Learn Blockchain By Building It

This is the talk I gave at the Code Monsters 2018 conference (https://2018.codemonsters.pro/).

In it, I go through the process of implementing a Blockchain system from scratch by covering the fundamental concepts around it and discussing the problems it solves. I have also supplied a Java implementation of a simplified Blockchain system in order for the audience to better understand the concept and play with the system.

It can be found at https://github.com/preslavmihaylov/noobchain

Transcript

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2. Where’s my money scenario
   \w friend
   

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3. Where’s my money scenario
   \w friend
   

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4. Where’s my money scenario
   \w friend
   

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5. Where’s my money scenario
   \w friend
   

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6. Where’s my money scenario
   \w friend
   

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7. Where’s my money scenario
   \w friend
   

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9. KTB & people shouting
   “Where’s my money”
   

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14. A Ledger
    

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15. TODO: Neighborhood picture
    

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16. A Centralized
    Approach
    

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18. TODO:
    Centralized
    Problems
    

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20. TODO:
    Centralized
    Problems
    

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33. public class Transaction {
    private String sender;
    private String recipient;
    private int amount;
    // constructor, getters, setters, toString...
    }
    

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34. public class Block {
    private final List transactions;
    // constructor, getters, setters, toString...
    }
    

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35. public class Blockchain {
    private List blocks;
    // constructor, getters, setters, toString...
    }
    

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44. public class Blockchain {
    private List blocks;
    private List pendingTransactions;
    // constructor, getters, setters, toString...
    }
    

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45. // …
    // TODO: Implement Peer Synchronization
    // …
    

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46. Fake Transactions
    

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47. TODO: Rebecca buying a bike
    from Peter
    

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50. // …
    // TODO: Implement Signatures
    // …
    

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51. Making the Ledger
    Immutable
    

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56. public class Block {
    private final List transactions;
    private final String prevBlockHash;
    private final String blockHash;
    // constructor, getters, setters, toString...
    }
    

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57. Achieving
    Consensus
    

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66. public class Block {
    private final List transactions;
    private final long nonce;
    private final String prevBlockHash;
    private final String blockHash;
    // constructor, getters, setters, toString...
    }
    

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67. public BlockCandidate getMiningJob() {
    String lastBlockHash = blocks.get(blocks.size() - 1)
    .getBlockHash();
    return new BlockCandidate(
    pendingTransactions, lastBlockHash);
    }
    

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68. public void submitBlock(Block newBlock) {
    if (isValidBlock(newBlock)) {
    blocks.add(newBlock);
    } else {
    throw new IllegalArgumentException("Invalid block");
    }
    }
    

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69. private boolean isValidBlock(Block block) {
    // …
    // intermediary calculations…
    // …
    return prevBlockHash.equals(lastBlock.getBlockHash()) &&
    calculatedBlockHash.equals(blockHash) &&
    Utils.startsWithZeroes(blockHash, difficulty);
    }
    

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70. public void mine(Blockchain blockchain) {
    // intermediary calculations…
    while (!startsWithZeroes(blockHash, difficulty)) {
    nonce++;
    String blockData =
    prevBlockHash + transactions + nonce;
    blockHash = Utils.calculateSHA256(blockData);
    }
    // submit mined block…
    }
    

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71. Longest Chain
    Consensus
    

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74. 51% Attack
    

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82. public class Blockchain {
    private List blocks;
    private List pendingTransactions;
    private int difficulty = 4;
    // constructors, getters, setters, toString…
    }
    

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83. TODO: Mining Rewards
    

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84. // …
    // TODO: Implement Mining Rewards
    // …
    

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85. • Live Demo
    

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86. • Link to app in github
    

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87. Act 3:
    Blockchain’s Evolution
    

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88. Data -> Code
    

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89. Data -> Code
    

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90. Data -> Code
    

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91. Data -> Code
    

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92. Data -> Code
    

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93. Smart Contracts
    

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94. In Sum…
    

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102. Data -> Code
     

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103. It all sounds great but…
     

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104. Blockchain is still a baby
     

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105. Blockchain the next big thing
     & people laughing
     

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106. The Earth is round & people
     laughing
     

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107. Now is the time for pioneers
     

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108. Now is the time for pioneers
     

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