Recently DASH became immune to 51% mining attacks which is huge news for Dash fans across the globe, concerning how big of an issue this kind of attack poses to any given blockchain.


The Bitcoin blockchain has never been hijacked in its ten year existence, but Proof of Work (PoW) cryptocurrencies, like Bitcoin and others, are vulnerable to what is called a 51% attack, which is when a single entity, like a malicious miner takes over more than 51% of the mining hash rate. This vulnerability is constantly there and if nothing else it does create FUD in the industry.


 As a result, anyone who comes up with some system to mitigate this risk will certainly go a long way to securing the network from potential thieves as well as allaying any concerns among those wishing to enter the market.

 And it looks like Dash have indeed come up with just such a solution. 

<center>![](https://cdn.steemitimages.com/DQmSgz3FRsHbpZnqJSHKi4m5JZ85GWBrXpCFy1KZcxLJUJg/dash-immune-to-51-percent-mining-attack.png)
[source](https://www.google.com/search?q=dash+immune+to+51+attack&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj_neuf56DjAhVrlIsKHcx1BCMQ_AUIECgB&biw=1536&bih=723#imgrc=0SGcr7DsNYfJ5M:)</center>


### Proof of Work – the original foundation of cryptocurrency via mining
Although not easy, it is theoretically possible for a single miner or a pool of miners to group together and take over more than half the total mining power of a blockchain of any PoW cryptocurrency, of which there are several, Bitcoin being the original. [Here](https://cryptoslate.com/cryptos/proof-of-work/) you can see a list of 524 coins that are all PoW, including BTC ETH LTC BCH XMR ZEC and one which has just come up with the solution to this vulnerability in the system, namely DASH.
 

### What is a 51% mining attack?
There are usually many miners either individually or in pools anywhere in the world simultaneously mining Bitcoin or any of the other cryptos via PoW but if one of them is able to gain more hash power than all of the other miners combined, then s/he will have acquired 51% of the total hash power and will then be able to overrule all the blocks from all the other miners if so desired.

 They can then simply selfishly mine new blocks on top of their own. If done publicly others will notice the extra orphaned blocks, but it can be done privately in a secret chain which is published hours or days later, leaving the network to think all is fine and simply reorganizing itself accordingly.

 At this point, the malicious miner could secretly mine conflicting transactions on their own chain that sends coins published on the original chain back to themselves. 


### Honesty is the assumed policy
These kinds of 51% mining attacks are not thought to be likely because PoW relies on the principle that honesty is more profitable than malicious or selfish activity among miners. This is of course based on the premise that miners are rational people to begin with, and if some malicious activity was detected on the blockchain then the rest of the miners would outvote it with their higher hash power.

 That’s as long as new tech in ASIC mining equipment isn’t invented and kept hidden somewhere, like China, and used without the rest of the world’s miners becoming aware of it in time. China already has some of the largest mining pools in the world and if say two of those giant mining pools got together, they could really become a threat. 

And Chinese business ethic is known to far out-value profit above honesty.
 

#### Bitcoin Cash as an example of a weak blockchain
One cryptocurrency that has already shown vulnerability to 51% attack is Bitcoin Cash. It also uses the SHA256D protocol, just like Bitcoin but it has less than 10% of the hashing power that Bitcoin has. And when you don’t have the majority of available hash power for your algorithm, then you are always at risk of being attacked by selfish miners.


 In the recent “hash wars” seen earlier this year in Bitcoin Cash, when it split into two via the hard fork, multiple entities joined forces to enact the breakaway and really threatened the original network significantly, creating huge amounts of FUD, not only in BCH and its blockchain but in the very concept of PoW itself, despite not actually enacting a 51% attack as such.

 The coin nevertheless got delisted or had its transactions halted on some exchanges and attracted loads of negativity toward itself (thank you Craig Faketoshi). The entire market took a dip around that time, possibly based on all the FUD over a potential 51% attack.


#### Dash to the rescue 
Now there is a solution for all PoW blockchains, thanks to DASH coming out with Long Living Masternode Quorums (LLMQs) which allows for the implementation of a new system of protection against such 51% attacks from malicious miners. You can check out their [Github](https://github.com/dashpay/dips/blob/master/dip-0008.md) for more detail The security measure itself is called ChainLocks, which verifies the first block that is seen extending the active chain. When the majority of members involved in the mining process agree on the same block, they can create a P2P (CLSIG) message to be propagated to all nodes in the network. So it’s based on a form of consensus and has been proven to be failsafe, as there can only be one valid confirmation message or none.


#### ChainLocks for protection
There is obviously a lot more detail which those who are more tech savvy and seriously interested in can find at the Github mentioned above. Basically it means that once a valid consensus message is received by a node, all other blocks and their descendants which are not part of the longest chain are rejected. It’s quick, easy and unambiguous and prevents any reorganizations of the blockchain below the validated block.


##### Implications for the user
The great result of this feature is that for normal users of Dash for commerce or trade, buying of goods etc, transactions can be considered fully confirmed after the first on-chain confirmation inside a block that is protected by ChainLocks. As a result transactions won’t vanish from the chain because reorganization is not possible, and so we don’t need to wait for the usual six or more confirmations for the transaction to be considered secure. 

It also obviously removes all incentive from the miners to cause chain reorganizations, which is the root of potential secret attack by withheld longer chains that are subsequently released. With ChainLocks miners are incentivized to publish every block immediately. 


##### PoW now validated
It appears as if all the concern about PoW being a lesser system than say Proof of Stake (PoS) due to its vulnerabilities can now be laid to rest, thanks to DASH’s ChainLock addition. The longest chain rule is still maintained, although it can be overridden by a valid CLSIG message, but then only the members of the responsible LLMQ are fully actually following the longest chain because they are the ones creating the CLSIG message via consensus.


 And since the CLSIG message can only be created if enough LLMQ members reach consensus, the very presence of the CLSIG message serves as proof that the particular block that is referenced is actually the block resulting in the longest chain.

##### Trust in a trustless system
The ChainLocks protocol does rely on trusting the CLSIG messages and the masternode network, but DASH sees this as an acceptable trade-off, since we were already assuming that the masternode network is honest, which is the same rationale applied originally to the miners in the PoW system. 


The difference is that with Chainlocks in place, both miners and masternodes would have to acquire a 51% take-over on both layers and then collude if they wanted to succeed in hijacking the blockchain. And even then malicious attackers would still not be able to cause very deep reorganizations because the previous CLSIG messages cannot be invalidated. 

So ultimately no consensus rules are broken in this system and all nodes must fully verify a block before accepting it, thus preventing the double spending problem.


##### Can other coins use ChainBlocks?
This system is based on a “Sybil” protected network of semi-trusted nodes so any other coin would need to have that in place to use the ChainLocks facility. With DASH, the masternode network is protected from Sybil attack by requiring each node to have 1000 DASH collateral, which makes it economically impractical to perform a Sybil attack. A potential attacker would have to buy at least 60% of all masternodes to have a chance of success.

 This protection layer against Sybil attack is still highly undervalued and is a main prerequisite for ChainLocks to function. In time even more innovative features can be implemented safely making DASH even faster, more secure and user-friendly.


 Let’s see who can keep up with that.


<center>![runi reveal.gif](https://cdn.steemitimages.com/DQmVRBCZfYpkHjWXQdbirDgeFJbRU6YqCFN8fvmDMFm8GhT/runi%20reveal.gif)</center>