Bitcoin Forum

Blockchain is a new kind of database - block or records connected to another block. That's the simplest explanation. However, I want to ask the hard question.

What are the limitations of blockchain? I know this is a really good innovation and I highly support it, not because I join the bandwagon, but because bitcoin will not exist if not because of it.... But I want to have a better understanding of the blockchain (in layman's terms please) if I want to get really serious about cryptocurrency and ICOs. My second question is, what are the things experts do to improve blockchain?

This is the Bitcoin board so I'll be speaking about the Bitcoin blockchain....

The first and most evident "limitation' of blockchains is scalability.
Public blockchains are very hard to scale especially on-chain.
This is because of the way bitcoin achieves consensus; most nodes must verify a transaction (or block) is valid.
If the block size is too high then a lot of nodes will be cut off and this leaves the power of the network in the hands of a few people which leads to centralisation.
Also, if the block size is too low then obviously a lot of transactions won't be able to fit and this leads to high fees during high thoroughput periods as people will pay more for their transaction to be mined.

The blockchain works great for currency systems, and to an extent, smart contracts (provided they are not needlessly complex, or else you risk losing all stored funds to a bug/hack/unintentional loophole). Alas, there are not many other practical uses for the blockchain, owing to the fact that the very premise of the blockchain requires distributed nodes (which usually requires monetary incentive or a token), and it also requires the transparency of data. Now, it's very fun to think of big banks and companies using the blockchain for all of their transaction, but if this was implemented in the real world, the idea falls flat on its face. Why? Because no bank/company in their right mind would reveal all their information publicly, no bank/company in their right mind would let third (or even second) parties control their nodes. They would implement what is commonly known as a private blockchain. A private blockchain is also known as a database.

There are many limitation of blockchains like: Complexity, Network size, Transaction costs, network speed, Human error, Unavoidable security flaw and  Politics. It has made cryptography more mainstream, but the highly specialized industry is chock-full of jargon. Thankfully, there are several efforts at providing glossaries and indexes that are thorough and easy to understand.

scalability. if this canbe solved, then crypto will really take off from where it is now

Fragmentation.

Blockchain is based on a peer to peer system. So each peer/node have the freedom to choose which “version” of the software to run. This makes it difficult to implement significant changes to the codebase because each peer may have different views on the changes.

As to private chains, I don’t see a point for it. Without the hashpower backing it, it would be the same as a normal database. As is the case with most ICOs.

Bitcoin's solid security brought by the cryptography-based (public ledger) system known as the Blockchain have a lot of limitations
but not one of these (bold and colored):
Seriously, how can an automated public ledger produce human errors? What you wrote were typical human handling errors that are not exclusive and caused by the blockchain.

Anyways, things that I'm noticing are:
[1] The Full Node's increasing file size, the current 145GB+ of Data may be easy to store in any HDD/SSD (not even mentioning the synchronization speed), but somewhere in the future it can grow up to 1TB that can be inaccessible for some.
This can lead to standard full node users to use 3rd party clients, nodes could be exclusively owned by huge groups or companies due to its inaccessible size, might result in less nodes, more centralization.
There are couple of possible solutions to this, in the future, developers might find a solution to this even before the full node reach that level.
Let's say, start by not increasing the block size.

[2] The 51% attack. Today's hashing power might be phenominal, even with the unethical mining system we have now known as pools, a 51% attack is nearly impossible.
But when the 21m BTC supply was mined, miners will surely shift to a more mining-profitable coin that can lead to a lower Hashing power.
With that, one of those huge pools can easily gain more than half of the mining operation, it's up to them whether they use that advantage to help or destroy btc, things will differ depending on our view of digital currencies at that time.

It's easy to assume that new technologies can pave a road to a better future, yes it can, but all had gone to a phase that required us to deal with its own limitations.

I'd argue that this is both a boon and a bane.

Giving nodes the freedom to run different, possibly competing versions of the protocol provides an unprecedented form of autonomy to users. It keeps developers in check to not stray too far from what the users want and enables users to fork off should they perceive the original vision of a blockchain project to be compromised -- which is pretty much what happened with the Bitcoin Cash hardfork.

Of course it makes updates and reaching consensus regarding upgrades difficult, however I'd argue it's a price worth paying for making sure that no single entity gains too much power over a blockchain.



One of the side-effects of the rise of ASICs has been that Bitcoin is sharing its PoW scheme with only a handful of coins, signifcantly reducing the number of possible targets to alternatively point hashing power at. Nonetheless it is of course impossible to predict how the world and cryptocurrencies will look like a 100 years from now, given the latter still exist.

It’s an oversimplified explanation.  The blockchain forms a Merkle chain of unalterable history, whereby correct knowledge of the present can be used to verify correct knowledge of the past.  Adding a Hashcash-style POW function for transaction ordering, it becomes a Byzantine fault-tolerant distributed database with no central authority or trusted “supernodes”.  That’s the simplest explanation I can provide in two sentences.


Solving the problem of creating a Byzantine fault-tolerant distributed database with no central authority was a work of genius by Satoshi.  This required design trade-offs; and as a result:  The blockchain may well be the world’s most inefficient database; and it has very limited scalability.  These are not problems, because higher-layer solutions (Lightning Network) can use the blockchain as a foundation.

Thus, yes:


A trusted database system can always beat a blockchain-style system hands down for performance.  But then, the best currency you could build would be Paypal 2.0.  Whereas Bitcoin is a trustless, permissionless currency which nobody controls.


ICOs are scams, ipso facto.  Avoid.


To improve Bitcoin’s blockchain and the more efficient usage thereof, a few examples are:  Segwit (done), Schnorr signature (in development), MAST (in development).

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Aside:  Complexity is not the issue with smart contracts:  Correctness is.  To see some of the advanced research work being done to potentially bring powerful, mathematically provable smart contracts to Bitcoin, read the paper on Simplicity (PDF) (https://blockstream.com/simplicity.pdf).

(That’s not on the topic of the blockchain itself; but it’s no secret I despise the centrally controlled exploding clown car amateur show of Ethereum, and I do so look forward to the prospect of things being done right for Bitcoin.)


Transparency of data is not required.  Zerocoin (the concept) and Zcash (the existing currency) use zero-knowledge proofs such that all that is revealed is, “a valid transaction occurred in which outputs did not exceed valid inputs”.  There is other work being done to obscure information, such as Confidential Transactions for Bitcoin.


There was a collaboration between JPMorgan and Zcash to produce a zero-knowledge proof implementation for banking use.  The precise reason was that big banks do not want to reveal confidential transaction information to competitors seeking business intelligence.  Note:  I am in no way, shape, or form endorsing JPMorgan’s Quorum, or anything whatsoever to do with JPMorgan, a/k/a Evilbank of Evilbanks.  I am simply relating some interesting facts which pertain to what you said.


This is not a valid concern.  The important part is your node; and nobody controls your node in Bitcoin.


A “private blockchain” is also known as a hyped-up dog and pony show based on buzzwords and not engineering.  An ordinary ACID database is inconstestibly superior for 90+% of use cases for so-called “private blockchains”; and for 9+%, there exist other network database solutions which will be far more efficient.  There are only a few corner cases I can imagine even in my wildest fantasies whereby a “private blockchain” might make sense.  Adding a central authority instantly removes some extreme engineering challenges.

A “private blockchain” which amounts to Paypal 2.0 will be slower and costlier than Paypal 1.0.  Why bother?

(Aside:  I mostly disagree with your post, but it was cogent.  Also, it pointed out something I am well aware of, but most Bitcoiners don’t realize:  Big banks and huge corporations do not want to reveal their private info in a global public ledger.  Sure, they want to rape your privacy—but they jealously guard their own.  Thanks for bringing that up.  +1.)

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Not a limitation of the blockchain.  Rather, a product of corruption at the wetware [human] layer—resulting in intentionally divisive disinformation campaigns.


Any advanced technology will involve jargon incomprehensible to those who have not studied it.  So...?

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Interesting angle.  But it is an issue with decentralized P2P systems, not the blockchain per se.

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That’s not a limitation of the blockchain per se, but rather, a security limitation of its design for using Hashcash-style POW for transaction ordering.

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And this is one facet of a very significant reason to not switch POW algorithms.  Thank you.

 ::) Hello I was able to browse the following list of weakpoints of Blockchain Technology (big thanks, credit goes to the author ROB BLASETTI from his article 5 Weak Points of Blockchain Technology   https://blockgeeks.com/public-blockchain/ );

 :)1. There is no customer protection on the blockchain.
=> Blockchain technology operates as a push-based settlement system. This means the individual holds power over the resource they want to verify on the blockchain. This could be cryptocurrency, certificate authentication, land titles, etc. The problem with this is if a transaction goes sour after it has already been verified on the blockchain, the only feasible way of returning the transaction is if the parties agree to reverse it. Using a centralized system like a bank. However, there is a procedure in place to be able to dispute trades after they are complete.
     Some trade technologies that settle on a blockchain have used an arbiter system to fix this problem, an example of this is the Open Bazaar P2P trade network. This way a trade occurs between two people, and one impartial moderator.

 :)2. Settlement on a blockchain is slow.
=> A cost of settling a transaction on the blockchain is that all the nodes in the network need to come to an agreement that the transaction is valid. This is a far slower process than having a bank verify your transaction in an instant.
     Transactions can be made instantaneously, however until the block in which the transaction is inserted in has been verified, it is classified is untrustworthy. In the time between a lodged transaction is made and when the block settles, a bad actor could launch fraudulent transactions to trick the network into what is known as a double-spend.
     A very exciting upcoming technology that could solve this problem is the lightning network. This solution acts as a layer 2 of blockchain technology; it can be applied to any public blockchain. It will enable instantly verified transactions for a fraction of the cost of today’s settlement.

 :)3. Miners can be selfish
=> The mining process on the blockchain is an innovation which uses game theory economics to incentivise people to commit computer power for securing the network for a profit. The down-side of this is generally miners won’t care about settling as many transactions as possible; they will make the most money by finding and verifying a block in the fastest way possible.
     This leads to a problem of miners finding empty blocks and validating. There is also another problem known as Selfish Mining, which is a situation where a miner or mining pool finds and validates a block and does not publish and distribute a valid solution to the rest of the network.

 :)4. The growing blockchain size
=> With every new block, a blockchain grows. This can be an issue because each node that is validating the network needs to store the entire history of the blockchain in order to be a participant. This is a hard enough problem with the bitcoin blockchain where the transaction size is only a few bytes, the total blockchain size as of January 2017 is 98GB. Given that at the same time in 2016 the size was 50GB, and the use of the blockchain is continuing to increase, this is a growing concern.
      One of the biggest debates in the bitcoin space is if the block size should be increased. If a blockchain has bigger blocks the blockchain size will increase faster, thus weeding out the solo miners eventually. This is a big issue because the health of a blockchain network is partially dependent on the amount of nodes in the network, and the spread of those nodes across the world. The counter argument for this issue is that with sufficient advancement of technology hard disk space will be very cheap in the future and will stay ahead of the blockchain size. The debate is ongoing.

 :)5. Eventually settlement on the blockchain will not be cheap
=> On any public blockchain, space in a block is a finite resource. Necessarily as the network is utilized more the amount of transactions that will want to settle in a block will exceed the storage capacity. Public blockchain networks have a solution built in for this which is that transactions with a higher miner fee attached will get precedence to be included in a block. This makes sense because the miners want to maximize their profit so that they will include transactions with the highest fees first.
     This is not a bug, but a feature. If it were free to settle on the blockchain, there would be far too many ways of attacking the blocks with dust transactions and clogging up the network. Originally the bitcoin blockchain had no block size limit; this was eventually set to 1MB to avoid a Sybil Attack on the network.

Thank you for this post. It's always mildly infuriating how people focus on the boring part of blockchains -- ie. the database aspect -- while completely ignoring the interesting part -- ie. achieving consensus.

Now one may argue about the up and downsides of PoW, but one thing should be clear to everybody -- a blockchain without a decentralized, permissionless, trustless way to reach consensus is only half the fun.



Customer protection is a legislative responsibility, not a technological one. If you use cash or Bitcoin to pay a law-abiding merchant they will still honor your rights as a customer. If you wire transfer money to a nigerian prince customer protection will do shit for you.



Traditional payment methods may seem instant, but behind the curtain settlement is way slower than Bitcoin's or that of other cryptocurrencies'.

Wire transfer / SEPA transactions can take 1-2 days to settle. Direct debit can take up to 14 days to settle. Credit cards / PayPal can take even longer.



Selfish mining is a potential attack on the network but an uneconomical one at that. Unlike mining empty blocks, it has nothing to do with mining incentives being misaligned.

Thanks for all of your answers! I am enjoying reading your replies and it gives me more realistic understanding about blockchain. At first, I thought that this technology will be the magic bullet to every technological problem. But now, I know that blockchain is not for everyone. But when used correctly according to its purpose and strength, it is indeed a formidable technology. For example, a pen was invented for transcribing and recording data on paper, but it is useless as a chopstick or to stab on something - sure, you can use it as that, but its full potential will not be realized. See the picture? I'm not saying that people should limit the use of blockchain, though. That's why we have developers. 

This is what people should be educated about: the pros and cons of everything, and to have a realistic and healthy expectation about blockchain and cryptocurrency.

Core developer gmaxwell is prophetic.  In one of the earliest posts to which I awarded merit, he wrote of how DHTs...


There is no such thing as a “magic bullet to every technological problem”.  Unlike DHTs, the blockchain is actually robust and secure (including Sybil-resistant) in the use case for which it is the right tool for the job.  The blockchain is a work of genius.  But it is still only the right tool for the right job.

Don’t believe the hype.  Ignore the buzzwords.  Know the facts—I am pleased that this thread has helped you do that.


Exactly.

This can be summed up by saying that blockchains are only useful for abstract information that benefits from being uncensorable, of which money and contracts are examples. Other examples I would include would be ID systems and data timestamping (Satoshi proved this in an inverted way by adding the famous "The Times 3.1.2009, Chancellor approves 2nd bailout" text to the genesis block, any data referenced in a blockchain can be verifiably proven to have existed at least after a verifiable time/date).



Don't you mean this is the reason not to be holding any coin using the PoW algo to which Bitcoin's PoW algo is switched?

Clickbait for hardcore Bitcoiners:

https://petertodd.org/2016/opentimestamps-announcement

https://opentimestamps.org/


No.  First off, the existing investment in ASIC hardware benefits Bitcoin security insofar as it locks miners into mining Bitcoin (or scamforks—hmmm).  If Bitcoin miners were forced to dump their existing investments in the trash and restart from scratch, they may very well decide to play the market with altcoins—especially since they might feel betrayed (and in the case of some of the better miners, they might have a point).  Moreover, the existing ASIC base provides a formidable hashpower which could not be rebuilt overnight.  Meanwhile, network would be relatively weak.  Lesser hashpower equals lesser resistance to anybody obtaining 25%/33%/51% of it.

There is a trade-off involved:  Mining is now much too centralized; and installed base obviously benefits incumbents.  But on the other hand, a switch would most benefit whomever could rapidly build out a new installed base.  That very well could be the same incumbents.

So as for what I meant.  As for what you said:

Any alt already using the hypothetical new Bitcoin POW would be potentially crushed out of existence, unless the new POW could be merge-mined (https://en.bitcoin.it/wiki/Merged_mining_specification).  Then, both blockchains would share a mutually beneficial symbiosis; and the existing alt would receive a security boost from the flood of new miners.  Of course, I don’t see great prospects for this unless the coins are not economic competitors; observe that Namecoin, inventor of merged mining, does not compete with Bitcoin as a currency.

Right. I'd like to think that tech like the above could be leveraged to create a database of author attribution (although I must stress: not the laughable "copyright" concept). It'd be a great way to promote the generalised use of cryptographic signing keys; anyone who believes their idea might be falsely attributed to someone else can submit a signed hash of their original works to a blockchain.



Eventually, kakistocracy could overwhelm Bitcoin. S2X only failed because not enough people are presently foolish enough to swallow stories about politically motivated emergency hard-forks to different consensus rules defined by a different dev team. At some point, the balance of fools running Bitcoin nodes could be right for that to happen. PoW change is the only possible way to fight that scenario.

Although I hope that won't be necessary, I can see how some kind of technological improvement in semiconductor fabrication could decentralise mining with SHA-2 PoW. I would also point out that it would be surprising to me if SHA-2 has infinite longevity, but maybe that's a long-term problem.



Yes, this is what I meant. Unless other cryptocurrencies using a hashing algorithm that Bitcoin uses have some in demand use-case that isn't duplicated by Bitcoin, then they're set to lose significant amounts of hashrate (assuming Bitcoin is still the dominant cryptocoin)

I think the most damage done to Bitcoin has been done by those that were promising challenging centralized payment methods such as VISA while doing it on-chain. This is a limitation of a blockchain that pretends to be decentralized. It's just going against physics basically.

The only way we can ever compete against a centralized system is via second layer solutions. Do we really need to?

I never saw the need for Bitcoin to be seen as a viable way to pay for your groceries when I understood the problems it had and how it was better suited as censorship resistant decentralized electronic gold of sorts. But maybe at this point we can't afford not being both, or at least attempting to be both. Is this possible? We'll have to find out. If LN is a success and on-chain transactions are still viable for "gold-tier" transactions, we will have both and this promise of "banking the unbanked" will actually become real, since some poor guy in Africa is better off with LN than with nothing else, the problem is again, if this will become a problem and make on-chain transactions non-viable at some point... again, we will need to find out.

Is transparency really a requirement? I believe the Bitcoin blockchain was only transparent because there was no one developing any implementation for Bitcoin that can mask the sender's address, the receiver's and the amounts at that time.

We do now.


Not only that. A real "blockchain" is inefficient and slow. It's better if they stop joining the bandwagon and use Bitcoin.

This is new info to me. Forgive my ignorance about quantum computers, but how will it be a huge threat to blockchain? i mean, i just can't see the point why blockchain will be vulnerable. I thought people are aiming to improve it?

There are a lot of threads on Bitcointalk about the threat of quantum computers on bitcoin.
http://lmgtfy.com/?q=quantum+site%3Abitcointalk.org

The gist of the matter is that quantum computers can break ECDSA which bitcoin uses for digital signatures and will be theoretically able to calculate private keys from public keys.
This is prevented by not reusing addresses because addresses are not public keys but a hash of them and quantum computing can't do anything with them. (An address's public keys are exposed whenever a transaction is made with that address)

However this is not a significant threat as quantum computing isn't that advanced yet, there are better easier targets than bitcoins (or other cryptocurrencies), and bitcoin can always move to a quantum resistant algorithm.

(Boldface is here added to question-begging.  Smart, well-informed people don’t have “so much fear” about quantum computers; thus, there is no “why”.  I have never beaten my wife; therefore, I have never stopped beating my wife.)


Yes, so very many threads.  Behold the power of Quantum FUD® (https://bitcointalk.org/index.php?topic=2561150.msg26900160#msg26900160), superposition of which is entangled across the forum!


Xynerise, you seem generally well-informed; but here, I think you are sorely mistaken in picking up an unfortunately popular meme.  Quoting one of my better Jr. Member posts from way back when, in the context of a thread about Bitcoin and quantum computers (bracketed clarification added):


Also apropos, in a distinct context (whereas FUD can only be distinct without difference):


Evidently, I am not the only one to be of the opinion that “hash public keys for quantum resistance” is a regrettable meme.  Quoting from discussion of Taproot (https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-January/015614.html) on bitcoin-dev, 2018-01-23 (https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-January/015620.html):

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As a general point about the strength of Bitcoin’s cryptographic security, from an adapted self-quote, I hereby formally posit the Nullian Flying Fire Hydrant Rule:


Please.  You don’t worry about being killed by a flying fire hydrant.  Whereas to be killed by a flying fire hydrant is not only possible, but astronomically more probable than any cryptographic break of Bitcoin security.

At some point, after the size of 2¹²⁸ is explained for the 2¹²⁷th time, anti-Botcoin FUDsters realize that FUDding Bitcoin security in the present just makes them look absurd.  So, they upgrade to Quantum FUD® technology:  Point to an uncertain future, oversimplify complex technological questions much debated by experts, and then beg the question of “why there is so much fear about the development of quantum computers”.

Practical, usable quantum computers do not exist.  Their present is fantasy, and their future is unknown.  Some experts are of the opinion that a practical quantum computer capable of useful computation may be impossible—scientifically, physically, mathematically impossible.

E.g., quoting from one of my Newbie-rank posts (https://bitcointalk.org/index.php?topic=2561150.msg26288168#msg26288168), q.v.; see also the ensuing discussion between myself and haltingprobability:


On that note, in closing, I will repeat in this Quantum FUD® context what I said more generally about Bitcoin’s public-key security (https://bitcointalk.org/index.php?topic=2859033.msg29345381#msg29345381):

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I think Xynerise concludes correctly:

At least this is comforting to know. As of the moment, I will put my trust on the people behind improving the security of bitcoin. Nothing is ever perfect, but the goal is to minimize the risks. That is why it is important to ask the difficult questions, while people are taking care to be balanced in opinion as well, so that unecessary fear is avoided. The reason why I didn't check out on quantum physics here in this forum is because I didn't think it was an issue for the blockchain until you opened it up.

Hi

  I know the block chain limitations

 1.Network error
 2.Network speed and size and transaction cost
 3.Human error
 4.unavoidable security flaw
 5.politics

Well it really depends on which implementation of the blockchain you are referring to, if you're looking at the bitcoin core blockchain one of the limitations is the block size of 1Mb, meaning only 1Mb of transactions can be included in the next discovered block, thereby limiting the total of number of transactions the network can process at once. Another limitation is the the ledger is publicly available, meaning that anybody can go and check your balance, your transaction history and who you've been dealing with, something that most people probably don't want probing into.

Although the blockchain is an emerging technology, all the technologies that make up the blockchain are the technology developed in the last century. Whether the dependent encryption algorithm can be deciphered with the development of the computer, can the data network synchronization be realized?

WRONG.  Bitcoin no longer has a block size limit.  Segwit replaces the block size limit with a block weight limit, set to 4000000 bytes (https://github.com/bitcoin/bitcoin/blob/1e65f0f3396d5d7eaa8e8dd3668dfa180b541c18/src/consensus/consensus.h#L14):


Perpetuating the obsolete notion of a 1MB block size limit is often part of wider disinformation against Bitcoin (https://bitcointalk.org/index.php?topic=2905590.msg29911450#msg29911450), and certainly feeds into it.

It is true that the block weight limit does constrict the transactional capacity of the network.  It is estimated that with full Segwit adoption and the types of transactions typically seen on the blockchain, blocks should average a bit more than 2MB in size.  Further scaling will be achieved by (0) off-chain vertical scaling by adding another layer, with Lightning Network, (1) on-chain efficiency improvements such as Schnorr signatures, and (2) what I call “horizontal scaling” with sidechains/Drivechains.  Lightning Network is already live and running, albeit still in its early stages; as it matures, its scaling effects will be huge.  N.b. that by taking transactions off-chain, it makes blockchain limitations less relevant.


This is true, although blockchain analysis is not quite so easy as you say.  Bitcoin is not anonymous (https://bitcointalk.org/index.php?topic=2527738.msg25825717#msg25825717).  Use appropriate technical measures to protect your privacy (https://bitcointalk.org/index.php?topic=2527738.msg25852987#msg25852987).

Yes splits it between two files giving a total of about 3.5meg but they did not need to mess thing up by
coming up with vbytes to muddy the waters and should stick with plain old bytes because we all know
what they are.

Someone posted about the signature not having to be tested by lazy miners looking for a bit more speed
because it is in a separate file but apart from that I am OK with Segwit but will never be OK with Lightning
and its banking hubs that like you say is taking shape and it's not looking like any mama & poppa type home
banking that I have ever seen before. https://lnmainnet.gaben.win/



   

Yep. I've read a lot about Segwit and the main detractors of Segwit are the miners because it cheapens the incentives they get through mining. But as someone who wanted to improve the blockchain, I am pro to it.

The data is written to the block chain, waiting at least 10 minutes, all nodes synchronize data, and more time is needed! Block chain transaction data is delayed.

The generation of blocks requires the miners to carry out numerous meaningless calculations, which are very energy-intensive.

All very fine but it won't scale as implemented by Bitcoin and hashing of hashes, well the credit has to go back to Bit-Torrent
for that one and I am yet to see anyone using a block-ledger (My invention) but i am sure someone will cotton on or were using
it long before I thought it up.

The solution to making the block-chain scale has been going off-block and we certainly have "supernodes" on that
as can be seen here https://lnmainnet.gaben.win/

Yes network chatter becomes a killer when you scale upwards and you need to have order which DAG addresses using
direction (Not that I fully understand DAG) and I have used sub-domains based on the public keys but in the end you have
to accept that you need something resembling a data center or the chatter and delays becomes unacceptable.

Block-Chain with most of its code being concerned with mining is not the answer and just works left to right (2D)
and it needs to work downwards too (3D) with what I call block-ledgers at the very least to record the transactions
but maybe one of the other alt-coins has a better solution but some of them are very difficult to understand.

 

There was a time when the Bitcoin blockchain and the Ethereum blockchain were filled with numerous transactions which lead to overflow of transactions in the memory pool. This became a problem as confirmation time was increased due to delay in confirmations and transaction fees were getting high due to this reason. Although now the memory pool is less occupied, it still is a bane as the same situation can occur again in the future. This is the only problem which needs to be rectifies in the blockchain. Other scalability issues are almost fixed with the implementation of Segwit.

In my opinion the limitations of the blockchain is transactions times and miner fees, a year or 2 agao bitcoin was not as popular as it is right now, as the price started to grow nad people started knowing about it it got popular and this affected the traffic control in the blockchain netowrk which was reflected on the trnasaction time nad miner fees which have reached high values, blockchain was not ready for a situation where a large amount of transactions can be sent and confirmed at the same time, and probably that is its biggest flaw.

No. As long as transactions remain unconfirmed in mempools, even if it concerns millions of transactions, they aren't 'filling' the blockchain. Transactions only 'fill' the blockchain once they are confirmed, and thus are no longer in any mempool. Otherwise Jihan & Co would have made sure the current blockchain would be a few terabyte in size already. :D

What scalability 'issues' has Segwit fixed according to you? Segwit itself isn't a problem solver at all when it comes to scalability, the second layer applications that will be built on top of Bitcoin will play the most important role in that regard. Segwit is basically just a first step that needs to be set in order to move further.

The blockchain is decentralized, and one of the meanings of decentralization is that there is no one person, or an institution is in a position of power, and no one has the final say. Any "decision/status/change, etc." requires participants to use a mechanism to achieve the same understanding, which is the limitation of the blockchain.

Reading through this thread, I am missing the positive developments. I mean, by the headline people get already distracted - ok, but you were explicitly asking about positive developments.

With many answers here I wrote up (unintentionally) something, which might answer your question, especially looking at the newer developments.

https://bitcointalk.org/index.php?topic=3074677.msg31895112#msg31895112

When re-reading the headline, I think it should be precisely this: „what is it in the mind of people, what makes them think, there are limitations in blockchain“  :D

Blockchain is not perfect and everything is this world have it own limit. However, I only know 2 limitations of blockchain network. (1) The limited total number of transactions that blockchain network can process per seconds. An Example bitcoin network can process 5transaction per second while Ethereum process 7 transaction per seconds. (2) The 51% attack.

I think the limitations are in scalability and security. That's if it's a decentralised blockchain. Although I think bitcoin is proving that it is possible.

The two most unavoidable limitations of blockchain will be its size and the transaction tax & speed .
When the market cap reaches to its highest extend it becomes unavoidable to overlook the shortcomings rising due to the network size . It gets filed and overloaded with the unconfirmed transactions . Moreover , that scenario leads to high transaction fees and its long delays.

I still havent got the meaning of blockchain means what are they and why are they even used?

Blockchain's limitation are known to its complexity because blockchain technology requires new vocabulary to installed. It is made of  cryptography codes, but there are some details provided by the internet about glossaries and indexes that are easy to understand for us to be familiar with it. Another thing is the human error, because if a blockchain is used as a database, the information will be inputted in the database must be a good quality. The data stored on a blockchain is not inborn safe or trustworthy, so if that would be the case it is obvious that you need to have a back up for those data that you're going to stored. Basically, blockchain technology is an undeniably master piece invention because it is a decentralized technology but still blockchain isn’t perfect. 

I think one of its limitations is that as bigger data are embedded into it, the larger the transaction fee and the slower it may process. Ofcourse, as more people indulge into that specific blockchain, more files and data will be stored leaving some of it unconfirmed. This delays transactions.

I think may be its the scalibilty but pardon me as i know not much about it. The term i just heard it from my friend :)

don't listen to friends,listen to nullius :)
you can read the topic and find many interesting things that can be called limitations of blockchain
all of them(or at least the majority of them) were discussed at length,plus some interesting insights into the most popular
misconceptions about quantum computers resistance,cryptography and fire hydrants

There are many drawbacks some of which are Network size, network speed but not human error as its an automated public ledger

Can't scalability issues be solved through a sidechain ?

I made my research about blockchains limitations and one of which is Human Error. Here it says,
If a blockchain is used as a database, the information going into the database needs to be of high quality. The data stored on a blockchain is not inherently trustworthy, so events need to be recorded accurately in the first place.

The phrase 'garbage in, garbage out' holds true in a blockchain system of record, just as with a centralized database.

Then, try your best to digest this: Wikipedia/Blockchain (https://en.wikipedia.org/wiki/Blockchain)

So you're saying that, if a monkey inputs a data into a blockchain-based database and the result was incorrect or an error, the problem came from the blockchain?
No, "human error" is not a blockchain limitation. If it was, Everything that involves human interaction has "human error" limitation.
Read this post from the first page: https://bitcointalk.org/index.php?topic=2981313.msg30676552#msg30676552 (https://bitcointalk.org/index.php?topic=2981313.msg30676552#msg30676552)

I think the biggest task we face is scaling without sacrificing any of the underlying privacy and security problems it done so well to solve