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How would you explain blockchain technology to a layman? How is it decentralized?

The explanation would have to be short and to the point. It shouldn't include too many confusing details.

I'd tell a layman that a blockchain is a distributed ledger, which means that there are multiple copies of the ledger on multiple computers on the internet. It's entries are organized into blocks of a certain length. Numbers called a hashes are calculated with the data contained by each of the blocks as the input. The calculation is done using a very complex formula that outputs a long number from which it is impossible to know the data from which it was calculated but which is always the same if the input is the same. Each block contains the hash of the previous block. This way, the blocks form an unbreakable chain in which you can't change anything afterwards without the numbers not adding up. 

Because copies of the ledger are maintained on many different computers, there has to be a consensus regarding which version or versions are correct. It is a vital question who gets to make a new block that has a number new entries in it. 

There are different kinds of consensus types, the oldest of which is one where every candidate for a block maker has to perform expensive calculations before they can participate in a lottery where the winner gets to make of the next block. That way, if the cheat and it is noticed by the others who get the same entries reported to them, they will have worked for nothing. That incentive keeps them honest. Another type of consensus mechanism is one where only those who have sufficient proof of ownership of the system get to participate in the lottery. Because they have a lot to lose by cheating they will be honest. 

In both types of consensus mechanisms, the other keepers of a copy of the ledger (called nodes) confirm the blocks after which they become a permanent part of the blockchain.

Blockchain technology is about achieving consensus for storing data even in the presence of adversarial participants. You can seriously stop here to appreciate blockchains, because the important properties are that it stores data in a way that cannot be tampered with by any single party. Whatever invariants are baked into the consensus algorithm can be trusted to hold by the network.

The original flavor of consensus, proof of work consensus, relies on a particular class of problems which are prohibitively expensive to solve (where the difficulty can be chosen to be arbitrarily hard) but trivial to verify.

The data to store is gathered into a "block" along with the solution to the chosen problem which is agreed upon by the protocol. This problem will involve the previously accepted block, so that these blocks form a chain. Each block in the chain contains data as well as the solution to a problem that refers to the previous block.

These are propagated to all participants, and the protocol dictates that the longest chain is the valid chain. Because the solutions are easy to verify, the network can agree on whether a given chain of blocks is valid. The difficulty is set so that the solution can be produced every set amount of time (10 minutes, say) which means adding onto the longest chain takes awhile to compute. This makes it difficult for multiple chains to develop because for two competing chains, one will fall behind eventually, and then get rejected by the protocol.

Note that with enough computational power, an adversary would be able to generate blocks faster than the rest of the network, allowing them to decide what a valid block is, and this is referred to as the 51% attack. But for a long running chain with many diverse participants and total computational power, this state is seen as infeasible to achieve for an attacker.

Other blockchain variants tweak the consensus algorithm that decides who can add the next block, but I'll leave that out of this answer.

The main take-away: Blockchains are about establishing a protocol for who can commit the next set of data, in a way that prevents a single party from corrupting the data. The chain of blocks in the name come directly from the proof of work consensus algorithm .
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That more or less depends on what you consider a layman i suppose.

To some with zero computer knowledge the easiest way to explain what a blockchain is is first to clarify that bitcoin is NOT blockchain

blockchain like that is actually nothing more than a ledger, as ledgers go, they have been used since written history to keep track of transactions ... the ancient south americans used ropes tied with knots , the egyptians had papyrus, the medievals here parchment, then paper, then computers, but the medium doesnt matter

a ledger is a ledger and a blockchain is just that, a big digital book of transactions , ideal for bookkeeping but to creative "hackers" ofcourse there's more options to it

the difference between your classic ledger (be it tied knots, papyrus, parchment, paper, floppies, dvds, flash drives or sd cards that hold them) is "the" blockchain

removes the need for third party verification , it is built in such a way that transactions can not be forged , so in order for two people to make any transaction they don't need a bank, or notary, or any third legal party to make sure neither of them is cheating because they simply can't

because of the way it's built, that's since the original blockchain as developed in shady chatrooms by satoshi nakamoto and his band of shady characters lol ... and thats been a while (i personally mined about one BTC on a gpu, go figure how long my beard is ... but i lost it when mt gox ripped everybody off too, but thats not the subject here)

BITCOIN was in fact the original application of blockchain but the people behind it were actually quite revolutionary in their ideas, they didnt think about the blockchain, they thought about a system that would take it out of the hands of big government. A lot of marketeers today talk the talk on independence and crypto-anarchy but most of them were playing with lego and playmobil back then. The original team of nakamoto is not very well known, and Satoshi nakamoto himself has actually simply disappeared, no claim for fame, no claim for money (after all, the first bitcoins mined have to be his :p so if they come out, well...)
those people are called cypherpunks, hackers with a fetish for encryption and privacy , they don't really like the spotlight , and they could care less about fame, its like they just said like "here, have a cookie" to the worl

and today people are acting all big on blockchain as if they invented sliced bread, but no one mentions the fact that there would be zero cryptonnaires, and zero startups , unless nakamoto had written that whitepaper and his shady cypherpunk gang had helped him develop it.

(thats the short version lol)

blockchain is a ledger to keep track of transaction without the need for verification by trusted third parties ...


if you have someone a bit tech-savvy you could explain it like this, after you explain the first section here on what it actually is (practically) you could explain that

a blockchain is a sequential file

note : all files are in fact sequential files, databases just make use of pointer to jump to sections but at machine level , no matter the snazzy name it gets no matter the sql or oracle involved , its all a sequential stream of ones and zeroes, each and every one, even multitasking is an illusion ... even with multiple cpus the data has to come together and even with multiple threads there's switching as they execute but i'm switching timelines here again , the problem of having a bridge that can actually get info simulataneously is not the issue here )

a blockchain is a sequential file, the name is actually an excellent metafor

it is a series of "blocks" linked together by "hashes" (a hash is more or less what your password woud be once it gets decoded, but thats a whole wiki page so you could google that)
mining is somewhere comparable to brute force hash cracking lol, in the beginning cpus , then gpus then specialized hardware, not farms of specialized hardware

( https://qz.com/1056236/take-a-walk-around-one-of-the-worlds-biggest-bitcoin-mines/ )

usually placed in places where electricity is affordable lol ... these machines go through sequences of numbers until they find the right hash,

what is "the right hash" ?

a block in a "block"-chain can only have one single position between two others

they are linked by hashes in a way that theres only one place possible, if one hash gets changed, the whole subsequent chain would

"fall apart" is not the right word but it wouldnt work because everything around it wouldnt fit anymore

that's why it's a block - chain

a chained ledger of blocks that can't be altered , because if you change one, all the others have to change, thats why you need plenty of "nodes"

as you have witnesses on steemit , to make sure no single person has the power to simply alter the whole

i hope this clarified it a little bit

if you want to go all out you could read this :


otherwise, just remember a blockchain is a ledger, coins are applications of that (on that) as are the dapps you get here , musing, steemit etc, the underlying "technology" is blockchain

et bon, ca tape dur mais c pas si difficile a envisager

a chain with shackles where every shackle only fits exactly between exact two others and never between any or two different ones ...?

whew ... half an essay again, i think i need some iced-tea

When I am conducting a lot of Steemit seminars to students, explaining the technology that powers behind the Steemit platform is my goal first before jumping on to explaining what Steemit is all about.

When I explain blockchain technology, as much as possible I want to use terms that are common to peoples mind. So when I explain blockchain technology,

"A blockchain technology is like a record book that keeps all of the transactions happened on the network then updates all of the users regarding what is recorded. So it becomes transparent to all. Everything that has happened is recorded in the blockchain then updates all of the users about this happening"

Other terms for blockchain : ---> public database, record book, public ledger

If you wish to know more about people's thoughts on how they explained blockchain, you can see this post form sndbox asking the people "How would you describe blockchain in 1 sentence" and be amazed by how they described blockchain : 


The biggest spice of this post was there are words that are not allowed to use like :

 Extra points if you can articulate it without the using the following words...


While all of these answers are great-they don't exactly answer the first question.
How to explain Blockchain in layman terms.
I got this from John Hall:
He will talk about Bitcoin but Blockchain can be thought as the same thing.
However at the end I will explain why Blockchain does not equal Bitcoin. Not everything needs a blockchain.
Imagine a giant wall of letter boxes, each with a glass door. A crowd of people stand watching the letter boxes. Inside some of the boxes are coins. The crowd can see how many coins are in each box.

The crowd watches as a person steps forward with a key, opens a box, takes a coin, and deposits into the slot of another box. A clerk in the corner of the room writes this transaction into a ledger book. “Coin moved from box 4 to box 10.”

Time passes and more people step forward with keys, open individual boxes, and move coins to another. All the while the clerk in the corner is busy keeping track.

When approximately 10 minutes pass, the clerk closes his book and invites anyone in the room to solve a puzzle. A few people with huge calculators step forward. The first to solve the puzzle gets the honour to place the completed book on the shelf of official records. Good job buddy! The clerk rewards the winner with some newly minted coins.

This 10 minute cycle of record keeping continues so long as there are people in the room watching the boxes.

*The glass boxes are wallet addresses. Visible to all.
*The key is your wallet password. Keep it safe.
*The crowd is anyone running the bitcoin client software.
*The smart guys with big calculators are the miners.
*With a big enough calculator, anyone can try to mine.
*A book for every 10 minutes is a “block”.
*The shelf of books is the “blockchain”. All transactions ever, safely stored for anyone to read.

Why is a crowd of people watching a bunch of glass boxes important?

Before Bitcoin, a security guard would watch the boxes. Think of your bank, VISA or PayPal.

What if the guard caught a virus and got ill? What if the guard took a nap during some downtime? These mistakes happen when there is a single point of failure, like bank account details on a database.

Before Bitcoin, the keys were held on the guards belt. We trust the guard, of course, but must answer a number of personal security questions to gain access to our key.

Are we comfortable with the guard knowing so much? What if the guard lost the key? What if someone figured out the secret answer to our key? What if the guard sold our personal information? Not all guards are good.

With Bitcoin the whole world is watching the boxes all of the time. No one can lie, cheat or spend a coin in two recipient boxes at once. You hold the key to your box.

Remember always, with Bitcoin there’s no guard. If someone pickpockets your key, there is no one to turn to for help.

Bitcoin uses POW aka using a powerful computer to secure the network. POW is nothing new but Nakamoto using Adam Back Hashcash created an POW that can be used as a currency.
Miners mine blocks.
Say there are 10 miner groups.
One miner group however has 51% of all the miners. With this huge number they overpower the chain. You might think-how does Bitcoin prevent this? By paying them. If miner does attack, Bitcoin will switch to a diff POW system.

There is POS an alt to POW where you replace miners with shareholders. The user/pool who has 51% of all coins securing the system control the blockchain. This is bad due to if you want to get rid of these bad actors you have to block their coins which ain't decentralized.... POS blocks this in theory bc you are risking your money aka "shares" and if 51% you lose the value...

Why Blockchain ain't useful for everything. You see in Bitcoin there is a 3-7tps limit. You could inc by inc the blocksize but that makes it harder for the recorder of the network aka nodes to store the info. Bitcoin Cash claims that only Miners full nodes matter.... but let me ask you this?
How is it decentralized if only like 10 people store information?
EOS and EOS scale by doing DPOS. Where people vote based on stake for Miners+Nodes which are called witnesses. They get paid to secure and if get bad in theory get kicked out.. A better system than Bitcoin cash but this still leaves the blockchain only stored in about 150 places. Steem is perfect with DPOS bc Social network needs to be free use and DPOS only provides safe zero fee txs.

Bitcoin is still the most decentralized coin in the world. With the most nodes(that 8500 number is only the public listing nodes, by default Bitcoin Core clients hide full nodes. The hiding nodes do the same thing as listening nodes except are private lol). So Bitcoin being true to it aspects of letting everyone store info plans on scaling by the LN.
This video will explain it to you:

As such Blockchain can be thought as decentralized secure but more expensive and slower form of databases.
A blockchain is a list of transactions that are grouped together into blocks, with each block being validated.

For the earliest blockchain, Bitcoin, transactions are transfers from one account to another. For later blockchains different types of transactions were created. For example Steem transactions include upvotes and posts as well as transfers.

For a decentralised blockchain there is no central entity responsible for validation of blocks. Each node on the blockchain network has a copy of the the list of transactions and when new transfers are made, new blocks of transactions are filled and then validated by the nodes.

Validation is necessary to ensure there is consensus between all nodes in the network as to the correct list of transactions and to prevent single nodes from creating fake transactions.

The process of validation varies depending on the type of blockchain.

Proof of Work (PoW) blockchains such as Bitcoin use a computing power competition for each block validation together with a rule that the longest chain takes precedence. A node would need more than 50% of the overall network computing power to make the longest chain themselves and validate fake transactions.

Proof of Stake (PoS) blockchains choose a random node for each validation, with the chance of being chosen dependent on the amount of Stake (i.e. the amount of the blockchain currency) held by the node. Nodes with more Stake will validate more blocks.
The blockchain is like the government, but with no people. There's no one to keep the balance, no one has power over others. It's the ultimate communism, but with everyone being physically unable to do something wrong, or get more power than others.
Depends who your layman is:

if it' your dad or uncle: tell them the banks will be replace as the choice of escrow as we no longer need to trust them with our money, and they don't even need to pay high interest, pay fees, or even trust anyone else anymore, especially the bankster, that's the power blockchain or DLT (Digital Encrypted Ledger Technology) technology gives or returns back to them

if it's your teen relatives: tell them the no longer need to share the value of their social media time with facebroke or snapchat, the they deserve to get paid for every thing they do online, and that's what blockchain or DLT technology does, increase their pocket money considerably

....the point here is, explain the benefit, almost nobody wants to know exactly why it works....but if they do, tell them it's old technology, there is a list (like your shopping list), double ledger (like balancing your checkbook or an accounting entries), and blockchain is merely a method of using triple ledge with 3rd giving security (if they want to know....just say 3rd is using encryption that currently can't be broken to safeguard security of the information so nobody can mess with it)
Blockchain technology is here to change the world as if we look after before some years there where many students who are not getting jobs and they were talented people who was not getting proper value for their work but after blockchain technology many big companies who were not even knowing about blockchain technology where now a days involve in this technology.

There were many blockchain events organised to know the importance of blockchain and many employee are working behind this technology and they are getting good amount of money.

Blockchain technology has improved many things as it has reduced the handwork which people where doing before in past and it has improved a lot of activities and we search in internet there are many sites which in reality pays for our browsing. Before blockchain era no one was paying a single penny in our pocket for spending our valuable time with their sites. The best example for this if google.

Google is the biggest search engine and even it is not paying a single rupee to any people who are using their browser but instead of using google if we user the decentralized platform name presearch we have great chance to browse and earn money as well.

The best thing in blockchain technology and decentralized platform are they have change the lifestyle and many people are earning good income source using this technology.

Tell them exactly what it is,,

The Blockchain is a chain of records that cannot be altered. Once something is written to the chain it is set as set in stone and cannot be undone.

It is a permanent record that can be looked back on at any time by anyone.

Different Blockchains can be used for storing different records,

It is that simple. After that it is what the blockchain is used for. Depending on the blockchain you are talking about, you would alter what you say here.

Short sweet and simple. It also invites them to ask questions if they have genuine interest.

How do you explain blockchain technology to a layman? How is it decentralized?

Studying blockchain at first will cause a bit of confusion. Just like the beginning I studied blockchain is quite confusing. Here I will give a little reference for my friends to start studying blockchain one of the technologies behind the fast development of Cryptocurrency in the world. Here I will try to discuss this blockchain as easy as possible, because blockchain is actually a simple and simple technology.

Basically in the field of technology activities carried out is data processing, and in the processing of data that many elements - elements in it such as where the data is placed, how data is made, how the data is distributed and others.

As we know at this point any data that we are centralized or only stored in a single computer we call the server. The current system has many disadvantages, one of which is data security is not maximal because the data is only located in one place where it makes our data can not validate the data. The other is a problem if there is a system failure of the server will make the network down if we do not have a backup then it loses the data we have.
so for beginners or a layman about blockchain follow me