The blockchain module

class blockchain.BlockChain(blocks=None, txindex=None, reward=10, difficulty=3)

A Block chain is:

• blocks: a list of blocks
• txindex: a dict of transactions (key = hash)
• reward: number of coins allocated per verified block
• difficulty: the current difficulty

add(bl, ignoredifficulty=False)

add block bl to the blockchain and perform some basic checks:

• does the difficulty match the current difficulty? (if ignoredifficulty, this is not checked for, use this only when loading blocks from a file)
• is nonce OK?
• is hash of previous block correct?
• is coinbase transaction well formed and does it create the right amount?
• does check_tx work for every transaction?

returns success,msg (if success is True then the block was added)

any_spent_txin(tx)

True if any of the inputs of a tx has been spent

check_tx(tx, stx)

Performs different checks to transaction tx and its signature stx

• is the signature of a transaction ok?
• is there any double spending in the transactions?
• is there enough funds for the transactions?

Returns True, message if success

False,message if the transaction has a problem

check_tx_funds(tx)

check if transaction input and output funds match

check_txin(tx)

check that: * all inputs reference same public key * the public keys in all inputs match the

public keys in the output in the previous transaction

count_funds(pubkey)

return all coins that have not been spent by pubkey

find_tx(h)

find a transaction by hash h

find_tx_block(h)

find the block where transaction with hash h appears

funds(txin)

find funds in txin

is_spent(txin)

True if txin is already spent in any previous transactions

spent_txout(tx)

a list of same size of the list of ouputs which has the hash of the transaction if spent otherwise empty string

tx_reindex()

Rebuilds transaction index from list of blocks

wallet(pubkey)

return all coins that have not been spent by a public key, as a dictionary with keys transaction hash, output number and value being the amount of coins

where_spent(txin)

return transaction where txin shows as spent

blockchain.alltxins(txlist)

returns a dictionary of all coins.TxIn in the list txlist of coins.Transaction. The dictionary key is the tuple (pubkey.N,pubkey.e,hash_prev,output_num) and the value is the number of times a particular txin appears as input in txlist.

blockchain.tx_check_sig(tx, sig)

True if transaction has been signed correctly

blockchain.tx_sig(tx, privkey)

Sign a transaction

Note: all the input transactions are assumed to be from the same public key, so we just sign using one private key which is assumed to be that of the only owner of all inputs In bitcoin transactions, there is a “script” describing which keys to use to verify that the transaction is legit