Introduction
Bitcoin and cryptocurrencies made a lot of noise lately. I have been rather disappointed by the turn the cryptocurrencies t...
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Thanks for this "Blockchain made easy" article. Really interesting.
I don't quite get one part: from your example, only the hash of the data is stored in the blockchain; isn't the data supposed to be decrypted later? Where are the data messages ("transactions") stored then, if not in the block chain?
well hash defines a unique signature of a block, in real practice, the block also contains an index value, a data(record of transactions), a timestamp , and also the golden nonce value.The cryptographic hash dont account for decryption. Its like the address part of a data-structure, and the data is stored in the data part of the data-structure.
Actually the point of the blockchain is to secure the immutability of data, not to encrypt it.
I'm very interested about an answer to your question. How would you implement it in the current example?
I'm interested in an answer from the author before proposing mine.
Too bad we can't tag people
thank you for the post it really cleared many concepts i was struggling to understand.
here is the implementation in python
first file
blockchainLib.py
the second file
main.py
Been dabbling in cryptocurrency mining lately, and never really understood what was going on behind the scenes until reading this. Much thanks!
On a lark, I was inspired to draft a really simple implementation in PHP:
thanks for the article ;)
in ruby:
Awesome explanation, really helpful! I'm just wondering why a hash is only valid if it starts with 0000 characters. I'm also not clear on how to use this blockchain for, say creating my own cryptokittens or some other application. How are the hashes in a blockchain connected to actual data?
The 0000 characters are called the difficulty. I chose those characters. They do not mean anything in particular, I could have picked anything. In Bitcoin for example, there is a concept called mining, where you have to 'solve' this difficulty by finding a valid hash. If the answer is found too quickly, the difficulty will be augmented for the next blocks( say 5 zeroes instead of 4 ).
I'll make another article to explain the connexion between hashes and data, I am getting a few questions about this :)
Nice article! To help me learn this I pulled out the js-sha256 to rely on node's crypto module directly and made some async/functional updates of my own along the way. Could be an interesting comparison for anyone who wants to compare imperative vs. functional and brings up the issue seen in real cryptocurrencies where the first miner to get a valid proof of work causes others to start over now that their 'last hash' value has changed. Code is here:
github.com/alanguir/blockchain/blo...
The revolutionary part is the distributed ledger - i.e. decentralizing one block chain to many clients so that any transaction on any client can be verified against the history of transactions on other clients.
Thanks for the breakdown. It seems simple enough. What's the revolutionary part of blockchains then, the part that Satoshi figured out? Did Satoshi just put out a proof that this is a valid way to do things?
The revolutionary part of blockchain technology (or at least one of its revolutionary features) is that you never have to trust a single user of the network. You only have to trust the technology because if that works, it's impossible to cheat the system.
I don't really get it. You can explain a bit more please ?
I think it's about decentralization, in a p2p network everyone has a copy of the blockchain (in case) and if one changes its pair this will generate an incongruity with the other pairs scattered in the nodes (computer, device) of the network, and your fake couple it would be excluded, therefore, no one should worry if a node is honest because he himself would denounce and punish himself by excluding himself from the network.
Great article! I've been wanting an good intro into block chain and this was perfect. However, when I ran the index.js file,
blockchain.getAllBlocks()
returnedundefined
. I got it to work by updating that function toconst getAllBlocks = () => blocks
.You are right, I updated the code in the article. Thanks for the catch!
So a blockchain is an encrypted Linked List?
Mhmm, I guess you could call it like that.
the blockchain itself is not encrypted, everyone can read (search: blockchain explore), it would be better to say that the blockchain is a list of concatenated hashes.
That is absolutely brilliant, Damien. Nothing like seeing it with your own eyes in order to understand it. Many thanks :-)
To help out anyone who is not at all familiar with node (hello, anyone there? ;-) ) here's a very simple way to run this:
Hope it helps.
Thanks for this article, but i think the devil is in details. Blockchain itself is a simple pattern, but it has nothing to do with real world blockchain powered p2p networks. In real application you need to spend much more code and time with such things like establishing secure socket connection, managing resources and implementing an idea of your cryptosystem (what it is and why it should help people live their lives in happiness).
P.S. there is no need in self-executing function if you use a node's require/exports system.
Two things:
Aside from that, it is a good article and thank you for posting it :)
I have a doubt!! Bitcoin!!!!
If people from multiple mining pool trying to find nounce for certain block, then how are they going to agree to validate the same transaction in that block? if they didn't agree to mine with same transactions, then how is blockchain going to verify that they did valid mining(I meant not cheating). There is still a possibility that they can cheat right? If other mining pool people took diff set of transaction to mine for a block, then obviously they ll get diff hash and so they can't compare with them with actual hash. and If only one pool would get incentive (12.5BTC) then how after one mining a block, some other pool is going to waste its compute power in verifying the transaction. Even if it did so, how is it going to resist to change as change is already done in the blockchain.
Someone, please help me out...
this is pretty cool. thanks to Blockchain
Would anybody like to volunteer to write the same in Java?
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
public class BlockchainExample {
}
New to Java and I was referencing this for a Security course. I'm getting BlockchainExample cannot be resolved to a type.
Hi there, could you specify in which line you are getting this error?
And also, did you copy all the code? Not only part on black? There are lines at the top
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
public class BlockchainExample {
and also one
}
at the end.
I have checked it minute ago - code works.
Neat!!! Thanks for the the simplistic approach to explaining what one formerly considered complex. Cheers!
it is not complex, it is complicated, the blockchain is complex in nature because a block is linked to the previous one. I hope I have made the concept.
Great article in simplifying a complicated process re: blockchain
Very helpful article !
Not sure about it but I tried my own in Python3
I don't get one thing. How to retrieve information from this Blockchain (the data Strings?)
This post did what all whitepapers couldn't - Explain the concept!. Great article Damien, thank you so much!
Great article.
I just have one small remark, the header image you used illustrates a kind of cyclic graph, which has nothing to do with blockchains as far as I know. This can be misleading.
Thank you for the article! very helpful.
Here is a block application building hackathon coming on this weekend July 14, 15. Let me know if anyone else is joining: bit.ly/2L2olS9
very Interesting and best for beginners
Hey would you please recommend a good online course on blockchain
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Very much impressed with the article.
Does each block contain one transaction in case of bitcoin?
How the bitcoin is generated? Who will generate?
Please fix "Their must" => "There must", plus "OOOO" => "0000".
Brilliant article nevertheless :)
Thanks a lot
Did we get an answer to how we retrieve the original data? How to see the messages in each block? Other than that, really good article! Well done!