A Note On Blockchains

Blockchains have three components, a data structure, a set of replicas, and a consensus mechanism:

• The data structure is often said to provide immutability or to be tamper-proof, but this is wrong. It is made out of bits, and bits can be changed or destroyed. What it actually provides is tamper-evidence, revealing that the data structure has changed.
• If an unauthorized change to the data structure is detected the damage must be repaired. So there must be multiple replicas of the data structure to allow an undamaged replica to be copied to the damaged replica.
• The role of the consensus mechanism is to authorize changes to the data structure, and prevent unauthorized changes. A change is authorized if the consensus of the replicas agrees to it.
  

Below the fold, some details.

Liability In The Software Supply Chain

Atlantic Council Report On Software Supply Chains was already rather long when I got to the last of the report's recommendations that I wanted to discuss, the one entitled Bring Lawyers, Guns and Money. It proposes imposing liability on actors in the software supply chain, and I wrote:

The fact that software vendors use licensing to disclaim liability for the functioning of their products is at the root of the lack of security in systems. These proposals are plausible but I believe they would either be ineffective or, more likely, actively harmful. There is so much to write about them that they deserve an entire post to themselves.

Below the fold is the post they deserve.

Moxie Marlinspike On Decentralization

The Ecosystem Is Moving: Challenges For Distributed And Decentralized Technology is a talk by Moxie Marlinspike that anyone interested in the movement to re-decentralize the Internet should watch and think about. Marlinspike concludes "I'm not entirely optimistic about the future of decentralized systems, but I'd also love to be proven wrong".

I spent nearly two decades building and operating in production the LOCKSS system, a small-ish system that was intended, but never quite managed, to be completely decentralized. I agree with Marlinspike's conclusion, and have been writing with this attitude at least 2014's Economies Of Scale In Peer-to-Peer Networks. It is always comforting to find someone coming to the same conclusion via a completely different route, as with scalability expert Todd Hoff in 2018 and now Moxie Marlinspike based on his experience building the Signal encrypted messaging system. Below the fold I contrast his reasons for skepticism with mine.

Don't Say We Didn't Warn You

Just over a quarter-century ago, Stanford Libraries' HighWire Press pioneered the switch of academic journal publishing from paper to digital when they put the Journal of Biological Chemistry on-line. Even in those early days of the Web, people understood that Web pages, and links to them, decayed over time. A year later, Brewster Kahle founded the Internet Archive to preserve them for posterity.

One difficulty was that although academic journals contained some of the Web content that  was most important to preserve for the future, the Internet Archive could not access them because they were paywalled. Two years later, Vicky Reich and I started the LOCKSS (Lots Of Copies Keep Stuff Safe) program to address this problem. In 2000's Permanent Web Publishing we wrote:

Librarians have a well-founded confidence in their ability to provide their readers with access to material published on paper, even if it is centuries old. Preservation is a by-product of the need to scatter copies around to provide access. Librarians have an equally well-founded skepticism about their ability to do the same for material published in electronic form. Preservation is totally at the whim of the publisher.

A subscription to a paper journal provides the library with an archival copy of the content. Subscribing to a Web journal rents access to the publisher's copy. The publisher may promise "perpetual access", but there is no business model to support the promise. Recent events have demonstrated that major journals may vanish from the Web at a few months notice.

This poses a problem for librarians, who subscribe to these journals in order to provide both current and future readers with access to the material. Current readers need the Web editions. Future readers need paper; there is no other way to be sure the material will survive.

Now, Jeffrey Brainard's Dozens of scientific journals have vanished from the internet, and no one preserved them and Diana Kwon's More than 100 scientific journals have disappeared from the Internet draw attention to this long-standing problem. Below the fold I discuss the paper behind the Science and Nature articles.

Amazon Is Profitable?

Six years ago, in Two Brief Updates I first wrote about Benedict Evans' insightful analysis of Amazon's financial reports:

He shows how Amazon's strategy is not to generate and distribute profits, but to re-invest their cash flow into staring and developing businesses. Starting each business absorbs cash, but as they develop they turn around and start generating cash that can be used to start the next one.

He is now back with a similarly insightful analysis entitled Amazon's profits, AWS and advertising, which starts:

People argue about Amazon a lot, and one of the most common and long-running arguments is about profits. The sales keep going up, and it takes a larger and larger share of US retail every year (7-8% in 2019), but it never seems to make any money. What’s going on?

Below the fold, some details of Evans' explanation.

Open Source Saturation

In Supporting Open Source Software I discussed the critical need for better support for contributors to open source projects. Now, Quo Vadis, Open Source? The Limits of Open Source Growth by Michael Dorner, Maximilian Capraro and Ann Barcomb presents statistical evidence suggesting that this problem is affecting the vitality of the open source environment. Follow me below the fold for the details.

Shout-Out To Gutenberg Project

I've mentioned before that my father spent his whole career, apart from WW2 as an RNVR watch officer on convoy escorts, at Harrods, the iconic London department store. He even published a textbook on retail distribution. So I can't resist a shout-out to the amazing work of Eric Hutton and the volunteers of Project Gutenberg who, over the last 13 years, have scanned, OCR-ed and proof-read the entire Harrods catalog from 1912. Below the fold, the details.