opinions about it as well. I initially didn't like the idea, but towards the end of the thread on Bitcointalk I realized it could be a very good thing for BOTH Bitcoin and Litecoin. I've been really hard on Litecoin lately trying to get them to up their game, I am hopeful that if the Bitcoin community wanted this 51% protection that they would be willing to make it happen.

Won't happen. This isn't the place to do this. Basically, all ideas on here are not ideas that are incorporated into any changes towards BTC. This whole forum really is seeming pretty pointless more and more. I have no idea how there are people on here that have accounts that are years old. There is nothing to talk about, its always the same, scams, hacks, loss, gain, loss, gain, loss, opinions, and no one does anything about anything.

Bitcoin community has been broken for a long time and this "free market" you think you have is a joke, its all manipulated by bad actors in exchanges.

[ElectricMucus]

Won't happen. This isn't the place to do this. Basically, all ideas on here are not ideas that are incorporated into any changes towards BTC. This whole forum really is seeming pretty pointless more and more. I have no idea how there are people on here that have accounts that are years old. There is nothing to talk about, its always the same, scams, hacks, loss, gain, loss, gain, loss, opinions, and no one does anything about anything.

Bitcoin community has been broken for a long time and this "free market" you think you have is a joke, its all manipulated by bad actors in exchanges.

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.

[jonald_fyookball]

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?

[coblee]

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.

[smoothie]

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.

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.

[coblee]

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.

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.

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.