From fe8e8211a7fd5b6849c1de0a7219328eb55a44c5 Mon Sep 17 00:00:00 2001 From: oleksii Date: Mon, 19 Nov 2018 00:33:14 +0200 Subject: [PATCH 1/4] First phase implementation done --- src/blockchain/Block.java | 40 +++++++++++++++++++++++++++++++ src/blockchain/Blockchain.java | 44 ++++++++++++++++++++++++++++++++++ src/blockchain/Main.java | 18 ++++++++++++-- src/blockchain/StringUtil.java | 28 ++++++++++++++++++++++ 4 files changed, 128 insertions(+), 2 deletions(-) create mode 100644 src/blockchain/Block.java create mode 100644 src/blockchain/Blockchain.java create mode 100644 src/blockchain/StringUtil.java diff --git a/src/blockchain/Block.java b/src/blockchain/Block.java new file mode 100644 index 0000000..534b357 --- /dev/null +++ b/src/blockchain/Block.java @@ -0,0 +1,40 @@ +package blockchain; + +public class Block { + + private final Integer id; + private final String hashPreviousBlock; + private final String hash; + private final String data; + private final Long timestamp; + + + public Block(Integer id, String hashPreviousBlock, String hash, String data, + Long timestamp) { + this.id = id; + this.hashPreviousBlock = hashPreviousBlock; + this.hash = hash; + this.data = data; + this.timestamp = timestamp; + } + + public Integer getId() { + return id; + } + + public String getHashPreviousBlock() { + return hashPreviousBlock; + } + + public String getHash() { + return hash; + } + + public Long getTimestamp() { + return timestamp; + } + + public String getData() { + return data; + } +} diff --git a/src/blockchain/Blockchain.java b/src/blockchain/Blockchain.java new file mode 100644 index 0000000..39c97f6 --- /dev/null +++ b/src/blockchain/Blockchain.java @@ -0,0 +1,44 @@ +package blockchain; + +import java.util.Collections; +import java.util.Date; +import java.util.Iterator; +import java.util.LinkedList; + +public class Blockchain implements Iterable { + + private final LinkedList blocks; + + public Blockchain() { + blocks = new LinkedList<>(Collections.singleton( + new Block(1, + "0", + StringUtil.applySha256("0" + "pivot"), + "pivot", + new Date().getTime())) + ); + } + + public void generate() { + Long timestamp = new Date().getTime(); + Block tailBlock = blocks.getLast(); + String hash = StringUtil.applySha256(tailBlock.getHash() + "hello"); + blocks.add(new Block(tailBlock.getId() + 1, tailBlock.getHash(), hash, "hello", timestamp)); + } + + public boolean validate() { + for (int i = 1; i < blocks.size(); i++) { + Block prev = blocks.get(i - 1); + Block cur = blocks.get(i); + if (!cur.getHashPreviousBlock().equals(prev.getHash())) { + return false; + } + } + return true; + } + + @Override + public Iterator iterator() { + return blocks.iterator(); + } +} diff --git a/src/blockchain/Main.java b/src/blockchain/Main.java index adf1d02..c44806f 100644 --- a/src/blockchain/Main.java +++ b/src/blockchain/Main.java @@ -1,7 +1,21 @@ package blockchain; public class Main { - public static void main(String[] args) { - System.out.print("Hello world!"); + + public static void main(String[] args) { + Blockchain blockchain = new Blockchain(); + for (int i = 0; i < 10; i++) { + blockchain.generate(); + } + + for (Block block : blockchain) { + System.out.printf("Block:\n"); + System.out.printf("Id: %s\n", block.getId()); + System.out.printf("Timestamp: %s\n", block.getTimestamp()); + System.out.printf("Hash of the previous block:\n%s\n", block.getHashPreviousBlock()); + System.out.printf("Hash of the block: \n%s\n\n", block.getHash()); } + + System.out.println(blockchain.validate()); + } } \ No newline at end of file diff --git a/src/blockchain/StringUtil.java b/src/blockchain/StringUtil.java new file mode 100644 index 0000000..9a4c32d --- /dev/null +++ b/src/blockchain/StringUtil.java @@ -0,0 +1,28 @@ +package blockchain; + +import java.nio.charset.StandardCharsets; +import java.security.MessageDigest; + +public class StringUtil { + + /** + * Applies Sha256 to a string and returns a hash. + */ + public static String applySha256(String input) { + try { + MessageDigest digest = MessageDigest.getInstance("SHA-256"); + byte[] hash = digest.digest(input.getBytes(StandardCharsets.UTF_8)); + StringBuilder hexString = new StringBuilder(); + for (byte elem : hash) { + String hex = Integer.toHexString(0xff & elem); + if (hex.length() == 1) { + hexString.append('0'); + } + hexString.append(hex); + } + return hexString.toString(); + } catch (Exception e) { + throw new RuntimeException(e); + } + } +} From ddac0ff8d02695a247504226c30b9a4293f9054e Mon Sep 17 00:00:00 2001 From: oleksii Date: Tue, 27 Nov 2018 01:04:00 +0200 Subject: [PATCH 2/4] Second phase implementation done --- src/blockchain/Block.java | 12 +++++- src/blockchain/Blockchain.java | 69 +++++++++++++++++++++++++++------- src/blockchain/Main.java | 30 +++++++++------ src/blockchain/Persister.java | 43 +++++++++++++++++++++ 4 files changed, 127 insertions(+), 27 deletions(-) create mode 100644 src/blockchain/Persister.java diff --git a/src/blockchain/Block.java b/src/blockchain/Block.java index 534b357..6b92063 100644 --- a/src/blockchain/Block.java +++ b/src/blockchain/Block.java @@ -1,21 +1,25 @@ package blockchain; -public class Block { +import java.io.Serializable; + +public class Block implements Serializable { private final Integer id; private final String hashPreviousBlock; private final String hash; private final String data; private final Long timestamp; + private final Integer magicNumber; public Block(Integer id, String hashPreviousBlock, String hash, String data, - Long timestamp) { + Long timestamp, Integer magicNumber) { this.id = id; this.hashPreviousBlock = hashPreviousBlock; this.hash = hash; this.data = data; this.timestamp = timestamp; + this.magicNumber = magicNumber; } public Integer getId() { @@ -37,4 +41,8 @@ public Long getTimestamp() { public String getData() { return data; } + + public Integer getMagicNumber() { + return magicNumber; + } } diff --git a/src/blockchain/Blockchain.java b/src/blockchain/Blockchain.java index 39c97f6..c38e05d 100644 --- a/src/blockchain/Blockchain.java +++ b/src/blockchain/Blockchain.java @@ -4,29 +4,63 @@ import java.util.Date; import java.util.Iterator; import java.util.LinkedList; +import java.util.List; +import java.util.Random; +import java.util.stream.Stream; public class Blockchain implements Iterable { private final LinkedList blocks; + private final Random random; + private final String prefix; + private final Persister persister; - public Blockchain() { - blocks = new LinkedList<>(Collections.singleton( - new Block(1, - "0", - StringUtil.applySha256("0" + "pivot"), - "pivot", - new Date().getTime())) - ); + public Blockchain(int N) { + persister = new Persister("blockchain.ser"); + random = new Random(); + prefix = Stream.iterate("0", x -> "0").limit(N).reduce("", (x, y) -> x + y); + if (persister.existsChain()) { + LinkedList blocks = (LinkedList) persister.load(); + if (validate(blocks)) { + this.blocks = blocks; + } else { + Block firstBlock = initialBlockHead(); + this.blocks = new LinkedList<>(Collections.singleton(firstBlock)); + } + } else { + Block firstBlock = initialBlockHead(); + blocks = new LinkedList<>(Collections.singleton(firstBlock)); + } + persister.save(blocks); } + public void generate() { Long timestamp = new Date().getTime(); Block tailBlock = blocks.getLast(); - String hash = StringUtil.applySha256(tailBlock.getHash() + "hello"); - blocks.add(new Block(tailBlock.getId() + 1, tailBlock.getHash(), hash, "hello", timestamp)); + Integer magicNumber = random.nextInt(); + String hash = StringUtil.applySha256(tailBlock.getHash() + "hello" + magicNumber); + while (!hash.startsWith(prefix)) { + magicNumber = random.nextInt(); + hash = StringUtil.applySha256(tailBlock.getHash() + "hello" + magicNumber); + } + + Block newBlock = new Block(tailBlock.getId() + 1, tailBlock.getHash(), hash, "hello", timestamp, + magicNumber); + blocks.add(newBlock); + persister.save(blocks); } public boolean validate() { + return validate(blocks); + } + + @Override + public Iterator iterator() { + return blocks.iterator(); + } + + private boolean validate(List blocks) { for (int i = 1; i < blocks.size(); i++) { Block prev = blocks.get(i - 1); Block cur = blocks.get(i); @@ -37,8 +71,17 @@ public boolean validate() { return true; } - @Override - public Iterator iterator() { - return blocks.iterator(); + private Block initialBlockHead() { + Integer magicNumber = random.nextInt(); + String hash = StringUtil.applySha256("0" + magicNumber); + while (!hash.startsWith(prefix)) { + magicNumber = random.nextInt(); + hash = StringUtil.applySha256("0" + magicNumber); + } + return new Block(1, + "0", + hash, + "empty", + new Date().getTime(), magicNumber); } } diff --git a/src/blockchain/Main.java b/src/blockchain/Main.java index c44806f..d67a9ad 100644 --- a/src/blockchain/Main.java +++ b/src/blockchain/Main.java @@ -1,21 +1,27 @@ package blockchain; +import java.util.Scanner; + public class Main { public static void main(String[] args) { - Blockchain blockchain = new Blockchain(); - for (int i = 0; i < 10; i++) { - blockchain.generate(); - } + try (Scanner scanner = new Scanner(System.in)) { + System.out.printf("Enter how many zeros the hash must starts with: "); + Blockchain blockchain = new Blockchain(scanner.nextInt()); + for (int i = 0; i < 10; i++) { + blockchain.generate(); + } - for (Block block : blockchain) { - System.out.printf("Block:\n"); - System.out.printf("Id: %s\n", block.getId()); - System.out.printf("Timestamp: %s\n", block.getTimestamp()); - System.out.printf("Hash of the previous block:\n%s\n", block.getHashPreviousBlock()); - System.out.printf("Hash of the block: \n%s\n\n", block.getHash()); - } + for (Block block : blockchain) { + System.out.printf("Block:\n"); + System.out.printf("Id: %s\n", block.getId()); + System.out.printf("Timestamp: %s\n", block.getTimestamp()); + System.out.printf("Magic number: %s\n", block.getMagicNumber()); + System.out.printf("Hash of the previous block:\n%s\n", block.getHashPreviousBlock()); + System.out.printf("Hash of the block: \n%s\n\n", block.getHash()); + } - System.out.println(blockchain.validate()); + System.out.println(blockchain.validate()); + } } } \ No newline at end of file diff --git a/src/blockchain/Persister.java b/src/blockchain/Persister.java new file mode 100644 index 0000000..7b67c12 --- /dev/null +++ b/src/blockchain/Persister.java @@ -0,0 +1,43 @@ +package blockchain; + +import java.io.FileInputStream; +import java.io.FileOutputStream; +import java.io.IOException; +import java.io.ObjectInputStream; +import java.io.ObjectOutputStream; +import java.nio.file.Files; +import java.nio.file.Paths; +import java.util.List; + +public class Persister { + + + private String filename; + + public Persister(String filename) { + this.filename = filename; + } + + public void save(List blockchain) { + try (FileOutputStream fileOutputStream = new FileOutputStream(filename); + ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream)) { + objectOutputStream.writeObject(blockchain); + } catch (IOException e) { + e.printStackTrace(); + } + } + + public List load() { + try (FileInputStream fileInputStream = new FileInputStream(filename); + ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream)) { + return (List) objectInputStream.readObject(); + } catch (IOException | ClassNotFoundException e) { + e.printStackTrace(); + } + return null; + } + + public boolean existsChain() { + return Files.exists(Paths.get(filename)); + } +} From 7078dffbfbd4f7657a613f61779d9533524e038f Mon Sep 17 00:00:00 2001 From: oleksii Date: Mon, 3 Dec 2018 00:46:23 +0200 Subject: [PATCH 3/4] Second phase implementation done --- src/blockchain/Block.java | 8 +++- src/blockchain/Blockchain.java | 64 ++++++++++++------------------- src/blockchain/FilePersister.java | 47 +++++++++++++++++++++++ src/blockchain/Main.java | 13 +++++-- src/blockchain/Persister.java | 40 ++----------------- 5 files changed, 92 insertions(+), 80 deletions(-) create mode 100644 src/blockchain/FilePersister.java diff --git a/src/blockchain/Block.java b/src/blockchain/Block.java index 6b92063..ec7c110 100644 --- a/src/blockchain/Block.java +++ b/src/blockchain/Block.java @@ -10,16 +10,18 @@ public class Block implements Serializable { private final String data; private final Long timestamp; private final Integer magicNumber; + private final Long generationTime; public Block(Integer id, String hashPreviousBlock, String hash, String data, - Long timestamp, Integer magicNumber) { + Long timestamp, Integer magicNumber, Long generationTime) { this.id = id; this.hashPreviousBlock = hashPreviousBlock; this.hash = hash; this.data = data; this.timestamp = timestamp; this.magicNumber = magicNumber; + this.generationTime = generationTime; } public Integer getId() { @@ -45,4 +47,8 @@ public String getData() { public Integer getMagicNumber() { return magicNumber; } + + public Long getGenerationTime() { + return generationTime; + } } diff --git a/src/blockchain/Blockchain.java b/src/blockchain/Blockchain.java index c38e05d..83ff3f0 100644 --- a/src/blockchain/Blockchain.java +++ b/src/blockchain/Blockchain.java @@ -1,7 +1,6 @@ package blockchain; import java.util.Collections; -import java.util.Date; import java.util.Iterator; import java.util.LinkedList; import java.util.List; @@ -10,43 +9,32 @@ public class Blockchain implements Iterable { - private final LinkedList blocks; + private final List blocks; private final Random random; private final String prefix; private final Persister persister; - public Blockchain(int N) { - persister = new Persister("blockchain.ser"); - random = new Random(); - prefix = Stream.iterate("0", x -> "0").limit(N).reduce("", (x, y) -> x + y); - if (persister.existsChain()) { - LinkedList blocks = (LinkedList) persister.load(); - if (validate(blocks)) { - this.blocks = blocks; - } else { - Block firstBlock = initialBlockHead(); - this.blocks = new LinkedList<>(Collections.singleton(firstBlock)); - } + public Blockchain(int N, Persister persister) { + this.persister = persister; + this.random = new Random(); + this.prefix = Stream.iterate("0", x -> "0") + .limit(N) + .reduce("", (x, y) -> x + y); + + List blocks = persister.load(); + if (!blocks.isEmpty() && validate(blocks)) { + this.blocks = blocks; } else { - Block firstBlock = initialBlockHead(); - blocks = new LinkedList<>(Collections.singleton(firstBlock)); + this.blocks = new LinkedList<>(Collections.singleton( + generateNextBlock(1, "0", "empty"))); + persister.save(blocks); } - persister.save(blocks); } public void generate() { - Long timestamp = new Date().getTime(); - Block tailBlock = blocks.getLast(); - Integer magicNumber = random.nextInt(); - String hash = StringUtil.applySha256(tailBlock.getHash() + "hello" + magicNumber); - while (!hash.startsWith(prefix)) { - magicNumber = random.nextInt(); - hash = StringUtil.applySha256(tailBlock.getHash() + "hello" + magicNumber); - } - - Block newBlock = new Block(tailBlock.getId() + 1, tailBlock.getHash(), hash, "hello", timestamp, - magicNumber); + Block tailBlock = blocks.get(blocks.size() - 1); + Block newBlock = generateNextBlock(tailBlock.getId() + 1, tailBlock.getHash(), "hello"); blocks.add(newBlock); persister.save(blocks); } @@ -71,17 +59,15 @@ private boolean validate(List blocks) { return true; } - private Block initialBlockHead() { - Integer magicNumber = random.nextInt(); - String hash = StringUtil.applySha256("0" + magicNumber); - while (!hash.startsWith(prefix)) { + private Block generateNextBlock(int id, String hashPreviousBlock, String data) { + long timestamp = System.currentTimeMillis(); + Integer magicNumber; + String hash; + do { magicNumber = random.nextInt(); - hash = StringUtil.applySha256("0" + magicNumber); - } - return new Block(1, - "0", - hash, - "empty", - new Date().getTime(), magicNumber); + hash = StringUtil.applySha256(hashPreviousBlock + magicNumber); + } while (!hash.startsWith(prefix)); + return new Block(id, hashPreviousBlock, hash, data, timestamp, magicNumber, + System.currentTimeMillis() - timestamp); } } diff --git a/src/blockchain/FilePersister.java b/src/blockchain/FilePersister.java new file mode 100644 index 0000000..2b08d9e --- /dev/null +++ b/src/blockchain/FilePersister.java @@ -0,0 +1,47 @@ +package blockchain; + +import java.io.FileInputStream; +import java.io.FileOutputStream; +import java.io.IOException; +import java.io.ObjectInputStream; +import java.io.ObjectOutputStream; +import java.nio.file.Files; +import java.nio.file.Paths; +import java.util.List; + +class FilePersister implements Persister { + + + private final String filename; + + public FilePersister(String filename) { + this.filename = filename; + } + + @Override + public void save(List blockchain) { + try (FileOutputStream fileOutputStream = new FileOutputStream(filename); + ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream)) { + objectOutputStream.writeObject(blockchain); + } catch (IOException e) { + throw new RuntimeException(); + } + } + + @Override + public List load() { + if (fileExists()) { + try (FileInputStream fileInputStream = new FileInputStream(filename); + ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream)) { + return (List) objectInputStream.readObject(); + } catch (IOException | ClassNotFoundException e) { + return List.of(); + } + } + return List.of(); + } + + private boolean fileExists() { + return Files.exists(Paths.get(filename)); + } +} diff --git a/src/blockchain/Main.java b/src/blockchain/Main.java index d67a9ad..492d299 100644 --- a/src/blockchain/Main.java +++ b/src/blockchain/Main.java @@ -6,8 +6,11 @@ public class Main { public static void main(String[] args) { try (Scanner scanner = new Scanner(System.in)) { - System.out.printf("Enter how many zeros the hash must starts with: "); - Blockchain blockchain = new Blockchain(scanner.nextInt()); + System.out.print("Enter how many zeros the hash must starts with: "); + + Persister persister = new FilePersister("blockchain.ser"); + Blockchain blockchain = new Blockchain(scanner.nextInt(), persister); + for (int i = 0; i < 10; i++) { blockchain.generate(); } @@ -18,10 +21,12 @@ public static void main(String[] args) { System.out.printf("Timestamp: %s\n", block.getTimestamp()); System.out.printf("Magic number: %s\n", block.getMagicNumber()); System.out.printf("Hash of the previous block:\n%s\n", block.getHashPreviousBlock()); - System.out.printf("Hash of the block: \n%s\n\n", block.getHash()); + System.out.printf("Hash of the block: \n%s\n", block.getHash()); + System.out + .printf("Block was generating for: %s seconds\n\n", block.getGenerationTime() / 1000); } - System.out.println(blockchain.validate()); + System.out.printf("Valid: %s\n", blockchain.validate()); } } } \ No newline at end of file diff --git a/src/blockchain/Persister.java b/src/blockchain/Persister.java index 7b67c12..fe58027 100644 --- a/src/blockchain/Persister.java +++ b/src/blockchain/Persister.java @@ -1,43 +1,11 @@ package blockchain; -import java.io.FileInputStream; -import java.io.FileOutputStream; -import java.io.IOException; -import java.io.ObjectInputStream; -import java.io.ObjectOutputStream; -import java.nio.file.Files; -import java.nio.file.Paths; import java.util.List; -public class Persister { +public interface Persister { + void save(List blockchain); - private String filename; - - public Persister(String filename) { - this.filename = filename; - } - - public void save(List blockchain) { - try (FileOutputStream fileOutputStream = new FileOutputStream(filename); - ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream)) { - objectOutputStream.writeObject(blockchain); - } catch (IOException e) { - e.printStackTrace(); - } - } - - public List load() { - try (FileInputStream fileInputStream = new FileInputStream(filename); - ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream)) { - return (List) objectInputStream.readObject(); - } catch (IOException | ClassNotFoundException e) { - e.printStackTrace(); - } - return null; - } - - public boolean existsChain() { - return Files.exists(Paths.get(filename)); - } + List load(); } + From 307661d321f0a3795bda52fc70333ced2a36e605 Mon Sep 17 00:00:00 2001 From: oleksii Date: Sat, 15 Dec 2018 16:31:03 +0200 Subject: [PATCH 4/4] Second phase implementation done --- src/blockchain/Block.java | 8 +------- src/blockchain/Blockchain.java | 8 ++++---- src/blockchain/Main.java | 2 -- 3 files changed, 5 insertions(+), 13 deletions(-) diff --git a/src/blockchain/Block.java b/src/blockchain/Block.java index ec7c110..3721027 100644 --- a/src/blockchain/Block.java +++ b/src/blockchain/Block.java @@ -7,18 +7,16 @@ public class Block implements Serializable { private final Integer id; private final String hashPreviousBlock; private final String hash; - private final String data; private final Long timestamp; private final Integer magicNumber; private final Long generationTime; - public Block(Integer id, String hashPreviousBlock, String hash, String data, + public Block(Integer id, String hashPreviousBlock, String hash, Long timestamp, Integer magicNumber, Long generationTime) { this.id = id; this.hashPreviousBlock = hashPreviousBlock; this.hash = hash; - this.data = data; this.timestamp = timestamp; this.magicNumber = magicNumber; this.generationTime = generationTime; @@ -40,10 +38,6 @@ public Long getTimestamp() { return timestamp; } - public String getData() { - return data; - } - public Integer getMagicNumber() { return magicNumber; } diff --git a/src/blockchain/Blockchain.java b/src/blockchain/Blockchain.java index 83ff3f0..a372326 100644 --- a/src/blockchain/Blockchain.java +++ b/src/blockchain/Blockchain.java @@ -26,7 +26,7 @@ public Blockchain(int N, Persister persister) { this.blocks = blocks; } else { this.blocks = new LinkedList<>(Collections.singleton( - generateNextBlock(1, "0", "empty"))); + generateNextBlock(1, "0"))); persister.save(blocks); } } @@ -34,7 +34,7 @@ public Blockchain(int N, Persister persister) { public void generate() { Block tailBlock = blocks.get(blocks.size() - 1); - Block newBlock = generateNextBlock(tailBlock.getId() + 1, tailBlock.getHash(), "hello"); + Block newBlock = generateNextBlock(tailBlock.getId() + 1, tailBlock.getHash()); blocks.add(newBlock); persister.save(blocks); } @@ -59,7 +59,7 @@ private boolean validate(List blocks) { return true; } - private Block generateNextBlock(int id, String hashPreviousBlock, String data) { + private Block generateNextBlock(int id, String hashPreviousBlock) { long timestamp = System.currentTimeMillis(); Integer magicNumber; String hash; @@ -67,7 +67,7 @@ private Block generateNextBlock(int id, String hashPreviousBlock, String data) { magicNumber = random.nextInt(); hash = StringUtil.applySha256(hashPreviousBlock + magicNumber); } while (!hash.startsWith(prefix)); - return new Block(id, hashPreviousBlock, hash, data, timestamp, magicNumber, + return new Block(id, hashPreviousBlock, hash, timestamp, magicNumber, System.currentTimeMillis() - timestamp); } } diff --git a/src/blockchain/Main.java b/src/blockchain/Main.java index 492d299..e7db2ea 100644 --- a/src/blockchain/Main.java +++ b/src/blockchain/Main.java @@ -25,8 +25,6 @@ public static void main(String[] args) { System.out .printf("Block was generating for: %s seconds\n\n", block.getGenerationTime() / 1000); } - - System.out.printf("Valid: %s\n", blockchain.validate()); } } } \ No newline at end of file