# 散列 Hash
https://zh.wikipedia.org/wiki/%E6%95%A3%E5%88%97%E5%87%BD%E6%95%B8
----
- 散列函数把消息或数据压缩成摘要，使得数据量变小
- 如果两个散列值是不相同的（根据同一函数），那么这两个散列值的原始输入也是不相同的
- 好的散列函数在输入域中很少出现散列冲突
- 冲突少意味着很难找到产生相同散列值的数据
----
F = X % 100
F(1) = F(101) = F(xx01) = 1
----
MD5
SHA-256
---
# 区块链 Blockchain
https://en.wikipedia.org/wiki/Blockchain
https://academy.horizen.global/technology/advanced/blockchain-as-a-data-structure/
----
----
----
---
# p2p 分布式 共识
---
## Hashcash
https://en.wikipedia.org/wiki/Hashcash
----
生成需要大量计算，验证需要很少计算
Hash(content + nounce) < 100000000
101010101010
000111010001
000011010101
---
## 工作量证明 POW
---
# 比特币
---
## 非对称加密
---
## 记账
---
## Who am I?
- Front-end developer
- VSCode :heart:
- I use tabs. :cat:
---
### 70% of our users are developers. Developers :heart: GitHub.
---
{%youtube E8Nj7RwXf0s %}
---
### Usage flow
---
```graphviz
digraph {
compound=true
rankdir=RL
graph [ fontname="Source Sans Pro", fontsize=20 ];
node [ fontname="Source Sans Pro", fontsize=18];
edge [ fontname="Source Sans Pro", fontsize=12 ];
subgraph core {
c [label="Hackmd-it \ncore"] [shape=box]
}
c -> sync [ltail=session lhead=session]
subgraph cluster1 {
concentrate=true
a [label="Text source\nGithub, Gitlab, ..."] [shape=box]
b [label="HackMD Editor"] [shape=box]
sync [label="sync" shape=plaintext ]
b -> sync [dir="both"]
sync -> a [dir="both"]
label="An edit session"
}
}
```
---
### Architecture of extension
---
---
## Content script
- Bind with each page
- Manipulate DOM
- Add event listeners
- Isolated JavaScript environment
- It doesn't break things
---
# :fork_and_knife:
---
<style>
code.blue {
color: #337AB7 !important;
}
code.orange {
color: #F7A004 !important;
}
</style>
- <code class="orange">onMessage('event')</code>: Register event listener
- <code class="blue">sendMessage('event')</code>: Trigger event
---
# :bulb:
---
- Dead simple API
- Only cares about application logic
---
```typescript
import * as Channeru from 'channeru'
// setup channel in different page environment, once
const channel = Channeru.create()
```
---
```typescript
// in background script
const fakeLogin = async () => true
channel.answer('isLogin', async () => {
return await fakeLogin()
})
```
<br>
```typescript
// in inject script
const isLogin = await channel.callBackground('isLogin')
console.log(isLogin) //-> true
```
---
# :100: :muscle: :tada:
---
### Wrap up
- Cross envornment commnication
- A small library to solve messaging pain
- TypeScript Rocks :tada:
---
### Thank you! :sheep:
You can find me on
- GitHub
- Twitter
- or email me
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