28 May 2016

Bitcoin Deanonymization

How's it going with that 'online bitcoin course', last mentioned in Going Deeper into Bitcoin (March 2016)? At that time I wrote,
It took me exactly a week to work through the first two lectures. I'm sure that I won't be able to maintain this pace week after week, and I only skimmed the readings.

I've reached lecture six where I found an interesting image in '6.2 Overview of Bitcoin Deanonymization'. At about 11:40 into the video, the following chart is shown.

A similar chart can be found in the paper A Fistful of Bitcoins: Characterizing Payments Among Men with No Names Sarah Meiklejohn et al. The caption there (p.9) says,

Figure 6: A visualization of the user network. The area of the cluster represents the external incoming value; i.e., the bitcoins received from other clusters but not itself, and for an edge to appear between two nodes there must have been at least 200 transactions between them. The nodes are colored by category: blue nodes are mining pools; orange are fixed-rate exchanges; green are wallets; red are vendors; purple are (bank) exchanges; brown are gambling; pink are investment schemes; and grey are uncategorized.

Also interesting -- to me, at least -- are the 16 bitcoin services listed in the chart:-

bitcoin.de, bitcoinica, bitmit, bitpay, bitstamp, btc-e, deepbit, gibse, instawallet, mtgox, mybitcoin, okpay, ozcoin, satoshi btc dice, silk road, slush

Since few of those are household names, I'll look at them in another post.

21 May 2016

The MIT Connection

Adsense is everywhere. A few days ago I was working on a different topic when Google served an ad for bitcoin. I followed it and received something about an MIT white paper. Going further required me to enter an email address and since the ad promised only an 'excerpt' of the document, I stopped there. Afterwards I started to wonder if I could locate the original document. Using the obvious search terms I discovered Enigma (enigma.media.mit.edu).
Enigma is a decentralized cloud platform with guaranteed privacy. Private data is stored, shared and analyzed without ever being fully revealed to any party. Secure multi-party computation, empowered by the blockchain, is the magical technology behind it. [...] Want to dive in the technical details? See our whitepaper!

Sounds interesting, but first I wanted to look into the MIT Media Lab, a group whose name pops up repeatedly in bitcoin discussions. More search terms led to The Media Lab Digital Currency Initiative.

The goal of the Media Lab Digital Currency initiative is to bring together global experts in areas ranging from cryptography, to economics, to privacy, to distributed systems, to take on this important new area of research.

Anything else of interest from MIT? There's the MIT Bitcoin Club (bitcoin.mit.edu; 'Come discover Bitcoin!').

We believe Bitcoin has the potential to be not just a digital currency, but the future of money. While it is still in the early stages, we see Bitcoin as a protocol or platform on which financial and non-financial transactions can be conducted and verified as part of a global public ledger. Bitcoin lies at the intersection of several important academic research areas, including cryptography, distributed computing, graph theory, finance, and economics. The MIT Bitcoin Club seeks to provide forums where Bitcoin-related ideas, projects, programs, events, and businesses can be studied, discussed, and developed. Through club activities, we seek to increase awareness and use of Bitcoin within and beyond the MIT community.

There are also several recent stories on MIT's $900k Bitcoin Developer Fund (28 March 2016; coindesk.com).

MIT announced today it has raised $900,000 to fund the work of three bitcoin developers. The Bitcoin Developer Fund, backed by venture capitalist Fred Wilson, LinkedIn co-founder Reid Hoffman and others is intended to give the three bitcoin coders working to resolve the block-size debate and other similar technical challenges an academic platform from which to work.

These days $900K doesn't buy much development time ('the money will cover salaries, travel and support of bitcoin protocol development efforts'), but with bitcoin evolving so quickly, short time frames are probably best.

14 May 2016

Lightning, Malleability, Getting Hammered

The previous post, Bitcoin in the News : 2016-04, included an obvious follow-up.
The most repeated stories involved a couple of products. The first product was something called 'lightning'. [...] Since neither story explained what 'lightning' is, I'll pursue that in a future post.

The obvious search parameters lead to the product's home page (the term 'service' would be more accurate): Lightning Network, 'Scalable, Instant Bitcoin/Blockchain Transactions', explained with a 55 minute video. The site's 'How it Works' page explains,

The Lightning Network is dependent upon the underlying technology of the blockchain. By using real Bitcoin/blockchain transactions and using its native smart-contract scripting language, it is possible to create a secure network of participants which are able to transact at high volume and high speed.

Let's go back a year, to Could the Bitcoin Lightning Network Solve Blockchain Scalability? (coindesk.com; March 2015):-

The blockchain's increasing size continues to raise concerns about its ability to accommodate transaction growth. But, could a decentralised system where transactions are sent over a network of off-blockchain micropayment channels solve the ledger's scalability problems? Joseph Poon and Thaddeus Dryja, the developers behind the Bitcoin Lightning Network, think so.

That article points to a (much-referenced) white paper, the lightning-network paper-DRAFT-0.5.pdf:-

Abstract: • The bitcoin protocol can encompass the global financial transaction volume in all electronic payment systems today, without a single custodial 3rd party holding funds or requiring participants to have any more than a computer on a home broadband connection. A decentralized system is proposed whereby transactions are sent over a network of micropayment channels (a.k.a. payment channels or transaction channels) whose transfer of value occurs off-blockchain. If Bitcoin transactions can be signed with a new sighash type which addresses malleability, these transfers may occur between untrusted parties along the transfer route by contracts which are enforceable via broadcast over the bitcoin blockchain in the event of uncooperative or hostile participants, through a series of decrementing timelocks.

Malleability?

simple.wikipedia.org: • Malleability is the ability of a metal to be hammered into thin sheets. Gold and silver are highly malleable. When a piece of hot iron is hammered it takes the shape of a sheet. The property is not seen in non-metals.

Bitcoin malleability? From bitcoin.org/en/glossary, Transaction Malleability, Mutability:-

The ability of someone to change (mutate) unconfirmed transactions without making them invalid, which changes the transaction’s txid, making child transactions invalid.

I think I get it. Imagine the blockchain getting hammered. It turns out this happened last year; The Who, What, Why and How of the Ongoing Transaction Malleability Attack (bitcoinmagazine.com; October 2015):-

For the past several days, the Bitcoin network has been plagued by a so-called “transaction malleability attack.” Bitcoin users have experienced a number of annoyances, causing confusion and frustration. And while the transaction malleability issue is well-known and has plagued the Bitcoin network before, to many it is still unclear what it is, why it is a problem, who is causing the attack right now, and what can be done about it.

That's good to know, but I'm getting off track. Malleability might be an issue, but there are more fundamental concerns. From Debunking the 11 Most Stubborn Lightning Network Myths (bitcoinmagazine.com; October 2015, a week after the previous link -- a coincidence?):-

Earlier this year, [Poon & Dryja] released the Lightning Network white paper. In it they theorize how a layer on top of the Bitcoin blockchain can allow for instant and cheap bitcoin transactions, while vastly improving its scalability. As a result of the block-size limit debate, the Lightning Network has been getting a lot of attention lately. But, unfortunately, wild myths have started to dominate the discourse. Suddenly thrown in the middle of a long-lasting conflict of visions, Poon and Dryja's concept is hailed both as the great savior solving all of Bitcoin's problems – and as a source of deep corruption within Bitcoin's development community. [...]
• Myth #1: Core developers are crippling Bitcoin to force users onto the Lightning Network.
• Myth #2: There is no conflict of interest for the Core developers employed by Blockstream.
[...]
• Myth #11: The Lightning Network is urgently needed.

That's enough for now. I might not know how Lightning works in detail, but I know enough to understand that it's controversial. I'll let the controversies play out and come back to the subject if its evolution merits a deeper look.

07 May 2016

Bitcoin in the News : 2016-04

What a difference a month can make. The main story in the previous month's news roundup, 'Bitcoin's nightmare scenario' (aka the 'hard fork' debate; see Bitcoin in the News : 2016-03) was hardly newsworthy in April. Were we just witnessing marketing hype? Instead of sky-is-falling hysteria, there was routine evolution.

The most repeated stories involved a couple of products. The first product was something called 'lightning'.

Since neither story explained what 'lightning' is, I'll pursue that in a future post. The second product was something called 'steam', which a preliminary story helps to explain.

I don't want to judge whether that is positive or negative for bitcoin, because gambling contains elements of both. What does gambling have to do with steam?

A couple of well known personalities from the U.S. financial scene also made the bitcoin news.

What would a 'Bitcoin in the News' post be without some scandal? Like tax evasion...

Or like bribery...

The word 'myth' also popped up a few times during the month.

  • The New Bitcoin Myth (theatlantic.com); URL: 'bitcoin-hype'; Headline: 'Can Bitcoin Be Used For Good?'; except for the page title, the word 'myth' doesn't appear in the article
  • 7 myths about the Bitcoin blockchain (cio.com.au); 'Myth 1: The blockchain is a magical database in the cloud. Myth 2: The integrity of the ledger is defined by the majority of nodes [...]'

As that last link suggests (and this present post confirms), web 'journalism' is based on lists.

Now I'll look into the crystal ball at 'Bitcoin in the News : 2016-05', because there's one bitcoin story that was, that is, and that ever will be.

I could go on (and on and on), but let's give it a rest. Sap rises in the spring and bitcoin is no exception.