Repository of Presentation: https://github.com/ArturSkowronski/naivechain-java Presented: Bielsko-Biała Java User Group (Bielsko-Biała JUG), Kraków, 22.02.2018 (https://www.meetup.com/pl-PL/Bielsko-Biala-JUG/events/247764157/) Biorąc pod uwagę szalone skoki (i spadki) wszelkich kryptowalut, Blockchain jest na językach wszystkich developerów. Jednocześnie ilość mitów, klechd i legend jakimi obrósł osiągnęła już rozmiary które warto nieco uporządkować. W ramach tej prezentacji postaram się rozwiać niektóre z nich, a dodatkowo pokazać Blockchain od strony stricte programistycznej - w ramach sesji Live Codingu zaimplementujemy uproszczony, ale kompletny wariant Blockchaina, zbliżony do tego znanego z Bitcoina. Wszystko to używając naszej ulubionej Javy. Dodatkowo, postaram się wskazać jej wady i zalety i wytłumaczyć, dlaczego jak grzyby po deszczu zewsząd wyrastają alternatywne implementacje mające być lekiem na całe zło (i dlaczego zwykle nie są). Mam nadzieje uczynić całość interaktywną - jeżeli ktoś ma jakieś pytania będę się starał na nie odpowiedzieć podczas prezentacji. Moim celem jest żeby każdy wyszedł z lepszą świadomością tego czym Blockchain jest, a co nawet najważniejsze - czym z pewnością Blockchain nie jest. ___ Artur to developer z serduchem rozdartym między JVM (całościowo) i nowoczesnym JavaScript - przy czym. z bardziej dojrzałymi planami matrymonialnymi związanymi z tą pierwszą platformą. Nie może się powstrzymać przed testowaniem nowych technologii, nawet jeśli czasem wybuchają mu w twarz w wyniku nadużycia w projektach szpachli i taśmy klejącej. Obecnie członek zespołu VirtusLab realizujący projekty dla Tesco Technology. Część Dynamicznego Duetu którego lepszą połową jest pluszowa foka (ᵔᴥᵔ).

1. DEVELOPER’S PERSPECTIVE
BLOCKCHAIN

2. TEXT
HOW TO BECOME RICH
INVESTOR’S PERSPECTIVE

3. BITCOINAIRE
BLOCKCHAIN, ANYBODY ?

4. BITCOINAIRE

5. MtGox Fraud
Initial Whitepaper
Original Peak
WTF?

6. Initial Whitepaper
WTF

8. TEXT
George Soros
LIBERTARIANS
KILL THE BANKS AND BANKERS

9. TEXT
INVESTORS
UNCORRELATED ASSET

10. DEVELOPERS
BLOCKCHAIN TECHNOLOGY

11. TEXT

12. TEXT

13. TEXT

14. BLOCKCHAIN

17. DOUBLE SPENDING

18. TEXT
DUPLICATION OF INFORMATION

19. ?

20. TEXT
SCARICY OF MONEY

21. TEXT
LEDGER

22. CENTRALISED

23. TEXT
TRUST

24. TEXT
TRUST-AS-A-SERVICE?

25. TEXT
DISTRIBUTED LEDGER ?

26. POLITICALLY DECENTRALISED
ARCHITECTURALLY DECENTRALISED LOGICALLY DECENTRALISED

27. TEXT
CONSENSUS TECHNIQUE…

28. TEXT
…USING MATH

29. TEXT
LET’S CODEBASED ON NAIVECHAIN BY @LHARTIKK
@ARTURSKOWRONSKI/NAIVECHAIN-JAVA

30. TEXT
P2P (WebSockets) P2P (WebSockets)
P2P (WebSockets)

31. public class Block {
protected int index;
protected String hash;
protected String previousHash;
protected long timestamp;
protected Object data;
protected int nonce;
}
BLOCK PART

32. BLOCK PART
public class Block {
protected int index;
protected String hash;
protected String previousHash;
protected long timestamp;
protected Object data;
protected int nonce;
}

33. BLOCK PART
public class Block {
protected int index;
protected String hash;
protected String previousHash;
protected long timestamp;
protected Object data;
protected int nonce;
}

34. BLOCK PART
public class Block {
protected int index;
protected String hash;
protected String previousHash;
protected long timestamp;
protected Object data;
protected int nonce;
}

35. BLOCK PART
public class Block {
protected int index;
protected String hash;
protected String previousHash;
protected long timestamp;
protected Object data;
protected int nonce;
}

36. CHAIN PART
public class Blockchain extends LinkedList<Block> {
public Blockchain(Block block) {
this.add(GENESIS_BLOCK);
}
}

37. CHAIN PART
public class Blockchain extends LinkedList<Block> {
public Blockchain(Block block) {
this.add(GENESIS_BLOCK);
}
}

38. CHAIN PART
public class Blockchain extends LinkedList<Block> {
public Blockchain(Block block) {
this.add(GENESIS_BLOCK);
}
}

39. CHAIN PART
public class Blockchain extends LinkedList<Block> {
public Blockchain(Block block) {
this.add(GENESIS_BLOCK);
}
}

40. GENESIS BLOCK
public static final Block GENESIS_BLOCK = new Block(
0, //index
“e6337db8a921823784c14378abed4f7d7", //hash
null, //previousHash
1465154705, //timestamp
"Pozdro Bielsko-Biala!”, //data
0 //nonce
);

41. MINING BLOCK
public class BlockchainService {
Blockchain chain = new Blockchain();
public Block mineBlock(Object data) => {
Block newBlock = nextBlock(chain.getLast(), data);
chain.addBlock(newBlock);
return chain.getLast();
};
}

42. MINING BLOCK
public class BlockchainService {
Blockchain chain = new Blockchain();
public Block mineBlock(Object data) => {
Block newBlock = nextBlock(chain.getLast(), data);
chain.addBlock(newBlock);
return chain.getLast();
};
}

43. MINING BLOCK
public class BlockchainService {
Blockchain chain = new Blockchain();
public Block mineBlock(Object data) => {
Block newBlock = nextBlock(chain.getLast(), data);
chain.addBlock(newBlock);
return chain.getLast();
};
}

44. MINING BLOCK
public static Block nextBlock(Block prevBlock, Object data) {
int nextIndex = previousBlock.index + 1;
String prevHash = prevBlock.getHash();
long nextTime = new Date().getTime();
String nextHash = calculateHash(nextIndex, prevHash, nextTime, data);
return new Block(nextIndex, prevHash, nextHash, nextTime, data);
}

45. MINING BLOCK
public static Block nextBlock(Block prevBlock, Object data) {
int nextIndex = previousBlock.index + 1;
String prevHash = prevBlock.getHash();
long nextTime = new Date().getTime();
String nextHash = calculateHash(nextIndex, prevHash, nextTime, data);
return new Block(nextIndex, prevHash, nextHash, nextTime, data);
}

46. MINING BLOCK
public static Block nextBlock(Block prevBlock, Object data) {
int nextIndex = previousBlock.index + 1;
String prevHash = prevBlock.getHash();
long nextTime = new Date().getTime();
String nextHash = calculateHash(nextIndex, prevHash, nextTime, data);
return new Block(nextIndex, prevHash, nextHash, nextTime, data);
}

47. MINING BLOCK
public static Block nextBlock(Block prevBlock, Object data) {
int nextIndex = previousBlock.index + 1;
String prevHash = prevBlock.getHash();
long nextTime = new Date().getTime();
String nextHash = calculateHash(nextIndex, prevHash, nextTime, data);
return new Block(nextIndex, prevHash, nextHash, nextTime, data);
}

48. MINING BLOCK
public static Block nextBlock(Block prevBlock, Object data) {
int nextIndex = previousBlock.index + 1;
String prevHash = prevBlock.getHash();
long nextTime = new Date().getTime();
String nextHash = calculateHash(nextIndex, prevHash, nextTime, data);
return new Block(nextIndex, prevHash, nextHash, nextTime, data);
}

49. CALCULATE HASH
private String calculateHash(int index, String prevHash, long ts, Object data) {
return sha256Hex(index + prevHash + ts + data.hashCode());
}

50. MINING BLOCK
public static Block nextBlock(Block prevBlock, Object data) {
int nextIndex = previousBlock.index + 1;
String prevHash = prevBlock.getHash();
long nextTime = new Date().getTime();
String nextHash = calculateHash(nextIndex, prevHash, nextTime, data);
return new Block(nextIndex, prevHash, nextHash, nextTime, data);
}

51. MINING BLOCK
public class BlockchainService {
Blockchain chain = new Blockchain();
public Block mineBlock(Object data) => {
Block newBlock = nextBlock(chain.getLast(), data);
chain.addBlock(newBlock);
return chain.getLast();
};
}

52. ADDING BLOCK TO CHAIN
public class Blockchain extends LinkedList<Block> {
(...)
public BlockchainResponse addBlock(Block block){
if(isValidNewBlock(getLast(), block)) {
add(block);
}
return new BlockchainResponse(RESPONSE_BLOCKCHAIN, block);
}
(...)
}

53. ADDING BLOCK TO CHAIN
public class Blockchain extends LinkedList<Block> {
(...)
public BlockchainResponse addBlock(Block block){
if(isValidNewBlock(getLast(), block)) {
add(block);
}
return new BlockchainResponse(RESPONSE_BLOCKCHAIN, block);
}
(...)
}

54. BLOCK VALIDATION
public static boolean isValidNewBlock(Block previousBlock, Block newBlock){
if (previousBlock.getIndex() + 1 != newBlock.getIndex()) {
return false;
}
if (!previousBlock.getHash().equals(newBlock.getHash())) {
return false;
}
if (calculateHashForBlock(newBlock).equals(newBlock.getHash())) {
return false;
}
return true;
}

55. BLOCK VALIDATION
public static boolean isValidNewBlock(Block previousBlock, Block newBlock){
if (previousBlock.getIndex() + 1 != newBlock.getIndex()) {
return false;
}
if (!previousBlock.getHash().equals(newBlock.getHash())) {
return false;
}
if (calculateHashForBlock(newBlock).equals(newBlock.getHash())) {
return false;
}
return true;
}

56. BLOCK VALIDATION
public static boolean isValidNewBlock(Block previousBlock, Block newBlock){
if (previousBlock.getIndex() + 1 != newBlock.getIndex()) {
return false;
}
if (!previousBlock.getHash().equals(newBlock.getHash())) {
return false;
}
if (calculateHashForBlock(newBlock).equals(newBlock.getHash())) {
return false;
}
return true;
}

57. BLOCK VALIDATION
public static boolean isValidNewBlock(Block previousBlock, Block newBlock){
if (previousBlock.getIndex() + 1 != newBlock.getIndex()) {
return false;
}
if (!previousBlock.getHash().equals(newBlock.getHash())) {
return false;
}
if (calculateHashForBlock(newBlock).equals(newBlock.getHash())) {
return false;
}
return true;
}

58. ADDING BLOCK TO CHAIN
public class Blockchain extends LinkedList<Block> {
(...)
public BlockchainResponse addBlock(Block block){
if(isValidNewBlock(getLast(), block)) {
add(block);
}
return new BlockchainResponse(RESPONSE_BLOCKCHAIN, block);
}
(...)
}

59. TEXT
Hash #0
Genesis Block
Hash #1
PrevHash #0
Hash #2
PrevHash #1
BLOCKCHAIN

60. ADDING BLOCK TO CHAIN
public class Blockchain extends LinkedList<Block> {
(...)
public Response addBlock(Block block){
if(isValidNewBlock(getLast(), block)) {
add(block);
}
return new Response(RESPONSE_BLOCKCHAIN, block);
}
(...)
}

61. TEXT
New Block
New Block
GOSSIP PROTOCOL

62. NEW BLOCK HANDLING
public Response handleBlockchainResponse(Blockchain newChain) {
if (newChain.getLast().getIndex() > chain.getLast().getIndex()) {
if (chain.getLast().getHash().equals(newChain.getLast().getPreviousHash())){
chain.addBlock(latestBlockReceived);
return new Response(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
}
return exchangeChains(newChain);
}
return new Response(DO_NOTHING);
}

63. NEW BLOCK HANDLING
public Response handleBlockchainResponse(Blockchain newChain) {
if (newChain.getLast().getIndex() > chain.getLast().getIndex()) {
if (chain.getLast().getHash().equals(newChain.getLast().getPreviousHash())){
chain.addBlock(latestBlockReceived);
return new Response(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
}
return exchangeChains(newChain);
}
return new Response(DO_NOTHING);
}

64. NEW BLOCK HANDLING
public Response handleBlockchainResponse(Blockchain newChain) {
if (newChain.getLast().getIndex() > chain.getLast().getIndex()) {
if (chain.getLast().getHash().equals(newChain.getLast().getPreviousHash())){
chain.addBlock(latestBlockReceived);
return new Response(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
}
return exchangeChains(newChain);
}
return new Response(DO_NOTHING);
}

65. NEW BLOCK HANDLING
public Response handleBlockchainResponse(Blockchain newChain) {
if (newChain.getLast().getIndex() > chain.getLast().getIndex()) {
if (chain.getLast().getHash().equals(newChain.getLast().getPreviousHash())){
chain.addBlock(latestBlockReceived);
return new BlockchainResponse(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
}
return exchangeChains(newChain);
}
return new BlockchainResponse(DO_NOTHING);
}

66. TEXT
Hash #2
EXCHANGE CHAINS

67. TEXT
New Chain
New Chain
GOSSIP PROTOCOL

68. REPLACING CHAIN
private Response exchangeChain(Blockchain newBlockchain) {
if (newBlockchain.isValidChain() && newBlockchain.size() > chain.size()) {
chain = newBlockchain;
return new Response(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
} else {
return new Response(DO_NOTHING);
}
}

69. REPLACING CHAIN
private Response exchangeChain(Blockchain newBlockchain) {
if (newBlockchain.isValidChain() && newBlockchain.size() > chain.size()) {
chain = newBlockchain;
return new Response(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
} else {
return new Response(DO_NOTHING);
}
}

70. REPLACING CHAIN
private Response exchangeChain(Blockchain newBlockchain) {
if (newBlockchain.isValidChain() && newBlockchain.size() > chain.size()) {
chain = newBlockchain;
return new Response(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
} else {
return new Response(DO_NOTHING);
}
}

71. VALIDATING CHAIN
public boolean isValidChain(){
if (!this.getFirst().equals(GENESIS_BLOCK)){
return false;
}
for (int i = 1; i < this.size() - 1; i++) {
if (!Block.isValidNewBlock(this.get(i - 1), this.get(i))){
return false;
}
}
return true;
}

72. VALIDATING CHAIN
public boolean isValidChain(){
if (!this.getFirst().equals(GENESIS_BLOCK)){
return false;
}
for (int i = 1; i < this.size() - 1; i++) {
if (!Block.isValidNewBlock(this.get(i - 1), this.get(i))){
return false;
}
}
return true;
}

73. VALIDATING CHAIN
public boolean isValidChain(){
if (!this.getFirst().equals(GENESIS_BLOCK)){
return false;
}
for (int i = 1; i < this.size() - 1; i++) {
if (!Block.isValidNewBlock(this.get(i - 1), this.get(i))){
return false;
}
}
return true;
}

74. REPLACING CHAIN
private Response exchangeChain(Blockchain newBlockchain) {
if (newBlockchain.isValidChain() && newBlockchain.size() > chain.size()) {
chain = newBlockchain;
return new Response(RESPONSE_BLOCKCHAIN, new Blockchain(chain.getLast()));
} else {
return new Response(DO_NOTHING);
}
}

75. TEXT
LONGER HASH WINS

76. TEXT
SPINNING NEW BLOCKS

77. PROOF-OF-WORK

78. PROOF-OF-WORK
private static HashPair calculateHash(int index, String previousHash, Object data) {
int nonce = 0;
while (true) {
nonce++;
String value = sha256Hex(index + previousHash + data.hashCode() + nonce);
if (value.startsWith(“000")) {
return new HashPair(nounce, value);
}
}
}

79. PROOF-OF-WORK
private static HashPair calculateHash(int index, String previousHash, Object data) {
int nonce = 0;
while (true) {
nonce++;
String value = sha256Hex(index + previousHash + data.hashCode() + nonce);
if (value.startsWith(“000")) {
return new HashPair(nounce, value);
}
}
}

80. PROOF-OF-WORK
private static HashPair calculateHash(int index, String previousHash, Object data) {
int nonce = 0;
while (true) {
nonce++;
String value = sha256Hex(index + previousHash + data.hashCode() + nonce);
if (value.startsWith(“000")) {
return new HashPair(nonce, value);
}
}
}

81. PROOF-OF-WORK
private static HashPair calculateHash(int index, String previousHash, Object data) {
int nonce = 0;
while (true) {
nonce++;
String value = sha256Hex(index + previousHash + data.hashCode() + nonce);
if (value.startsWith(“000")) {
return new HashPair(nonce, value);
}
}
}

82. PROOF-OF-WORK
private static HashPair calculateHash(int index, String previousHash, Object data) {
int nonce = 0;
while (true) {
nonce++;
String value = sha256Hex(index + previousHash + data.hashCode() + nonce);
if (value.startsWith(“000")) {
return new HashPair(nonce, value);
}
}
}

83. PROOF-OF-WORK
private static HashPair calculateHash(int index, String previousHash, Object data) {
int nonce = 0;
while (true) {
nonce++;
String value = sha256Hex(index + previousHash + data.hashCode() + nonce);
if (value.startsWith(“000")) {
return new HashPair(nonce, value);
}
}
}

84. PROOF-OF-WORK
private static HashPair calculateHash(int index, String previousHash, Object data) {
int nonce = 0;
while (true) {
nonce++;
String value = sha256Hex(index + previousHash + data.hashCode() + nonce);
if (value.startsWith(“000")) {
return new HashPair(nonce, value);
}
}
}

85. TEXT
IDEAL HASH FUNCTION
f( )
f( )?

86. TEXT
I HAVE HASH! 000004CEEF5782B82C212CE725F15594!
00000ee187308970bb63446f3f910e98000004ceef5782b82c212ce725f15594

87. TEXT
Hash #0 Hash #1 Hash #2
SECURITY
Hash #0
Hash #1
Prev #0
Hash #2
Prev #1
Hash #3
Prev #2
Hash #4
Prev #3
Hash #1x
Hash #2x
Prev #1x
Hash #3x
Prev #2x
FORK

88. ▸ =
50% OF WHOLE NETWORK

89. TEXT
BLOCKCHAIN
Hash #1
Prev #2
Hash #2
Prev #3
Hash #0
Prev #1
Hash #0
$ $ $

90. TEXT
PROBLEMS

91. TEXT
ENVIRONMENTAL UNFRIENDLY

92. TEXT
> ENERGY USAGE ICELAND

93. PROOF-OF-STAKE
PRIMECOIN

94. TEXT
SCALABILITY ISSUES

95. TEXT
VERTICAL SCALING HORIZONTAL SCALING

96. TEXT
VERTICAL SCALING

97. TEXT
HORIZANTAL SCALING

98. PROOF-OF-STAKE
DIRECT ACYCLIC GRAPH
LIGHTNING NETWORKS

99. TEXT
SMART CONTRACTS
INITIAL COIN OFFERINGS
SOFT & HARD FORKS

100. TEXT
DNS
IOT
SMART
CONTRACT

101. TEXT

102. THANK YOU AND
WAITING FOR
QUESTIONS
@ArturSkowronski
arturskowronski.com