acorrenson / miniblock

A mini blockchain in python

miniBlock

A mini blockchain in python

exemple

Here is a little exemple

# create a new BlockChain with difficulty 4
chain = Chain(4)

# add a new block containing the transactions :
# "3 from Bob to Claris"
# "2 from Claris to Jean"
chain.addBlock( Block("3 from Bob to Claris, 2 from Claris to Jean") )

# check validity
chain.isChainValid()
# true

# let's try to modify the chain
chain.blocks[0].transaction = "9 from Bob to Claris, 9 from Claris to Jean"
chain.blocks[0].mine(chain.diff)

# check validity again
chain.isChainValid()
# false

doc

Block(data)

Block class.

• parameters :
  • data : string <= transactions stored in the block
• fields
  • index: int index of the block
  • hash: string hash of the block
  • prevHash: string hash of the previous block
  • data: string transactions written in the block
  • nonce: int nonce (to mine)
  • timestamp: string date of creation
• methods
  • getHash: string
  • checkDiff: boolean
  • mine: string

Block.getHash()

Calculate the hahs according to : self.index, self.nonce, self.data, self.prevHash, self.timestamp

• parameters : none
• return : string => self.hash

Block.checkDiff(diff)

Check if the hash matches with the difficulty

• parameters:
  • diff : int <= number of 0 needed at the begining of the hash
• return : string => self.hash

Block.mine(diff)

Increment the nonce to have a valid hash (according to a specific difficulty)

• parameters:
  • diff : int <= number of 0 needed at the begining of the hash
• return : string => self.hash

Chain(diff)

Chain class (block container)

• parametres :
  • diff : int difficulty to mine a block
• fields :
  • diff : int difficulty to mine a block
  • blocks : array container for all blocks
  • number : int actual number of blocks
• methods :
  • createGenesis : none
  • addBlock: none
  • getPrevHash : none
  • isChainValid : boolean
  • printChain : none

Chain.createGenesis()

Init the chain with a genesis block

• parameters : none
• return : none

Chain.addBlock(block)

Add a new block to the chain. (it mines the block before)

• parameters :
  • block : Block
• return : none

Chain.getPrevHash()

Compute hash of the last block and return it.

• parameters : none
• return : string => hash of the last block

Chain.isChainValid()

Check if all blocks match the difficulty and if all blocks have a valid hash.

• parameters : none
• return : boolean

Chain.printChain()

Display all blocks of the chain in the console.

• parameters : none
• return : none

Cheater

Just to have fun, we can try to cheat the chain with the cheater module.

cheat(chain, index, blockData)

Replace data in a specific block and reset hashs to have a valid chain again.

• parameters :
  • chain : Chain <= chain to modify
  • index : int <= index of the targeted block
  • blockData : string <= fake data to change
• return : none

exemple

chain = Chain(4)

# add a new block containing the transactions :
# "3 from Bob to Claris"
# "2 from Claris to Jean"
chain.addBlock( Block("3 from Bob to Claris, 2 from Claris to Jean") )

# check validity
chain.isChainValid()
# TRUE

# let's try to modify the chain
cheat(chain, 0, "9 from Bob to Claris, 9 from Claris to Jean")

# check validity again
chain.isChainValid()
# TRUE <= success