A block chain is a data structure that stores time-ordered data in an ever-growing list, like an accounting ledger (分类账簿). The block chain data structure is maintained using a distributed, peer-to-peer network of computers with no central “master”. As with many new concepts, block chain technology generates much optimism and also a huge amount of interest and excitement. Just what is it good for?

In short, block chains may improve any process where people need to access, confirm, send or store information securely. This information could be a person’s identity, a product’s shipment history or digital property like money.

Typical databases, spreadsheets (电子数据表), and ledgers store information about objects, people, and the interactions between them. Much of the world’s information, from credit card transactions to medical and financial records, is stored in these types of systems.

These types of systems have considerable, well-documented weaknesses that arise from their being centralized. A centralized record is hard to understand and is exposed to unauthorized access or distribution. It is also, because it is a ‘master’ copy, exposed to permanent changing or deletion.

Block chains are also used to store information. Crucially, however, they differ in two ways.

First, information is parceled up into blocks and sealed. Bitcoin, for example, which is the most famous practical example of a production block chain, stores all transactions across the network every ten minutes or so in a single, newly formed block. Each block is then added to the previous one to form a chain.

Second, this “chain of blocks” is not stored centrally. Instead, each block is copied and distributed around an entire network of peers - be they individuals, public institutions, or businesses - using distributed ledger technology. (The terms “block chain” and “distributed ledger” are often used interchangeably; for the sake of clarity, block chain technologies tend to employ distributed ledger technology.)

Each time someone adds a new block to the chain, meanwhile it is added to everyone’s copy.

You often can choose a private setting when you browse(浏览) the internet. But be forewarned: It may not afford nearly as much privacy as you expect. That’s the finding of a new study.

Major web browsers, such as Google’s Chrome and Apple’s Safari, often a private-browsing option. It’s sometimes referred to as “incognito.” This option lets you surf the Internet browser and saves a record into its history of each page that you visited. And what sites you visit won’t affect the suggestions your browser makes the next time you’re filling out an online form.

Many people believe----incorrectly--- that the incognito setting protects them more broadly. Most believe it even after reading a web browser’s explanation of the incognito mode.

For instance, a new study had 460 people read web browsers’ descriptions of private browsing. Each person read one of 13 descriptions. Then the participants answered questions about how private they thought their browsing would be while using this tool. The volunteers didn’t understand the incognito mode.This was true no matter which browser explanation they had read. The researchers reported their findings on April 26 at the 2018 World Wide Web Conference in Lyon, France.

More than half of the volunteers thought that if they logged into a Google account through a private window, Google wouldn’t keep a record of their search history. Not true. And about one in every four participants thought private browsing hid their device’s IP address. That’s wrong, too.

Blase Ur was one of the study’s authors. He’s an expert in computer security and privacy in Illinois at the University of Chicago. Companies could clear up this confusion by giving better explanations of the incognito mode, his team says. For example, the browsers should avoid vague（模糊).The web browser Opera, for instance, promises users that “your secrets are safe.” Nope Firefox encourages users to “browse like no one’s watching.” In fact, someone might be. (If you’d like to know more about the research information, please click here .)

What may well be the oldest metal coins in the world have been identified at an ancient abandoned city known as Guanzhuang in China. Like many Bronze Age (青铜时代) coins from the region, they were cast in the shape of spades with finely carved handles. These ancient coins existed during an in-between period between barter (以物易物) and money, when coins were a novel concept, but everybody knew that agricultural tools were valuable.

Reading about this incredible discovery, I kept thinking about the way modern people represent computer networks by describing machines as having “addresses”, like a house. We also talk about one computer using a “port” to send information to another computer, as if the data were a floating boat with destination. It’s as if we are in the Bronze Age of information technology, grasping desperately for real-world reference to transform our civilization.

Now consider what happened to spade coins. Over centuries, metalworkers made these coins into more abstract shapes. Some became almost human figures. Others’ handles were reduced to small half-circles. As spade coins grew more abstract, people carved them with number values and the locations where they were made. They became more like modern coins, flat and covered in writing. Looking at one of these later pieces, you would have no idea that they were once intended to look like a spade.

This makes me wonder if we will develop an entirely new set of symbols that allow us to interact with our digital information more smoothly.

Taking spade coins as our guide, we can guess that far-future computer networks will no longer contain any recognizable references to houses. But they still might bring some of the ideas we associate with home to our mind. In fact, computer networks — if they still exist at all — are likely to be almost the indispensable part of our houses and cities, their sensors inset with walls and roads. Our network addresses might actually be the same as our street addresses. If climate change leads to floods, our mobile devices might look more like boats than phones, assisting us to land.

My point is that the metaphors of the information age aren’t random. Mobile devices do offer us comfort after a long day at work. In some sense, our desire to settle on the shores of data lakes could change the way we understand home, as well as how we build computers. So as we cast our minds forward, we have to think about what new abstractions will go along with our information technology. Perhaps the one thing we count on is that humans will still appreciate the comforts of home.