Bitcoin-NG and Byzcoin seem pretty promising IMO. The 2/3 computing power is required to rewrite the history of the blockchain, as only receiving enough approvals from the committee shall a block pass the verification. The problem of both solutions is that they depend too much on the reliability of the leader node. I'm working on a project that improves upon Bitcoin-NG's security and incentive issues.

Thanks for everyone's discussion. For the past few months, I've been researching on how improvements can be made to Bitcoin blockchain. It's undoubted that Bitcoin's scalability has become its Achilles Heel. Among the proposed solutions, I found Emin Gun Sirer's Bitcoin-Ng more promising. It separates proof-of-work and transaction validation processes into two blockchains. The proof-of-work and transaction validation are not much related, as proof-of-work's sole idea is calculating SHA-256 hash billions of times. It is de facto a leader election mechanism in an anonymous network. In Bitcoin source code, the mining and transaction validation are handled by different threads. Therefore, after decoupling the two processes, transactions can be verified without mining time. However, the major flaw of Bitcoin-Ng is that the leader node must always stay reliable, otherwise the network shall break apart. 

My design is to elect a validator committee that's dynamically every few minutes through competition of mining. After the committee is set, they vote for each transaction and propagate the transaction block to the entire network. If any validator fails it will be excluded from the committee. The block size and time will be dynamic so that they can scale up in future.

The other issue of Bitcoin is its hard coded 2100 million total supply cannot keep up with its growing demands. Therefore, Bitcoin shall always be subjected to price manipulation as more people are saving instead of spending. A cryptocurrency should have a stable price to function as a medium for exchange. I think the limit of supply should be removed. Instead, the supply of the currency should be adjusted according to the market conditions.

I've looked into the Tx index. It contains three columns, nFile, nBlockPos and nTxPos. The last two variables are integers indicating where the transaction can be found in a file. I don't understand how does Bitcoin retrieve one transaction. Does the Bitcoin client read the entire index into memory, then create a map that establishes the transaction and its position?

Thanks for the answer. The key I meant the transaction hash, since you need to supply a key to retrieve a value.

I see. So both wallet.dat and chainstate store unspent transaction data, but only those in wallet.dat are spendable right?

I saw that the serialized transaction is just a lump of data with a key, so how does Bitcoin find transactions associated with a single private key? Does it need to travserse all unspent tx to get the total balance?

So, the whole block is read into the memory when Bitcoin accesses it? How does Bitcoin lookup a transaction from a block file?

Hi, I can find few information on Bitcoin's storage. So I understand that blkindex.dat is for the block index and blk00x.dat for transactions. However I don't understand how is this index generated. I understand an index file speeds up data lookup. However LevelDB states it doesn't support index so how is this index used along with LevelDB data? Also, a transaction is a nested structure that contains multiple inputs and outputs. LevelDB is a key-value storage engine so how does it recognize the hierarchy of each transaction?

Hi, blockchain is much hyped right now. However we haven't seen many successful use cases beyond cryptocurrency. One issue is that as a decentralized system, Bitcoin's performance has suffered severely. What are some use cases that can only be realized with more scalable blockchain solutions?

How do you guanrantee PoS coins won't be controlled by a group of stakeholders? PeerCoin, NXT and BitShares all have tried yet their combined value is only a fraction of Bitcoin's, even not comparable to Etherem and Monero.

The PoW chooses a random leader per each block because the outcome of a mining hash isn't predictable. It's still much more difficult for any party to shutdown PoW than PoS. PoS is also more vulnerable to market manipulation.

Bitcoin isn't the first cryptocurrency, but nonetheless most successful. Before Bitcoin all other designs have failed. Why? Because Bitcoin was the first to use Proof-of-work as consensus and incentive mechanism in a peer-to-peer network. Proof-of-work serves as both leader election and protection against Sybil attack. Although it consumes huge amounts of energy, it is purposefully designed that way. No one has yet been able to take down Bitcoin yet. Some people have proposed Proof-of-stake and Byzantine Fault Tolerance based consensus, but they are all de facto centralized. If we consider the evolution of digital currencies to be continuous, then the consortium blockchain should have been born before Bitcoin do because its logical to extend a single server node to a group of trusted servers rather than random server nodes. However, no such digital currencies have lived to date. Proof-of-stake coins rely on stakeholders to be honest. But what if they were seized by the government, or their private keys hacked? Without open participation a blockchain will be no different than a centralized database, which creates a single-point-of-failure. Close blockchains are not necessarily worthless, but they do carry much higher risks than open blockchains. History has shown us no centralized agency has been able to withstand all challenges, even the US federal reserve hasn't. Beware of scams and only choose the worthy.

I'm not familiar with Mining pool. How each miner's share is decided?

You misunderstand my idea. The time for mining each block varies so that a miner cannot always hold the leader position. A pool-mining system is consisted of a fixed set of nodes, while my idea is to also award miners who found the hash in the second, third till nth place so that their work wouldn't be completely futile.

Because Proof-of-work is more like a lottery. The outcome of SHA256 is unpredictable. Therefore some miners might have spent more electricity while got no rewards. Also if someone has advantage of hashing power it could result in centralization

Why should the mining difficulty be increased? It's still require significant amount of computing power even to become the 100th winner

The current design of Bitcoin is to award only the first miner. This mechanism gives unfair advantage to the miners who possess more computing power. I came up with an idea to split mining reward among several miners. The top 100 miners all receive equal share for the reward and the combine of their hash will be used as the block hash. How practical is this design? What can be its vulnerabilities?

The similarity between Bitcoin and god: both are based on beliefs

山寨要看能不能突破比特币。比如Monero，加强隐私保密性，值得关注

Yes that's what I meant. The problem is that blockchain is very abstract idea so it's hard to explain it. What's the best way to reach you?

Hi there, I and my colleagues are working on a new blockchain design. It aims to provide high transaction throughput while retain decentrilzation in the meantime. We take decentralization as our priority because centralization creates single-point-of-failure. We want to make a video to demonstrate the big picture and the consensus mechanism of our new blockchain. However we are on budget so we are looking for true enthusiasts who have taste and passion of technology to help us We will compensate you after we successfully run our crowdfunding campaign.