Arvind Narayanan (@random_walker)’s best Twitter threads.
In 2018 the blockchain/decentralization story fell apart. For example, a study of 43 use cases found a 0% success rate. https://t.co/FTEKKCPAy8
Let's talk about some mistaken assumptions about decentralization that led to the blockchain hype, and what we can learn from them.
(For context, I think the technology is sound, interesting and important from a CS perspective. That’s why I’ve been researching and teaching it since 2013. https://t.co/FIbyZnzfzn But I’ve also been speaking/writing about the pitfalls of decentralization for ~10 years.)
Have you ever wondered why the meaning of sorting in computing (ordering or ranking) is different from its everyday meaning (dividing into piles or categories)? The answer has to do with the history of sorting going back 130 years and turns out to be really interesting.
Here’s an IBM card sorter (probably a type 083 from the 1950s). It is sorting punch cards into 10 piles based on a particular digit (units digit, tens’ digit, etc.) The operator can specify which digit/column to sort on by turning a knob. https://t.co/XNir8V3ttD
Suppose each card has a 3 digit number, and we do 3 passes through the machine — first sorting the unit digit, then tens, then hundreds. After each pass we collect the cards from the piles in order. Voila — the cards are now numerically ordered! This is the radix sort algorithm. pic.twitter.com/ksNwiSaRsN