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disqus: hackmd
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# Note for A Survey of Blockchain Applied to Smart Cities

## Q : Why we apply blockchain on smart city?

Challenge → Solution of blockchain

1. Number of data explode → decentralized system
2. Data may be modify → unauthorized modify in blockchain is not allow.
3. Sharing data to citizen → data in blockchain is transparent
4. Need incentive to encourage citizen participate → Blokchain has incentive mechanism

The main point in smart citizen and smart healthcare is storage and access right control which is an important part of blockchain.

# Application

## Q : If data in the future smart city's data is too big? How could we do?

Data may not all store in the blockchain. It could only store the key tag in blockchain or store the access policies with smart contract in the blockchain.

## My ideal of class contribution

Using blockchain to record the contributions of class may be a good ideal for the one who always answer the question to the classmates. Moreover, it can record the course student have take, send the proof of the education.

## Q : Is that using blockchain to build smart transportation a good ideal?

Using blockchain to build sharing car system. It is benefit for many people to use the resource that is idle asset just like uber.

An problem extend from it : If the car has problem. How does people know? It may combine with IoT device that can detect the problem of car.

To share the transportation, using the blockchain can record the use of it and can analyze the life time of the share car is an other benefit, too.

But it may not be like the u-bike, since less car can be transfer by car ( unless there is some kind of car for signal person)

## Q : How could we trust the data producer upload to the blockchain? Maybe they fake the data.

I think that is the problem like fake news. We may need some algorithm to detect and ban the company forever. Meanwhile, the fact that fake the data will leave in blockchain forever.

May be use IoT is another way to face the problem. On the other hand, the is the problem that can cooperate with government. This may combine with the smart farm we learn now. With the IoT and blockchain, producer will have less chance to fake the data, meanwhile people can ensure the resource of the products.

Government should regulate IoT device, since there may be many unstructured device with heterogeneous (composed of different kinds ) data.

# Challenge

## Security and privacy (which I think is important)

## Q : How can we store the data transparent, but also with privacy? Such as transparent transaction can use to analyze the money people have.

Since all the transaction can be trace in blockchain, anonymity is important in smart city.

Simple way: using new address of each transaction

Complex way:

Confident transaction, blind signature, ring signature, composite signature, mixing service, zero knowledge.

## Q : Beside of using DPOS as consensus, how can we increase the transaction number?

- Reducing the transaction size : Segregate Witness (SegWit) [ 230 ] separate digital signature and move it to the end, so the one blockchain can contain more transaction.
- Off-chain transactions : created to handle the multi-signature transaction off chain instantaneously and record the final settlement transaction
- Sharding : with blockchain shard, node are separated into different shard. In this way, transaction are process in parallel.
- Reducing the blockchain interval time : Two steps to build blockchain. Leader election and transaction serialization. In order to minimize collisions in leader election, leader need to select at low rate. The coupling of leader election and transaction serialization will cause a huge delay.Therefore, transaction serialization and leader election must decoupling for the throughput. In [ 235 ] [236] [237] has be adopted.
- TDAG-based system : transaction will be added into a graph, forming a graph of transaction. When new transaction join the tangle, it choose two previous transaction. A transaction is confirmed when it is approved by many other transaction. Since transaction do not need to wait a long time to be include in block, the IOTA's throughput is better than general blockchain.

## Q : What can blockchain do when we need decentralize computing?

Blockcahin can secure the data in cloud federation system by applied access control. As we mention above, access control by smart contract or record the access policies on blockchain.

One way is to ensure the cloud service provider is credibility and record the credit value on blockchain.

Another way to ensure is to record the operation history on blockcahin.

## Q : How to incentive people to use blockchain after the blockchain give all the coin that it could give?

After sending all of this money, the people record will need to give fee. Just like giving the money to bank, but it is different with bank. Bank can be collapsed, but not blockchain.

## Comment on blockchain can also be important

I think that supply chain is a way that build the reputation of producer. First of all, customer can know which producer did this thing. Second, if blockchain encourage people to comment and send reputation on blockchain, producer can have the feedback and also earn reputation or even money.

## Union business with blockchain

Using the business sharing information can make non-chain store be stronger. In union, store may share the point together and customer will not worry the point is useless. Moreover, if this blockchain is more popular, it can be like credit card. Giving some reward, and customer will be more willing to use it.

How could the reward's money come from? I will try to apply the business model in steemit. Current dilution annually in this blockchain will be like the fee from customer and store.

But how could make sure that money from store will keep investing ?

I don't have answer now. One way is that store will keep sending point they earn from the blockchain, they will need store some money to make sure the point is enough. ( I think this way is not quit safe)

## Summary

My opinion of blockchain that is a trusted storage way. We can also store the smart contract inside it. Most of usage in this paper is to check the data's security and some architecture will let you decide the policy of data access, so the data can be use to benefit ourselves just like the way being mentioned in smart healthcare.

To build a trust system is also blockcahin's advantage, so the smart car can share the information with each other. How about none want to share their own information? Blockchain has the incentive mechanism to encourage people to share.

Moreover, transparent data in blockchain can also benefit the world. The transparent data in electricity market can use to minimize the distance of transport power or build a green bond with traceability.

Last, the traceability in blockchain can be applied on product which can ensure the product origin and the quality. Ownest can also be prove by the supply chain and monitor product throughout its life cycle.

### paper that want to know more:

[106] [111] [114] [176] [179 ] [164] [165] [ 211 ] [ 230 ]

# Unfamiliar Word

consortium blockchain:

The blockchain used to record the cross-organization business transaction.

**Turing-complete:**

also called computationally universal. Turing completeness is used as a way to express the power of such a data-manipulation rule set. Virtually all programming languages today are Turing complete

**Stack-based program:**

also called stack-oriented program. It is the one relies on the stack-machine to pass parameters. Most assembly language are stack based program.

**Stack machine:**

The main difference from other computers is that most of its instructions operate on a push-down stack of numbers rather than numbers held in processor registers. Because the operands used in the instructions are always in a known location, the top of the stack, the instructions themselves do not require memory addresses or register numbers to supply their operands. This leads to an instruction set architecture (ISA) style known as a zero address format.

**Nonce:**

a nonce is an arbitrary number that can be used just once in a cryptographic communication.

Keep doing hash to block header, if it is less than target. It is the nonce we looking for.

cyber attack: Attack from internet

**TDGA** : ?

**Software defined networkingv (SDN)** :

Separate the controller from the data plane. We can change the controller without changing the hardware.

(https://www.notion.so/481bd7bee0b341c4b664700949fe1b3e#6b9eea80628b4d02810f6a153786a43c)

**Network Function Virtualization (NFV)**:

Virtualize the entire classes of network nodes function into building block that may connect, or chain together.

**Tacilte Internet:**

Make human's all sensory upload to the internet and communicate with machine.

**Proof of concept:**

Prove a short concept that can be feasibility, show the concept in it.

**homomorphic encryption :**

Generating an encrypted result which, when decrypted, matches the result of the operations as if they had been performed on the plaintext.

**What's confidential transaction and ring confidential transaction?**

###### tags: `Blockchain` `smart city` `paper`