PyBitmessage-2021-04-27/src/helper_ackPayload.py

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"""This module is for generating ack payload."""
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import highlevelcrypto
import helper_random
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from binascii import hexlify
from struct import pack
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from addresses import encodeVarint
# This function generates payload objects for message acknowledgements
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# Several stealth levels are available depending on the privacy needs;
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# a higher level means better stealth, but also higher cost (size+POW)
# - level 0: a random 32-byte sequence with a message header appended
# - level 1: a getpubkey request for a (random) dummy key hash
# - level 2: a standard message, encrypted to a random pubkey
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def genAckPayload(streamNumber=1, stealthLevel=0):
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"""Generate and return payload obj."""
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if (stealthLevel == 2): # Generate privacy-enhanced payload
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# Generate a dummy privkey and derive the pubkey
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dummyPubKeyHex = highlevelcrypto.privToPub(
hexlify(helper_random.randomBytes(32)))
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# Generate a dummy message of random length
# (the smallest possible standard-formatted message is 234 bytes)
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dummyMessage = helper_random.randomBytes(
helper_random.randomrandrange(234, 801))
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# Encrypt the message using standard BM encryption (ECIES)
ackdata = highlevelcrypto.encrypt(dummyMessage, dummyPubKeyHex)
acktype = 2 # message
version = 1
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elif (stealthLevel == 1): # Basic privacy payload (random getpubkey)
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ackdata = helper_random.randomBytes(32)
acktype = 0 # getpubkey
version = 4
else: # Minimum viable payload (non stealth)
ackdata = helper_random.randomBytes(32)
acktype = 2 # message
version = 1
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ackobject = pack('>I', acktype) + encodeVarint(
version) + encodeVarint(streamNumber) + ackdata
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return ackobject