Building a Blockchain in Under 15 Minutes - Programmer explains

Building a Blockchain in Under 15 Minutes - Programmer explains
I wanted to demonstrate that the concept of a blockchain that powers almost all of the modern cryptocurrencies is very simple at its core. 

Bitcoin, Ethereum, Litecoin etc all are based on this blockchain technology. Many people think that the blockchain is a complicated thing while at it's core its just a clever use case of hashes.

Enjoy guys!

CODE: https://github.com/ivan-liljeqvist/SimpleBlockchain


Hardware wallets:
♥ TREZOR https://trezor.io
♥ LEDGER NANO S https://www.ledgerwallet.com/r/4607

To buy cryptocurrencies:
♥ Coinbase https://www.coinbase.com/join/529bab0ab08ded7080000019



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  • 김찬호
    I am watching one more person who read Satoshi's whitepaper
  • ishaan kesari
    Please tell some project where a started of blockchain can contribute?
  • calvin yip
    I am very new to block chain. May I ask you can block chain be implemented in a e-commerce website for example, like Amazon, , alibaba ,Craigslist , eBay?
  • Ayush Katiyar
    Nice work but correction is required at the time of changes in transaction you run code again the object can be created at different location in memory so instead of changing and then running it must be shown by changing the transaction array and printing the hash code before modifications and after modifications.
  • Jovan Davidovic
    Great video.
  • Arjun Govind
    Good vid Ivan!!!
  • Krunoslav Vrabec
    You're great!
    I'm a tech guy my entire life and was never interested in programming.
    You just changed that!
    Thank you!
    Hii sir ji my watsup no. 9253311354
  • Willy Willy
    Great work ! Bien ahí papá que buena explanation ! Me suscribo to your channel thank you !
  • Ricardo Viera
    Does block chaining deal with a digital signature?
  • Sean Livingston
    As a developer, I need to add blockchain development to my tool chain. Need to learn this while the demand is increasing, but the supply is low.
  • kyle lee
    Very important question- what in the hell is this man saying?!?!?
  • George28
    Круто наваливаешь!
  • Bim Collin Barneso
    Thanks for this video Ivan. I really like it... I had subscribe for your channel :) hoping for new vids about blockchain...
  • Winston Gary
    if you are a newbie or a beginner in cryptocurrency and you are looking for a working strategy this is the man that helped me make good profit in a week using his mining software and he is really good with it….he goes by the name is Mr Garald . I recommend his software for everyone. You can reach out to him via ( geraldphilips39@gmail.com) drop him a mail if you want to start making very good profit just like me in just hours.
  • Muhannad Tahboush
    At the beginning i would like to thanks you for your video, secondly i have simple question about blockchain.
    its possible to pass data or encrypted ticket from A to B through blockchain.
    Thanks a lot
  • Kjell Thorp
    I need to smoke some hash after this.... :)
  • Tony Fallows
    has me stuff
  • Dot Rule
    Total outsider with no tech knowledge but I understood what you were saying.
    Thanks, Ivan. Great job explaining.
    Btw, is there a more elaborate video for total newbies like me to learn more on how to use the program and such ?
  • prudhvi j
    How to become a blockchain developer.
    .without programming knowledge...pls tell me how to start where to start...step by step plese
  • Alexsey Orlov
    nice video, but where digital signature and where consensus algorithms ?
  • Csaba Toth
    "This kind of hash is very hard to crack" - wrong. The example could very well use MD5 or even better: SHA256. Very easy to use with Java. You could claim that it's very hard to crack then. The regular Java class's hash function is not a cryptographic hash function in the sense that it'd be hard to crack.
  • Sohail ali farooqui
    Great video for understanding the concept and implementation of hashing. I am trying to build a decentralized blockchain application for tracking charitable donations made by people from their bank accounts, any leads or tool which can help me out regarding this anyone ? I am well versed in java, javascript, html, css, C#, mySQL. Any help or pointing in right direction will be much appreciated.
  • Dr Williams
    I think I get it.. it's a bit like CRC error correction.. where it sends the end and the beginning tags of the packet "block" to make sure the ther side has received the same data. It's a receipt! That it ??
  • Santosh Nandur
    Can we use block chain technology in voting ? explain how it can be done
  • DSAS
    ok, so does a new blockchain figure a fork in an existing blockchain? and does that mean it´s more secure or easier to secure?
  • musa nuhu
    well Ivan I have been impressed
  • Vishnu Agrawal
    Excellent Ivan. Good job
  • Mozzthecoolguy
    Ivan, super stuff you made! Thanks a million!
  • Osh Bazar
    Can we create blockchain without Money or Economics? I wish to create a private personal blockchain only to store data. Will it be easy like this? I don't want block + chain. I want a single block that stores any information. And if it is private blockchain Can I delete, add, update data?
  • AB Softech
    how to upload blockchain in an crypto exchange, We made in JAVA
  • p473r
    how is this guy calling himself a programmer? "A hash is a digital signature"? seriously? He's using Java hashCode() for blocks??
    i mean you can just google these concepts in 2 minutes and find that most of what he's saying is completely wrong
  • Goutham Sivakumar
    What are the software or platform needed for blockchain using java code?
  • sal joe
    Excellent presentation; this gave me a good idea of how blockchain is implemented.
  • Morgan Warren
    Thank you, it was very interesting and affordable!
  • Bitcoin Cash
    This Kid needs a slap, lying to and scaming youtube subscribers and to the crypto community!
  • 张梓径
    Very misleading
  • DanHughes
    great job
  • Yovo Manolov
    This video is a killer ! Thank you very much. Very well explained!
  • Sola Han
    What if you lie right after the block is formed?
  • bitsflip
    Blockchain concept is "Simple yet profound!"
  • jacob nehama
    seared for python not java
  • E. tX
    HI IVAN, how to token 100 poems with a blockchain or holochain, to guarantee "authenticity" over them, could you develop it? thanks
  • 이용기
    Thanks!! your video is awesome
  • Cody Gonzalez
    Thank you, brother, I put my finger up! You really met in 15 minutes and everything was clearly explained!
  • julio A murillo
    DM on Instagram @seansoftengineer for software development, coding, programming, and app building. Tested and trusted, bet me he is pro
  • Ernie QT
  • Danilo
    could make a sales web wallet with its own node to handle private public keys please
  • parmila kargar
    Plzz kindly upload the soft copy of this software u write code on it.
  • parmila kargar
    On which program u wrote this code may I know?