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Blockchain explained, for the average American
Michael J. House
July 12, 2019, 11:14 a.m.

A paper-printable Bitcoin wallet.  From Wikipedia Commons.

As Facebook prepares to market its own cryptocurrency, there may be some confusion about exactly what blockchain is and how it works.  This feature story attempts to answer those questions. ~ Editor

July 12, 2019 -- In 2008, a person (or a group of people) anonymously posted a technical paper online with a solution to a problem. He called himself Satoshi Nakamoto, and the solution that he wrote about became what we know today as the blockchain (and Bitcoin). The problem that he wanted to solve was called “double-spending.” Unlike physical objects, computer files and information can be copied perfectly and easily by anyone with a computer. If the file is supposed to be used as some sort of digital money this a big problem. Anyone can copy the information that’s supposed to represent the money and spend it in two places at once.

This had been an issue with the idea of digital money (not just a record of physical money, but an all-digital equivalent) since the idea had become widespread. The only solution until 2008 was to rely on a central organization to keep track of when money is spent and refuse to approve sales that use duplicated money. The issue, basically, was that there was no way for anyone to be able to trust that people who said they had money, really did have money.

Like most cool inventions, the blockchain is simple but can be applied to very complex problems. At its heart, it uses a hashing function. Hashing is when a lot of data is put through a mathematical meat grinder to make a shorter, unique key. For each set of data (files or pictures or text), there is only one correct hash. If you have the hash, there is no way to get the file back out. It’s like an identification number for digital things. For example, this is the hash of all the text in this article up to here:


And this is the hash with a “B” in front of “In 2008”:


It’s completely different- which is one of the most useful things about a hash: there’s no way to figure out what the text was from just the hash. But it is unique. If you copy all the text from “In 2008…” to “up to here:” and put it through the right hashing function (I used one called SHA-1 from this website), it should give you the same hash.

Nakamoto realized that if you take a bunch of data that you want to store, and you put it all together (into a “block”) and hash it, you can take that hash and put it in another block of data. Then you can do the same thing to a series of blocks, with the hash of each one going into the next block in the chain. On its own, a blockchain doesn’t stop anyone from changing some of the data and then re-hashing the entire chain, but it does mean that if you want to change data in the middle, then you must change every block from there to the end.

He made a rule to make this process more difficult: if a hash doesn’t have four zeros at the front, it’s not a “good” hash. If anyone sees a hash that doesn’t have four zeros at the front, then they know the data has been changed- the same way they know that the data has been changed if the next block in the chain doesn’t have the hash of the previous block in it. To stop people from tampering with a blockchain that a lot of people are working on, you don’t need to stop them- you just need to know if they have.

This rule means that anyone who wants to make a block to put on the chain must hash the data repeatedly, and each time they must change a number in the block so that the hash will be different. This is what mining is. When people are “mining” Bitcoin, they are changing a counter and hashing, then changing it again and hashing again and again until they get a hash that has the right number of zeros on one end. Computers can do this thousands of times a second until the hash is good.

Would-be forgers can still change data in the middle of the chain and then re-hash every block that comes after the forgery, but it’s harder. There are thousands of trustworthy people trying to create valid blocks of data to add to the chain, and (hopefully) a much smaller number trying to alter the chain. As long as there is more computing power devoted to building the chain than there is to changing it, then the forgers can never catch up to the front of the chain. If they can’t catch up, then there will always be a place in the chain where the hashes don’t line up, and we can tell that they’re trying to lie to us.

All of this might seem like an enormous waste of time, but it is one way to solve a hard problem that a lot of people were interested in: how do you share information between a lot of individuals and know that it hasn’t been tampered with- and more importantly, how do you do it without a central authority? This has implications not just for digital money, but for almost every kind of software that needs a network to work. People all over the world have designed thousands of different variations on this basic pattern, trying to find ways to store healthcare records, votes, and even legal contracts that store and release money on their own. It’s a wild, often dangerous gold rush to find the next generation of decentralized software.

Last Week's Feature
State accepting applications for falconers to trap birds
July 8, 2019, 1:15 p.m.

Falconers may apply for drawing granting permission to trap falcons.  Photo courtesy of TWRA.

July 8, 2019 – The 2019 application period for the trapping of a peregrine falcon to be used in falconry began July 1, according to the Tennessee Wildlife Resources Agency (TWRA).

The TWRA will award the permits to the winners of a draw to be held on Wednesday, Aug. 28.

The number of permits to be allowed for the taking of peregrine falcons to be used in falconry has increased from one to five, as announced in 2018 by the U.S. Fish and Wildlife Service.

Falconers may go to the Falconry Information and Application under the Law Enforcement section of the TWRA’s website to locate the print-ready application and also view the requirements. Resident and non-resident master and general falconers are eligible for participation in the draw.

Completed applications must be postmarked by Thursday, Aug. 15.

Another change made last year is the permits will be allowed statewide. Previously, Peregrine falcons were only allowed to be taken from counties located in the TWRA’s Region I (West Tennessee). One permit had been issued for the past seven years in Tennessee. The U.S. Fish and Wildlife Service awarded Tennessee its first permit allowing the trapping of one Peregrine falcon for the use in falconry in 2011.

The population of Peregrine falcons, through state and federal conservation efforts, has recovered enough since their near extinction in the early 20th century to allow for a limited take of these birds for the use in falconry.

For more information, contact the TWRA’s Walter Cook at walter.cook@tn.gov or (615) 781-6647.