chris-belcher

no versioning means saving just a seed phrase isnt enough

motivated by shitcoining
 see how bip44 works, many different coins with one phrase

destroys efficency
 must rescan several times

chris-belcher

Design for improving JoinMarket's resistance to sybil attacks using fidelity bonds

13/7/2019

tl;dr

JoinMarket can be sybil attacked today at relatively low cost which can destroy its privacy. Bitcoins can be sacrificed with burner outputs and time-locked addresses (also called fidelity bonds), and this can be used to greatly improve JoinMarket's resistance to sybil attacks.

With real-world data and realistic assumptions we calculate that under such a fidelity bond system an adversary would need to lock up 30,000-80,000 bitcoins for months, or send 45-120 bitcoins to burner addresses to have a good chance of sybil attacking the system if it were added to JoinMarket.

chris-belcher

How Wasabi Wallet and Samourai-Wallet-Whirlpool slightly degrade the divisibility of bitcoin

December 2018

I made this claim on twitter recently and many people wanted me to go into more detail.

Lots of privacy tech in bitcoin like coinjoin, coinswap, tumblebit and Lightning Network require many entities to come together to agree to make certain kinds of transactions. This creates a requirement that the right resources (coins) have to be in the right place,

chris-belcher

#jsonrpc.py from https://github.com/JoinMarket-Org/joinmarket/blob/master/joinmarket/jsonrpc.py
#copyright # Copyright (C) 2013,2015 by Daniel Kraft <d@domob.eu> and phelix / blockchained.com

import base64
import httplib
import json

class JsonRpcError(Exception):
    def __init__(self, obj):
        self.code = obj["code"]

chris-belcher

r/btc markets itself as a "censorship-free" sub. In reality it attempts to silence the voices of people it disagrees with.

A few screenshot examples of censorship https://imgur.com/a/rHrtC

this article was deleted when posted, which describes how the mods of r/btc are roger ver's employees at bitcoin.com https://medium.com/@WhalePanda/the-curious-relation-between-bitcoin-com-anti-segwit-propaganda-26c877249976#.4mfo9qn3e

"Exploit code for the recent BTU attack - apparently this was posted to /r/btc, and of course, got censored. :)"

chris-belcher

JoinMarket with off-chain fees

17/01/2019

Problem: Single JoinMarket coinjoins aren't private enough

A single JoinMarket coinjoin often doesn't hide which inputs belong to the maker(s) and which belong to the taker. This is because the coinjoin fee is included on-chain.

To tell apart takers' inputs from makers' inputs, subset matching can be used. The taker's subset is

chris-belcher

Plan to improve the privacy of JoinMarket's tumbler script

24/02/2019

JoinMarket has a tumbler application which aims to send bitcoins in a way that delinks the origin and destination.

I have some thoughts on how and why to improve the tumbler algorithm.

Feel free to bikeshed some of these parameters (averages, counts, etc), as my important points are about other stuff.

chris-belcher

list of links for quick copypasting when debating on forums, also useful as a reading list

this was posted on reddit, link is https://www.reddit.com/r/Bitcoin/comments/7mh8c2/long_live_decentralized_bitcoin_a_reading_list/

some of these links may be subject to linkrot, try looking on archive.org or archive.is

Summary / The fundamental tradeoff

a trip to the moon requires a rocket with multiple stages by gmaxwell https://www.reddit.com/r/Bitcoin/comments/438hx0/a_trip_to_the_moon_requires_a_rocket_with/

chris-belcher

The Problem

JoinMarket has a problem where it assumes different nicknames have different bitcoin wallets. This can be exploited by people running multiple yield generator bots from the same wallet, so they get a higher rate of profit at the expense of de-legitimizing the system for privacy.

Crypto primitive 1: Merkle Tree

A merkle tree is a way of producing a commitment to a set, which can later can prove that elements are contained within the set using only O(logN) data, and only revealing one other element in the set.

For example here is a merkle tree commiting to a set of numbers {6, 3, 9, 0, 8, 4, 7, 2}

chris-belcher

https://www.reddit.com/r/Bitcoin/comments/cgryi1/international_energy_agencys_report_on_bitcoin/

78% of bitcoin mining uses renewables https://twitter.com/C_Bendiksen/status/1068221424777814016 apparently because of their cheaper marginal cost

debunking of the nature paper https://twitter.com/nic__carter/status/1056976815032582144

https://twitter.com/Beetcoin/status/935460412262375424

https://hackernoon.com/the-reports-of-bitcoin-environmental-damage-are-garbage-5a93d32c2d7 reddit thread: https://www.reddit.com/r/Bitcoin/comments/almsef/the_reports_of_bitcoin_environmental_damage_are/