arowser

Fast Multiparty Threshold ECDSA with Fast Trustless Setup

Steven Goldfeder

Digital signatures authorize transactions in cryptocurrencies

Alice's device, containing her private key, is a single point of failure

Multiparty authentication

Instead of having a single device store your key material...
- You can split it into multiple devices

Designed your address as protected by multiple keys

Locate the section for your github remote in the .git/config file. It looks like this:

[remote "origin"]
	fetch = +refs/heads/*:refs/remotes/origin/*
	url = [email protected]:joyent/node.git

Now add the line fetch = +refs/pull/*/head:refs/remotes/origin/pr/* to this section. Obviously, change the github url to match your project's URL. It ends up looking like this:

Schnorr signature test vectors

Test vector overview

Hash function H(m) = SHA256(SHA256(m))
Hash function H(m) = SHA256(m)

Basics

For a private key x, the public key is xG.
A signature on the message m with private key x is (R, s) where R=kG, s=k+H(R,X,m)x.

Chainstate only download - Proof of Concept

Introduction

The bitcoin blockchain is currently (9th Sept 2016) 88Gig but the Chainstate is only 1.7 Gig. That is a factor of 50 different. One concern for bitcoin at the moment is a lack of full nodes. This is partly due to the length of time to download and process the blockchain from scratch. And in addition a significant cost of hosting a full node is the cost of bandwidth for serving historical blocks - and a lot of this is to nodes that start downloading the blockchain and then abandon. A node can still operate as a full node with just a valid chainstate - there is little need for the full blockchain. From my tests only 30% of chains that start syncing get to completion.

Overview of proposal

Every 100'th block nodes take a snapshot of the LevelDB chainstate database.
They then calculate a hash of hashes of that 1.7gig database (takes about 2mins).

What is this all about?

This tutorial will turn your Raspberry PI into a simple Bluetooth audio receiver, which plays music through connected speakers. It's like a regular car audio system, but it can be used anywhere and it's a good value.

   Audio source (i.e. smartphone) 
                |
                v
 (((  Wireless Bluetooth Channel  )))
 |

	### Keybase proof

	I hereby claim:

	* I am arowser on github.
	* I am arowser (https://keybase.io/arowser) on keybase.
	* I have a public key ASD17uAsEOGA_lpATznm8Il3ff0Ii8v-j2ravJIw6eC4Mgo

	To claim this, I am signing this object:

	#!/usr/bin/env python
	"""
	This script implements a handshake with a remote Lightning
	Network node; see BOLT8:
	https://github.com/lightningnetwork/lightning-rfc/blob/master/08-transport.md
	, which is the Noise-based transport protocol
	for Lightning network nodes.

	Specify server, port and remote node pubkey as three command line arguments;
	here's an example invocation:

	'use strict';

	// first, run sudo apt-get install jq nodejs npm
	// second, run npm install bluebird co to install dependencies, and make sure bitcoin-cli can run these commands.
	// third, run node thisScript.js and it will change all the addresses on your bitcoind into segwit addresses.
	var Promise = require('bluebird');
	var co = require('co');
	var exec = Promise.promisify(require('child_process').exec);

	var main = function() {

	#! /bin/bash
	set -e
	trap 'previous_command=$this_command; this_command=$BASH_COMMAND' DEBUG
	trap 'echo FAILED COMMAND: $previous_command' EXIT

	#-------------------------------------------------------------------------------------------
	# This script will download packages for, configure, build and install a GCC cross-compiler.
	# Customize the variables (INSTALL_PATH, TARGET, etc.) to your liking before running.
	# If you get an error and need to resume the script from some point in the middle,
	# just delete/comment the preceding lines before running it again.

	CREATE OR REPLACE FUNCTION public.json_append(data json, insert_data json)
	RETURNS json
	IMMUTABLE
	LANGUAGE sql
	AS $$
	SELECT ('{'\|\|string_agg(to_json(key)\|\|':'\|\|value, ',')\|\|'}')::json
	FROM (
	SELECT * FROM json_each(data)
	UNION ALL
	SELECT * FROM json_each(insert_data)