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

2. Where’s my money scenario \w friend
3. Where’s my money scenario \w friend
4. Where’s my money scenario \w friend
5. Where’s my money scenario \w friend
6. Where’s my money scenario \w friend
7. Where’s my money scenario \w friend
9. KTB & people shouting “Where’s my money”
14. A Ledger
15. TODO: Neighborhood picture
16. A Centralized Approach
18. TODO: Centralized Problems
20. TODO: Centralized Problems
33. public class Transaction { private String sender; private String recipient; private int amount; // constructor, getters, setters, toString... }
34. public class Block { private final List<Transaction> transactions; // constructor, getters, setters, toString... }
35. public class Blockchain { private List<Block> blocks; // constructor, getters, setters, toString... }
44. public class Blockchain { private List<Block> blocks; private List<Transaction> pendingTransactions; // constructor, getters, setters, toString... }
45. // … // TODO: Implement Peer Synchronization // …
46. Fake Transactions
47. TODO: Rebecca buying a bike from Peter
50. // … // TODO: Implement Signatures // …
51. Making the Ledger Immutable
56. public class Block { private final List<Transaction> transactions; private final String prevBlockHash; private final String blockHash; // constructor, getters, setters, toString... }
57. Achieving Consensus
66. public class Block { private final List<Transaction> transactions; private final long nonce; private final String prevBlockHash; private final String blockHash; // constructor, getters, setters, toString... }
67. public BlockCandidate getMiningJob() { String lastBlockHash = blocks.get(blocks.size() - 1) .getBlockHash(); return new BlockCandidate( pendingTransactions, lastBlockHash); }
68. public void submitBlock(Block newBlock) { if (isValidBlock(newBlock)) { blocks.add(newBlock); } else { throw new IllegalArgumentException("Invalid block"); } }
69. private boolean isValidBlock(Block block) { // … // intermediary calculations… // … return prevBlockHash.equals(lastBlock.getBlockHash()) && calculatedBlockHash.equals(blockHash) && Utils.startsWithZeroes(blockHash, difficulty); }
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… }
71. Longest Chain Consensus
74. 51% Attack
82. public class Blockchain { private List<Block> blocks; private List<Transaction> pendingTransactions; private int difficulty = 4; // constructors, getters, setters, toString… }
83. TODO: Mining Rewards
84. // … // TODO: Implement Mining Rewards // …
85. • Live Demo
86. • Link to app in github
87. Act 3: Blockchain’s Evolution
88. Data -> Code
89. Data -> Code
90. Data -> Code
91. Data -> Code
92. Data -> Code
93. Smart Contracts
94. In Sum…
102. Data -> Code
103. It all sounds great but…
104. Blockchain is still a baby
105. Blockchain the next big thing & people laughing
106. The Earth is round & people laughing
107. Now is the time for pioneers
108. Now is the time for pioneers