Blockchain.FromScratch.StepByStep

#This is code for the stream. You can watch it live here.

#Encoding f(x) = y, g(y) = x #Hash Function f(data) = code

Doesn't exist: g(code) = data

Collision: f(x1) = y, f(x2) = y, x1 != x2

Probably: f(x1) = y, f(x2) = y, x1 = x2

Guarantied: f(x1) = y, f(x2) = z, y != z, x1 != x2

#Encryption f(data, key) = cryptotext

Doesn't exist or too expensive:

g(cryptotext) = data

g(cryptotext, data) = key good encryption

#Asymmetric encryption f(data, publicKey) = cryptotext

g(cryptotext, privateKey) = data #Digital Sign f(data, privateKey) = cryptotext

g(cryptotext, publicKey) = data => is was encrpyted by private key ##Verify Identity Alice: Encrypt this, please - randomHash

Bob: f(randomHash, privateKey) = cryptotext

Alice: g(cryptotext, publicKey) = randomHash => It is definitely Bob

#Blockchain

• block(parentHash, data)

block(null, data1)
block(hash(data1), data2)
block(hash(hash(data1) + data2), data3)
block(hash(hash(hash(data1) + data2) + data3, data4)

##Transactions

• Address is public key
• Address owner holds privateKey

Transaction(
   From // Sender's publicKey
   To // Receiver's publicKey
   Ammount,
   Sign // Sign(From + To + Ammount, Senders privateKey)
 ) 

###Verify Transaction

1. From is the owner of asset at the current state of chain
2. Transaction is signed by From's privateKey