dyokomizo

$ ghci
GHCi, version 7.10.3: http://www.haskell.org/ghc/  :? for help
Prelude> let z = \s z -> z
Prelude> let s = \n s z -> s $ n s z
Prelude> let unchurch n = n (+1) 0
Prelude> unchurch z
0
Prelude> let n1 = s z
Prelude> let n2 = s $ s z
Prelude> let n3 = s $ s $ s z

AdamISZ

Fidelity Bonds in an Anonymity set

If timelocked outputs are used as fidelity bonds, there is some inevitable degradation in the anonymity of users of a system that requires such bonds. Part of this would be entirely unavoidable - in that when the utxo is spent, the CLTV nature of the scriptPubKey must be revealed, and in most scenarios this would probably watermark that the utxo was being used for a fidelity bond purpose. But what might be avoided is the tracing, or linking, of a particular utxo used repeatedly for the same purpose.

Concrete case: Joinmarket maker

To make the issue clearer, consider the specific case of Joinmarket, and the recent proposal on fidelity bonds by Chris Belcher [1]. Here, the fidelity bond would be used to sign an ephemeral identity used on a message channel. The user, having committed funds to the bond, would perforce re-use that same bond every time he reconnects to the trading pit and so what is currently a completely ephemeral identity (it can be changed as often as

chris-belcher

Financial mathematics of JoinMarket fidelity bonds

13/7/2019

4/4/2021 (edited fixing formula and adding two graphs)

7/5/2021 (added appendix 1)

To read the context see the main document Design for improving joinmarket's resistance to sybil attacks using fidelity bonds.

dysinger

# MOVED HERE https://gist.github.com/dysinger/2a768db5b6e3b729ec898d7d4208add3

AdamISZ

#!/usr/bin/env python
from __future__ import print_function
"""
Find/count JM transactions in blocks.
Ensure your joinmarket-clientserver virtualenv (jmvenv) is activated,
make sure your Bitcoin Core node is available and joinmarket.cfg is appropriately set.

Pass start and end block number:
`python jmtxfinder.py 400000 400200`.

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

jonasnick

# bitcoin-cli wrapper for running c-lightning with a pruned Bitcoin node
# (EXPERIMENTAL). It forwards all requests to bitcoind. If a getblock request fails,
# blockstream.info is queried instead. If your prune setting is high enough (2 weeks
# = 2016?) using this wrapper SHOULDN'T have security implications because the
# important blocks are still queried through your own bitcoind.
# Tested with c-lightning 0.6.2. Set the --bitcoin-cli=PATH option in c-lightning to
# the path of this file to use it.
BCLI=bitcoin-cli

getblock() {

AdamISZ

Described here is a variant of what has previously been published under the name "P2EP" or Pay-to-endpoint, in which A pays B but B contributes utxos, i.e. it's a coinjoin-payment.

I'm using the term "payjoin" here to refer to using that idea, but not including a URI/endpoint specific to B, and not allowing (as a merchant would) arbitrary payments, which opens up certain problems around snooping attackers (more on this below). So payjoin just means "A pays B but B actively participates and passes across utxos as extra inputs".

I'll defer a more features-focused and non-tech friendly description of what this means to a later blogpost.

ummjackson

# Requirement: pip install tweepy
import tweepy

# Credentials go here (generate at: https://apps.twitter.com)
auth = tweepy.OAuthHandler('consumer_key', 'consumer_secret')
auth.set_access_token('access_token', 'access_token_secret')

# Connect to Twitter
api = tweepy.API(auth)

achow101

Using Bitcoin Core with Hardware Wallets

This approach is fairly manual, requires the command line, and requires a patched version of Bitcoin Core.

Note: For this guide, code lines prefixed with $ means that the command is typed in the terminal. Lines without $ are output of the commands.

Disclaimer

I am not liable for any coins that may be lost through this method. The software mentioned may have bugs. Use at your own risk.