Effortless custom blockchain

Merkle tree

buildTree :: Hashable a => [a] -> Tree a can be used to build a hash tree containing all the elements of the list as its arguments, e.g.,

> putStr $ drawTree $ buildTree "doge"
0xaef9224b -
  0x64009ddb -
    0x00000064 'd'
    0x0000006f 'o'
  0x6700a28a -
    0x00000067 'g'
    0x00000065 'e'

Proofs

Proof that an element belongs to a tree with a specific root is defined as the path (from the root to the leaf), each element of which contains information which descendant contains the element of interest and the hash of the second descendant.

> buildProof 'o' $ buildTree "sol"
Just (MerkleProof 'o' <0x6c00aa70>0x00000073)

Blockchain

Blockchain is simplified and based on "Proof of Work" scheme.

mineBlock :: Miner -> Hash -> [Transaction] -> Block
mineBlock miner parent txs

creates a block that is a valid extension of a chain terminated with parentHash and containing txs transactions.

Block consists of a header and a list of transactions:

data Block = Block { 
  blockHdr :: BlockHeader,
  blockTxs :: [Transaction]
}

data BlockHeader = BlockHeader {
  parent :: Hash, 
  coinbase :: Transaction, 
  txroot :: Hash -- root of the Merkle tree
  nonce :: Hash
}

where nonce is proof of work - value such that the header hash meets a given condition.

Tests

Inline tests beginning with >>> sequence are placed in modules and can be tested with doctest, e.g.,

$ doctest Doctests.hs
Examples: 26  Tried: 26  Errors: 0  Failures: 0