# Integrated Blockchain and Edge Computing Systems: A Survey, Some Research Issues and Challenges

## What situtation?

Blockchain as digital cryptocurrency has recently attracted great attention, featured by it advantages in privacy and scalability improvement. It allows the participant in network to record the system in a distributed share.

In recent years, cloud-base application trend to moving form function of clouds to the network edge. Edge computing provide scalability in a distributed system and having efficient control in a secure manner and performances.


## Why we need to integrate?

However, consider covering the topic on network, storage and computation, the implement ability of intergration increase due their characteristic.

### Edge computing

The security of edge computing is challenge. Distributed structure driven edge computing has a lot of benefit. Nonetheless, this advantage remains potential security problems due to its technologies (e.g., P2P system, etc.) global-crossing services and local scales.

Some attack (e.g., jamming attacks, sniffer attacks, etc.) might involve during message transmission. Besides, it is hard to managing heterogeneous edge networks, which make attacker control the network easier.

### Blockchain

Blockchain requires significant storage space since Bitcoin become popular in 2017. Though the internet is already robust, it still shows a scaling limit to these kinds of decentralized networks.

Moreover, the transactions rate of blockchain can only on average 7-20 payments per seconds. Compare with nowadays VISA credit card, it can process over 2000 payments per seconds.

### Benefit of integrating

Integrating blockchain into edge computing enhances the security and privacy. Blockchain make it possible to build a lot of node on edge computing devices, and protect the accuracy, consistency and transparent way.

On the devices, devices, as an edge server, have more storage to save off-chain data for some multimedia applications.

## Requirement

To implement the integrating, reversal requirement needs to mat.

* Authentication:
Between multiple edges, they have to achieve agreement by signing smart contracts to validate their identities.

* Adaptability:
The diversity of devices and devices operating system are increasing. Hence, integrated system of blockchain and edge computing should be equipped with complexities, and the flexibility to adapt to the changing environment
* Network security:
To prevent attack (e.g., DDoS, etc.), we need to maintain distributed edge servers and make more efficient monitoring.

* Verifiable computation:
When loaded to some untrusted clients, we need to ensure results are correct. Therefore, the scalability of blockchain should guarantee the results.
* Low latency:
The main latency of an application composes of transmission latency and computation latency. Hence, the integration of blockchain and edge computing need to determine kinds of computation to make latency as low as possible.

## General Framework

1. The study [19] implement blockchain cloud architecture with software-defined networking (SDN),

## words
* PoW
* PoS