# Note of: Applications of Blockchains in the Internet of Things: A Comprehensive Survey

### Architecture of the paper
other way is actually TDAG or DAG, blockchain's next development

# Question after look through the paper
## This paper seem to emphasize the consesus algorithms. Why?
Since consesus is an important trade off between performance and scalability for IoT applization.
Sharding mechanisms in Ethereum and Tendermint can lead to leveraging the benefits of higher performance, and calability for IoT applications.

## What policy of privacy on permissonless blockchain is implemented?
Almost no privacy, or you can combine the private layer
other way use encrypt method to maintain privacy.

## What's the problem after implement blockchain on IoT?
latency, since we have to encrypt. Choosing consensus is important.
And we need to develop a light node lighter than "light node". Issuing transaction may be the only thing it need to do. Compare in below.
privacy, in permissionless blockchain it can't hide the transaction record. Even if it can will face the crime problem and encrypt will increase the lantency.

## What is the benefit of multi-layer blockchain?
May combine both private and public blockchain, we can therefore have the privacy in blockchain.
If COSMOS successfully build, we can have inter-blockchain communication.

---
# Detial read

## Challenges of centralized IoT
- Cyber attack
- Limted control of data
- No accountability and traceability of data
- Number of IoT **expontial** growth

## What solutions blockchain provide
- Remove singular point
- End-to-End coumicate **don't** need to go to centralized server
- Data on blockchain has accountability and tracability
- Offer smart contract and treat IoT interaction as transaction
- Monetized in truly democratic service

## Four type of IoT edge device constraint in a blockchain-based IoT
1. Gateway device as end-points to blockchain
2. Device as transaction-issuers to the blockchain
3. Interconnected edge devices as end-points to the blockchain
4. Cloud-blockchain hybird with the IoT edge


## IoT Privacy through Blockchain
[105] add Privacy Validation Chain to maintain auditable
[109] soft ware define cloud compputing with blockchain base accesss control
**[112]** hybird approach, use a private cloud for IoT storage and a overlay blockchain for record all data transfer and IoT interaction.
**[86]** combine private and public chain together

**[33]** smart contract use to control the access (Want to know what detial)
[117] prevent signal vechial to be tied to a singular blockchain address
[125]use a vast number of presudonymous to mask vehicle

## Trustless IoT architecture with blockchain
Rencently, two research paths there.
1. More disseminate and IoT data
2. relies on a peer-to-peer approach for validation of transaction among participating entities

[131] Not sure what it talking about. Need more detial.

[135]
[138]use fog layer device as blockchain as IoT node instead of constrained IoT end-device

**Ubirch GmbH:** (Got to know it)
is currently offering a solution similar to a notary services for the IoT devices and their data, in order to provide trustworthiness on the data, from IoT devices

## Security of IoT
Old problem: may be tampered, may be attack, data may be misuse
- provide access control:
**[153]** to realize how smart contract is used to contol access policies
**[155]** handle big data, use smart contract to inform owner when big data is requested

- Maintain data integrity through blockchain:
[159] expand the scalability of smart vehicles.

- Ensue confidentality through blockchain:
**[151]** use smart contract to control the IoT command using there blockchain address

- Improving IoT availability
**[161]** use multi-layer blockchain to handle the security issue with resource constrained IoT device.

If we connect the IoT device to the blockchain, user can control the device directly to the device as transaction

**SmartAxiom**,for example, proposes an edge-oriented software based on blockchain technology, for the dentification and authentication of devices, as well as data integrity and privacy.

## Identity management
- Traditional Identity management:
OAuth 2.0 use token to grant or revoke access to specific online application
- Blockchain-based ID management for IoT:
[151]blockchain PKI
[129] smart card developed on the JC3.04 standard platform
- blockchain for IoT ID management in Industry:
**[Chronicled](https://chronicled.com/)** is a company that is using the IoT and blockchain to provide digital identity to physical products, while Riddle and Code22 offers its own hardware and software stack to provide any physical object with a unique tamper-proof identity.
**[DocAi](https://www.doc.ai)**, a platform focused on collecting personal information at large scale,
in order to build predictive machine learning-based models
for health analytics, with strict access control policies.

## Data management with blockchain
Since many IoT devcies are time critical, processing IoT data is important while considering the constrained capabilities of IoT device.
### Traditional in IoT
[187] \[188] address the problem of bottleneck of centralized problem, but is not liveness as blockchain.
as you can see most of it is centralized.
### Data of IoT stored in blockchain
**Latency** and **scalability** remain an open challenge for data storage within blockchains

**Benefit:**
1. enforce data integrity
2. non-dependence on semantics for logging IoT data

[101] [102] focuse on privacy reliability and integrity
[191] Sapphire parallelizes smart contract execution over the computational power available to it through varying IoT devices.

## monetization of IoT device
**lack** of standardization and interoperability among different vendors
**The types of vendors** in the IoT business models can be classified into four categories namely software vendors, hardware vendors, end-to-end service providers and connectivity providers
### monetization in centalized IoT
- hardware vendors:
sell device and gateway
- software vendors:
offer services that run on the back-end of the system on the cloud platforms and gateways primarily involving management of data and devices along with processing and analysis of data
- end-to-end service providers:
offer all the components in the IoT architecture from the end-devices to the cloud platform
- connectivity providers:
offer modules for communication among the different tiers

### monteization in decentralized IoT
We can ensure the granularity and data flow in the blockchain, and also monetizate.
**[167] [214]** They demonstrate high throughput of their proposed solution using permissioned blockchains for secure code distribution and immutable data storage
**[117]** developed an architecture for data sharing in vehicular edge computing, where they use consortium blockchains and smart contracts to enforce access control for data transfer,

there are a few startups that are focusing their efforts on the monetization of data generated by IoT devices in particular, thus creating a domain not only interesting for research, but also for new business models

**Try know more about the business model about this:**
**Slock.it**
**Filament** enable device to interact and transact
**Dalie**

## Alternative approach towards decentalized IoT
Now in blockchain is a sequential blockchain, but using DAG will improve saclability.
### BlockDAG
Challenge:
high rate of orphan
more honest node will be discard outside the longest chain.[219]
may contain conflict transaction

added benefit:
weaker miner can publish blocks onto smaller fork are also rewarded.

The blockDAG mechanism in [218], Spectre [220] and Jute30 allow contradicting transactions, but use sorting to maintain organization.
There is also another blockDAG not allow conflicting transactions
### TDAG distrubite ledger
Not a blockchain
Use TDAG for ++linking transactions++ together instead of blocks.
In blockchains, simply adding new transactions and not bundling them in blocks is not scalable, since there would be a huge rate of orphan chains. **This problem can be potentially solved using TDAGs**

example of TDAG: IOTA

Hybrid approaches involving blockchains and TDAG ledgers the Virtualized Distributed Ledger Technology (vDLT) as proposed by Yu et al. [224]

## ISSUES AND FUTURE RESEARCH DIRECTIONS
Three main challenge :
1. privacy-preservation
2. scalability
3. utilizing blockchains in scenarios involving devices with constrained capabilities

With other part:

### privacy-preservation
[235]zero konwledge implemention
[236]ring signature

### scalability
sharding [67] techniques
More promising solutions involve either ++moving processing++ and ++storage load off-chain++ or ++limiting the scope of consensus over different parts++ of a blockchain network, or ++developing inter-blockchain communications++ [247] for connecting multiple blockchains.
[247]COMOS

verical scaling:
scaling as a distribute database
horizontal scaling:
semantic independent inter blockchain communication

### IoT edge constrain
Blockchain platforms like Hyperledger’s Burrow [28] and Sawtooth [57] create roles for nodes in blockchain networks, including ++limited roles well-suited for IoT edge devices++, where nodes can ++simply push transactions++ to the blockchain without needing to store a full copy

Future:
extand blockchain to the IoT edge.
The challenge in this research direction would be to **enable IoT devices** and **gateways to push transactions** to the blockchain using light clients, ++without creating centralized block validation pools++.

### Trad off in public-private blockchain
- private blockchain:
Using rounds of voting to provide Byzantine fault tolerance. But still centralized
- public blockchain:
aim to create security and permissionless enviroment.

So, it is a trad of **high speed** and **decantralization.**

### SDN for blockcahin basedd IoT edge
Virtualized IoT through blockcahin will be a secure direction which we execute will yield.

## Unfamiliar word
- Byzantine fault:
https://medium.com/mibinews/%E7%BE%85%E6%96%AF%E7%A6%8F%E5%B0%88%E6%AC%84-%E6%8B%9C%E5%8D%A0%E5%BA%AD%E5%B0%87%E8%BB%8D%E6%80%8E%E9%BA%BC%E6%89%93%E7%9A%84%E5%8B%9D%E4%BB%97-a51f6c39a760
https://www.samsonhoi.com/570/blockchain-pbft

- Impersonation attack:
Impersonation attacks are emails that attempt to impersonate a trusted individual or company in an attempt to gain access to corporate finances or data.

- Collusion attack:
Collusion attack can be defined as the execution of operations that have the ability to combine multiple copies of the media or other files together so as to produce a new copy.

- COSMOS:
A blockchain link all the blockchain together.
Cosmos aims to become an “internet of blockchains” which is going to solve these problems once and for all. Cosmos’ architecture consists of several independent blockchains called “Zones” attached to a central blockchain called “Hub”.

- [Provenance](https://www.provenance.org/):
Main object to solve the supply chain problem.
As explain in website:
We help brands and retailers build customer trust through transparency. Using blockchain technology Provenance empowers shoppers to choose your product

- Sybil attack:
Singal usser creat multiple account to attack the network.
Blockchain with consensus will make this attack quit hard to implement.

- k-anonymity:
k-anonymity is a property possessed by certain anonymized data.
The concept of k-anonymity was first introduced by Latanya Sweeney and Pierangela Samarati in a paper published in 1998[1] as an attempt to solve the problem: "Given person-specific field-structured data, produce a release of the data with scientific guarantees that the individuals who are the subjects of the data cannot be re-identified while the data remain practically useful."

- javacard secure elements:
java card:
Java Card refers to a software technology that allows Java-based applications (applets) to be run securely on smart cards and similar small memory footprint devices.

- 'Trustless' in blockchain:
Means we distribute all the trust among everyone rather than single individual or entity.

- IPFS:
The InterPlanetary File System (IPFS) is a protocol and peer-to-peer network for storing and sharing data in a distributed file system.
https://www.samsonhoi.com/689/blockchain-ipfs-intro

- PKI (Public Key Infrastructure)
A public key infrastructure (PKI) is a set of roles, policies, hardware, software and procedures needed to create, manage, distribute, use, store and revoke digital certificates and manage public-key encryption.

- tokenized approach
is the process of substituting a sensitive data element with a non-sensitive equivalent, referred to as a token, that has no extrinsic or exploitable meaning or value. The token is a reference (i.e. identifier) that maps back to the sensitive data through a tokenization system.

- DAO attack:
explain:https://ethfans.org/posts/114
And is a little complex, not read yet.

- LTE:
is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA technologies

- cellular Network
A cellular network or mobile network is a communication network where the last link is wireless.
###### tags: `Blockchain` `IoT` `paper` `note`