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#!/usr/bin/env python3
# Copyright (c) 2014-2018 Daniel Kraft
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
# Basic code for working with auxpow. This is used for the regtests (e.g. from
# auxpow_testing.py), but also for contrib/auxpow/getwork-wrapper.py.
import binascii
import codecs
import hashlib
def constructAuxpow (block):
"""
Starts to construct a minimal auxpow, ready to be mined. Returns the fake
coinbase tx and the unmined parent block header as hex strings.
"""
block = codecs.encode (block, 'ascii')
# Start by building the merge-mining coinbase. The merkle tree
# consists only of the block hash as root.
coinbase = b"fabe" + binascii.hexlify (b"m" * 2)
coinbase += block
coinbase += b"01000000" + (b"00" * 4)
# Construct "vector" of transaction inputs.
vin = b"01"
vin += (b"00" * 32) + (b"ff" * 4)
vin += codecs.encode ("%02x" % (len (coinbase) // 2), "ascii") + coinbase
vin += (b"ff" * 4)
# Build up the full coinbase transaction. It consists only
# of the input and has no outputs.
tx = b"01000000" + vin + b"00" + (b"00" * 4)
txHash = doubleHashHex (tx)
# Construct the parent block header. It need not be valid, just good
# enough for auxpow purposes.
header = b"01000000"
header += b"00" * 32
header += reverseHex (txHash)
header += b"00" * 4
header += b"00" * 4
header += b"00" * 4
return (tx.decode ('ascii'), header.decode ('ascii'))
def finishAuxpow (tx, header):
"""
Constructs the finished auxpow hex string based on the mined header.
"""
blockhash = doubleHashHex (header)
# Build the MerkleTx part of the auxpow.
auxpow = codecs.encode (tx, 'ascii')
auxpow += blockhash
auxpow += b"00"
auxpow += b"00" * 4
# Extend to full auxpow.
auxpow += b"00"
auxpow += b"00" * 4
auxpow += header
return auxpow.decode ("ascii")
def doubleHashHex (data):
"""
Perform Bitcoin's Double-SHA256 hash on the given hex string.
"""
hasher = hashlib.sha256 ()
hasher.update (binascii.unhexlify (data))
data = hasher.digest ()
hasher = hashlib.sha256 ()
hasher.update (data)
return reverseHex (hasher.hexdigest ())
def reverseHex (data):
"""
Flip byte order in the given data (hex string).
"""
b = bytearray (binascii.unhexlify (data))
b.reverse ()
return binascii.hexlify (b)
def getworkByteswap (data):
"""
Run the byte-order swapping step necessary for working with getwork.
"""
data = bytearray (data)
assert len (data) % 4 == 0
for i in range (0, len (data), 4):
data[i], data[i + 3] = data[i + 3], data[i]
data[i + 1], data[i + 2] = data[i + 2], data[i + 1]
return data
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