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Blockchain!

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Steven Tracey 2021-11-21 20:35:10 -05:00
commit 763c968a72
20 changed files with 1015 additions and 0 deletions
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154
.gitignore vendored Normal file
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# ---> Gradle
.gradle
build/
!src/**/build/
!**/src/main/**/build/
!**/src/test/**/build/
!**/src/main/**/bin/
!**/src/test/**/bin/
bin/
# Ignore Gradle GUI config
gradle-app.setting
# Avoid ignoring Gradle wrapper jar file (.jar files are usually ignored)
!gradle-wrapper.jar
# Cache of project
.gradletasknamecache
# ---> Java
# Compiled class file
*.class
# Log file
*.log
# BlueJ files
*.ctxt
# Mobile Tools for Java (J2ME)
.mtj.tmp/
# Package Files #
*.jar
*.war
*.nar
*.ear
*.zip
*.tar.gz
*.rar
# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
hs_err_pid*
# ---> JetBrains
# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
# User-specific stuff
.idea/**/workspace.xml
.idea/**/tasks.xml
.idea/**/usage.statistics.xml
.idea/**/dictionaries
.idea/**/shelf
# AWS User-specific
.idea/**/aws.xml
# Generated files
.idea/**/contentModel.xml
# Sensitive or high-churn files
.idea/**/dataSources/
.idea/**/dataSources.ids
.idea/**/dataSources.local.xml
.idea/**/sqlDataSources.xml
.idea/**/dynamic.xml
.idea/**/uiDesigner.xml
.idea/**/dbnavigator.xml
# Gradle
.idea/**/gradle.xml
.idea/**/libraries
# Gradle and Maven with auto-import
# When using Gradle or Maven with auto-import, you should exclude module files,
# since they will be recreated, and may cause churn. Uncomment if using
# auto-import.
# .idea/artifacts
# .idea/compiler.xml
# .idea/jarRepositories.xml
# .idea/modules.xml
# .idea/*.iml
# .idea/modules
# *.iml
# *.ipr
# CMake
cmake-build-*/
# Mongo Explorer plugin
.idea/**/mongoSettings.xml
# File-based project format
*.iws
# IntelliJ
out/
# mpeltonen/sbt-idea plugin
.idea_modules/
# JIRA plugin
atlassian-ide-plugin.xml
# Cursive Clojure plugin
.idea/replstate.xml
# Crashlytics plugin (for Android Studio and IntelliJ)
com_crashlytics_export_strings.xml
crashlytics.properties
crashlytics-build.properties
fabric.properties
# Editor-based Rest Client
.idea/httpRequests
# Android studio 3.1+ serialized cache file
.idea/caches/build_file_checksums.ser
# ---> Windows
# Windows thumbnail cache files
Thumbs.db
Thumbs.db:encryptable
ehthumbs.db
ehthumbs_vista.db
# Dump file
*.stackdump
# Folder config file
[Dd]esktop.ini
# Recycle Bin used on file shares
$RECYCLE.BIN/
# Windows Installer files
*.cab
*.msi
*.msix
*.msm
*.msp
# Windows shortcuts
*.lnk
### STS ###
.apt_generated
.classpath
.factorypath
.project
.settings
.springBeans
.sts4-cache

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# Default ignored files
/shelf/
/workspace.xml
# Editor-based HTTP Client requests
/httpRequests/
# Datasource local storage ignored files
/dataSources/
/dataSources.local.xml

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<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
<component name="CompilerConfiguration">
<bytecodeTargetLevel target="11" />
</component>
</project>

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.idea/jarRepositories.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
<component name="RemoteRepositoriesConfiguration">
<remote-repository>
<option name="id" value="central" />
<option name="name" value="Maven Central repository" />
<option name="url" value="https://repo1.maven.org/maven2" />
</remote-repository>
<remote-repository>
<option name="id" value="jboss.community" />
<option name="name" value="JBoss Community repository" />
<option name="url" value="https://repository.jboss.org/nexus/content/repositories/public/" />
</remote-repository>
<remote-repository>
<option name="id" value="MavenRepo" />
<option name="name" value="MavenRepo" />
<option name="url" value="https://repo.maven.apache.org/maven2/" />
</remote-repository>
</component>
</project>

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.idea/misc.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
<component name="ExternalStorageConfigurationManager" enabled="true" />
<component name="FrameworkDetectionExcludesConfiguration">
<file type="web" url="file://$PROJECT_DIR$" />
</component>
<component name="ProjectRootManager" version="2" languageLevel="JDK_11" project-jdk-name="openjdk-17" project-jdk-type="JavaSDK">
<output url="file://$PROJECT_DIR$/out" />
</component>
</project>

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.idea/runConfigurations.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
<component name="RunConfigurationProducerService">
<option name="ignoredProducers">
<set>
<option value="com.android.tools.idea.compose.preview.runconfiguration.ComposePreviewRunConfigurationProducer" />
</set>
</option>
</component>
</project>

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.idea/vcs.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
<component name="VcsDirectoryMappings">
<mapping directory="$PROJECT_DIR$" vcs="Git" />
</component>
</project>

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# NevCoin
Personal Blockchain!

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build.gradle Normal file
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plugins {
id 'java'
id 'org.springframework.boot' version '2.6.0'
id 'io.spring.dependency-management' version '1.0.11.RELEASE'
}
group 'tech.nevets'
version '1.0'
repositories {
mavenCentral()
}
dependencies {
implementation 'com.google.code.gson:gson:2.8.9'
implementation group: 'org.bouncycastle', name: 'bcprov-jdk15on', version: '1.52'
implementation 'org.springframework.boot:spring-boot-starter'
}

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distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-7.1-bin.zip
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists

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#!/usr/bin/env sh
#
# Copyright 2015 the original author or authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
##############################################################################
##
## Gradle start up script for UN*X
##
##############################################################################
# Attempt to set APP_HOME
# Resolve links: $0 may be a link
PRG="$0"
# Need this for relative symlinks.
while [ -h "$PRG" ] ; do
ls=`ls -ld "$PRG"`
link=`expr "$ls" : '.*-> \(.*\)$'`
if expr "$link" : '/.*' > /dev/null; then
PRG="$link"
else
PRG=`dirname "$PRG"`"/$link"
fi
done
SAVED="`pwd`"
cd "`dirname \"$PRG\"`/" >/dev/null
APP_HOME="`pwd -P`"
cd "$SAVED" >/dev/null
APP_NAME="Gradle"
APP_BASE_NAME=`basename "$0"`
# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
# Use the maximum available, or set MAX_FD != -1 to use that value.
MAX_FD="maximum"
warn () {
echo "$*"
}
die () {
echo
echo "$*"
echo
exit 1
}
# OS specific support (must be 'true' or 'false').
cygwin=false
msys=false
darwin=false
nonstop=false
case "`uname`" in
CYGWIN* )
cygwin=true
;;
Darwin* )
darwin=true
;;
MSYS* | MINGW* )
msys=true
;;
NONSTOP* )
nonstop=true
;;
esac
CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
# Determine the Java command to use to start the JVM.
if [ -n "$JAVA_HOME" ] ; then
if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
# IBM's JDK on AIX uses strange locations for the executables
JAVACMD="$JAVA_HOME/jre/sh/java"
else
JAVACMD="$JAVA_HOME/bin/java"
fi
if [ ! -x "$JAVACMD" ] ; then
die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi
else
JAVACMD="java"
which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
fi
# Increase the maximum file descriptors if we can.
if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
MAX_FD_LIMIT=`ulimit -H -n`
if [ $? -eq 0 ] ; then
if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
MAX_FD="$MAX_FD_LIMIT"
fi
ulimit -n $MAX_FD
if [ $? -ne 0 ] ; then
warn "Could not set maximum file descriptor limit: $MAX_FD"
fi
else
warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
fi
fi
# For Darwin, add options to specify how the application appears in the dock
if $darwin; then
GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
fi
# For Cygwin or MSYS, switch paths to Windows format before running java
if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
APP_HOME=`cygpath --path --mixed "$APP_HOME"`
CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
JAVACMD=`cygpath --unix "$JAVACMD"`
# We build the pattern for arguments to be converted via cygpath
ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
SEP=""
for dir in $ROOTDIRSRAW ; do
ROOTDIRS="$ROOTDIRS$SEP$dir"
SEP="|"
done
OURCYGPATTERN="(^($ROOTDIRS))"
# Add a user-defined pattern to the cygpath arguments
if [ "$GRADLE_CYGPATTERN" != "" ] ; then
OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
fi
# Now convert the arguments - kludge to limit ourselves to /bin/sh
i=0
for arg in "$@" ; do
CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
CHECK2=`echo "$arg"|egrep -c "^-"` ### Determine if an option
if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then ### Added a condition
eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
else
eval `echo args$i`="\"$arg\""
fi
i=`expr $i + 1`
done
case $i in
0) set -- ;;
1) set -- "$args0" ;;
2) set -- "$args0" "$args1" ;;
3) set -- "$args0" "$args1" "$args2" ;;
4) set -- "$args0" "$args1" "$args2" "$args3" ;;
5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
esac
fi
# Escape application args
save () {
for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
echo " "
}
APP_ARGS=`save "$@"`
# Collect all arguments for the java command, following the shell quoting and substitution rules
eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
exec "$JAVACMD" "$@"

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@rem
@rem Copyright 2015 the original author or authors.
@rem
@rem Licensed under the Apache License, Version 2.0 (the "License");
@rem you may not use this file except in compliance with the License.
@rem You may obtain a copy of the License at
@rem
@rem https://www.apache.org/licenses/LICENSE-2.0
@rem
@rem Unless required by applicable law or agreed to in writing, software
@rem distributed under the License is distributed on an "AS IS" BASIS,
@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@rem See the License for the specific language governing permissions and
@rem limitations under the License.
@rem
@if "%DEBUG%" == "" @echo off
@rem ##########################################################################
@rem
@rem Gradle startup script for Windows
@rem
@rem ##########################################################################
@rem Set local scope for the variables with windows NT shell
if "%OS%"=="Windows_NT" setlocal
set DIRNAME=%~dp0
if "%DIRNAME%" == "" set DIRNAME=.
set APP_BASE_NAME=%~n0
set APP_HOME=%DIRNAME%
@rem Resolve any "." and ".." in APP_HOME to make it shorter.
for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
@rem Find java.exe
if defined JAVA_HOME goto findJavaFromJavaHome
set JAVA_EXE=java.exe
%JAVA_EXE% -version >NUL 2>&1
if "%ERRORLEVEL%" == "0" goto execute
echo.
echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
echo.
echo Please set the JAVA_HOME variable in your environment to match the
echo location of your Java installation.
goto fail
:findJavaFromJavaHome
set JAVA_HOME=%JAVA_HOME:"=%
set JAVA_EXE=%JAVA_HOME%/bin/java.exe
if exist "%JAVA_EXE%" goto execute
echo.
echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
echo.
echo Please set the JAVA_HOME variable in your environment to match the
echo location of your Java installation.
goto fail
:execute
@rem Setup the command line
set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
@rem Execute Gradle
"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
:end
@rem End local scope for the variables with windows NT shell
if "%ERRORLEVEL%"=="0" goto mainEnd
:fail
rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
rem the _cmd.exe /c_ return code!
if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
exit /b 1
:mainEnd
if "%OS%"=="Windows_NT" endlocal
:omega

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rootProject.name = 'NevCoin'

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src/main/java/tech/nevets/nevcoin/Block.java Normal file
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package tech.nevets.nevcoin;
import tech.nevets.nevcoin.transactions.Transaction;
import tech.nevets.nevcoin.util.StringUtil;
import java.util.ArrayList;
import java.util.Date;
public class Block {
public String hash;
public String previousHash;
public String merkleRoot;
public ArrayList<Transaction> transactions = new ArrayList<Transaction>();
//private String data;
private long timeStamp;
private int nonce;
public Block(String previousHash) {
//this.data = data;
this.previousHash = previousHash;
this.timeStamp = new Date().getTime();
this.hash = calculateHash();
}
public String calculateHash() {
String calculatedHash = StringUtil.applySha256(
previousHash
+ Long.toString(timeStamp)
+ Integer.toString(nonce)
+ merkleRoot
//+ data
);
return calculatedHash;
}
public void mineBlock(int difficulty) {
merkleRoot = StringUtil.getMerkleRoot(transactions);
String target = StringUtil.getDifficultyString(difficulty);
while (!hash.substring(0, difficulty).equals(target)) {
nonce ++;
hash = calculateHash();
}
System.out.println("Block mined: " + hash);
}
public boolean addTransaction(Transaction transaction) {
if (transaction == null) return false;
if (!"0".equals(previousHash)) {
if (transaction.processTransaction() != true) {
System.out.println("Transaction failed to process. Discarded.");
return false;
}
}
transactions.add(transaction);
System.out.println("Transaction Successfully added to Block");
return true;
}
}

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src/main/java/tech/nevets/nevcoin/NevCoin.java Normal file
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package tech.nevets.nevcoin;
import tech.nevets.nevcoin.transactions.Transaction;
import tech.nevets.nevcoin.transactions.TransactionInput;
import tech.nevets.nevcoin.transactions.TransactionOutput;
import java.security.Security;
import java.util.ArrayList;
import java.util.HashMap;
public class NevCoin {
public static ArrayList<Block> blockChain = new ArrayList<Block>();
public static HashMap<String, TransactionOutput> UTXOs = new HashMap<String, TransactionOutput>();
public static int difficulty = 10;
public static float minimumTransaction = 0.1f;
public static Wallet walletA;
public static Wallet walletB;
public static Transaction genesisTransaction;
public static void main(String[] args) {
Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
walletA = new Wallet();
walletB = new Wallet();
Wallet coinbase = new Wallet();
genesisTransaction = new Transaction(coinbase.publicKey, walletA.publicKey, 100f, null);
genesisTransaction.generateSignature(coinbase.privateKey);
genesisTransaction.transactionId = "0";
genesisTransaction.outputs.add(new TransactionOutput(genesisTransaction.recipient, genesisTransaction.value, genesisTransaction.transactionId));
UTXOs.put(genesisTransaction.outputs.get(0).id, genesisTransaction.outputs.get(0));
System.out.println("Creating and Mining Genesis block... ");
Block genesis = new Block("0");
genesis.addTransaction(genesisTransaction);
addBlock(genesis);
Block block1 = new Block(genesis.hash);
System.out.println("\nWalletA's balance is: " + walletA.getBalance());
System.out.println("\nWalletA is Attempting to send funds (40) to WalletB...");
block1.addTransaction(walletA.sendFunds(walletB.publicKey, 40f));
addBlock(block1);
System.out.println("\nWalletA's balance is: " + walletA.getBalance());
System.out.println("WalletB's balance is: " + walletB.getBalance());
Block block2 = new Block(block1.hash);
System.out.println("\nWalletA Attempting to send more funds (1000) than it has...");
block2.addTransaction(walletA.sendFunds(walletB.publicKey, 1000f));
addBlock(block2);
System.out.println("\nWalletA's balance is: " + walletA.getBalance());
System.out.println("WalletB's balance is: " + walletB.getBalance());
Block block3 = new Block(block2.hash);
System.out.println("\nWalletB is Attempting to send funds (20) to WalletA...");
block3.addTransaction(walletB.sendFunds( walletA.publicKey, 20));
System.out.println("\nWalletA's balance is: " + walletA.getBalance());
System.out.println("WalletB's balance is: " + walletB.getBalance());
isChainValid();
}
public static Boolean isChainValid() {
Block currentBlock;
Block previousBlock;
String hashTarget = new String(new char[difficulty]).replace('\0', '0');
HashMap<String,TransactionOutput> tempUTXOs = new HashMap<String,TransactionOutput>();
tempUTXOs.put(genesisTransaction.outputs.get(0).id, genesisTransaction.outputs.get(0));
for (int i = 1; i < blockChain.size(); i++) {
currentBlock = blockChain.get(i);
previousBlock = blockChain.get(i - 1);
if (!currentBlock.hash.equals(currentBlock.calculateHash())) {
System.out.println("Current Hashes not equal");
return false;
}
if (!previousBlock.hash.equals(currentBlock.previousHash)) {
System.out.println("Previous Hashes not equal");
return false;
}
if (!currentBlock.hash.substring(0, difficulty).equals(hashTarget)) {
System.out.println("This block hasn't been mined");
return false;
}
TransactionOutput tempOutput;
for (int t = 0; t < currentBlock.transactions.size(); t++) {
Transaction currentTransaction = currentBlock.transactions.get(t);
if (!currentTransaction.verifySignature()) {
System.out.println("#Signature on Transaction(" + t + ") is Invalid");
return false;
}
if (currentTransaction.getInputsValue() != currentTransaction.getOutputsValue()) {
System.out.println("#Inputs are note equal to outputs on Transaction(" + t + ")");
return false;
}
for (TransactionInput input: currentTransaction.inputs) {
tempOutput = tempUTXOs.get(input.transactionOutputId);
if (tempOutput == null) {
System.out.println("#Referenced input on Transaction(" + t + ") is Missing");
return false;
}
if (input.UTXO.value != tempOutput.value) {
System.out.println("#Referenced input Transaction(" + t + ") value is Invalid");
return false;
}
tempUTXOs.remove(input.transactionOutputId);
}
for (TransactionOutput output: currentTransaction.outputs) {
tempUTXOs.put(output.id, output);
}
if (currentTransaction.outputs.get(0).recipient != currentTransaction.recipient) {
System.out.println("#Transaction(" + t + ") output recipient is not who it should be");
return false;
}
if (currentTransaction.outputs.get(1).recipient != currentTransaction.sender) {
System.out.println("#Transaction(" + t + ") output 'change' is not sender.");
return false;
}
}
}
return true;
}
public static void addBlock(Block newBlock) {
newBlock.mineBlock(difficulty);
blockChain.add(newBlock);
}
}

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src/main/java/tech/nevets/nevcoin/Wallet.java Normal file
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package tech.nevets.nevcoin;
import tech.nevets.nevcoin.transactions.Transaction;
import tech.nevets.nevcoin.transactions.TransactionInput;
import tech.nevets.nevcoin.transactions.TransactionOutput;
import java.security.*;
import java.security.spec.ECGenParameterSpec;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
public class Wallet {
public PrivateKey privateKey;
public PublicKey publicKey;
public HashMap<String, TransactionOutput> UTXOs = new HashMap<String, TransactionOutput>();
public Wallet() {
generateKeyPair();
}
public void generateKeyPair() {
try {
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("ECDSA", "BC");
SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
ECGenParameterSpec ecSpec = new ECGenParameterSpec("prime192v1");
keyGen.initialize(ecSpec, random);
KeyPair keyPair = keyGen.generateKeyPair();
privateKey = keyPair.getPrivate();
publicKey = keyPair.getPublic();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
public float getBalance() {
float total = 0;
for (Map.Entry<String, TransactionOutput> item: NevCoin.UTXOs.entrySet()) {
TransactionOutput UTXO = item.getValue();
if (UTXO.isMine(publicKey)) {
UTXOs.put(UTXO.id, UTXO);
total += UTXO.value ;
}
}
return total;
}
public Transaction sendFunds(PublicKey _recipient, float value ) {
if(getBalance() < value) {
System.out.println("#Not Enough funds to send transaction. Transaction Discarded.");
return null;
}
ArrayList<TransactionInput> inputs = new ArrayList<TransactionInput>();
float total = 0;
for (Map.Entry<String, TransactionOutput> item: UTXOs.entrySet()) {
TransactionOutput UTXO = item.getValue();
total += UTXO.value;
inputs.add(new TransactionInput(UTXO.id));
if (total > value) break;
}
Transaction newTransaction = new Transaction(publicKey, _recipient, value, inputs);
newTransaction.generateSignature(privateKey);
for (TransactionInput input: inputs) {
UTXOs.remove(input.transactionOutputId);
}
return newTransaction;
}
}

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package tech.nevets.nevcoin.transactions;
import tech.nevets.nevcoin.NevCoin;
import tech.nevets.nevcoin.util.StringUtil;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.util.ArrayList;
public class Transaction {
public String transactionId;
public PublicKey sender;
public PublicKey recipient;
public float value;
public byte[] signature;
public ArrayList<TransactionInput> inputs = new ArrayList<TransactionInput>();
public ArrayList<TransactionOutput> outputs = new ArrayList<TransactionOutput>();
private static int sequence = 0;
public Transaction(PublicKey from, PublicKey to, float value, ArrayList<TransactionInput> inputs) {
this.sender = from;
this.recipient = to;
this.value = value;
this.inputs = inputs;
}
public boolean processTransaction() {
if (verifySignature() == false) {
System.out.println("#Transaction Signature failed to verify");
return false;
}
for (TransactionInput i : inputs) {
i.UTXO = NevCoin.UTXOs.get(i.transactionOutputId);
}
if (getInputsValue() < NevCoin.minimumTransaction) {
System.out.println("#Transaction Inputs to small: " + getInputsValue());
return false;
}
float leftOver = getInputsValue() - value;
transactionId = calculateHash();
outputs.add(new TransactionOutput( this.recipient, value, transactionId));
outputs.add(new TransactionOutput( this.sender, leftOver, transactionId));
for (TransactionOutput o : outputs) {
NevCoin.UTXOs.put(o.id, o);
}
for (TransactionInput i : inputs) {
if (i.UTXO == null) continue; //if Transaction can't be found skip it
NevCoin.UTXOs.remove(i.UTXO.id);
}
return true;
}
public float getInputsValue() {
float total = 0;
for (TransactionInput i : inputs) {
if (i.UTXO == null) continue; //if Transaction can't be found skip it
total += i.UTXO.value;
}
return total;
}
public void generateSignature(PrivateKey privateKey) {
String data = StringUtil.getStringFromKey(sender) + StringUtil.getStringFromKey(recipient) + Float.toString(value) ;
signature = StringUtil.applyECDSASig(privateKey, data);
}
public boolean verifySignature() {
String data = StringUtil.getStringFromKey(sender) + StringUtil.getStringFromKey(recipient) + Float.toString(value) ;
return StringUtil.verifyECDSASig(sender, data, signature);
}
public float getOutputsValue() {
float total = 0;
for(TransactionOutput o : outputs) {
total += o.value;
}
return total;
}
private String calculateHash() {
sequence++;
return StringUtil.applySha256(
StringUtil.getStringFromKey(sender)
+ StringUtil.getStringFromKey(recipient)
+ Float.toString(value) + sequence
);
}
}

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src/main/java/tech/nevets/nevcoin/transactions/TransactionInput.java Normal file
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package tech.nevets.nevcoin.transactions;
public class TransactionInput {
public String transactionOutputId;
public TransactionOutput UTXO;
public TransactionInput(String transactionOutputId) {
this.transactionOutputId = transactionOutputId;
}
}

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package tech.nevets.nevcoin.transactions;
import tech.nevets.nevcoin.util.StringUtil;
import java.security.PublicKey;
public class TransactionOutput {
public String id;
public PublicKey recipient;
public float value;
public String parentTransactionId;
public TransactionOutput(PublicKey recipient, float value, String parentTransactionId) {
this.recipient = recipient;
this.value = value;
this.parentTransactionId = parentTransactionId;
this.id = StringUtil.applySha256(StringUtil.getStringFromKey(recipient) + Float.toString(value)+parentTransactionId);
}
public boolean isMine(PublicKey publicKey) {
return (publicKey == recipient);
}
}

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package tech.nevets.nevcoin.util;
import com.google.gson.GsonBuilder;
import tech.nevets.nevcoin.transactions.Transaction;
import java.security.*;
import java.util.ArrayList;
import java.util.Base64;
import java.util.List;
public class StringUtil {
public static String applySha256(String input) {
try {
MessageDigest digest = MessageDigest.getInstance("SHA-256");
byte[] hash = digest.digest(input.getBytes("UTF-8"));
StringBuffer hexString = new StringBuffer();
for (int i = 0; i < hash.length; i++) {
String hex = Integer.toHexString(0xff & hash[i]);
if (hex.length() == 1) hexString.append('0');
hexString.append(hex);
}
return hexString.toString();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
public static byte[] applyECDSASig(PrivateKey privateKey, String input) {
Signature dsa;
byte[] output = new byte[0];
try {
dsa = Signature.getInstance("ECDSA", "BC");
dsa.initSign(privateKey);
byte[] strByte = input.getBytes();
dsa.update(strByte);
byte[] realSig = dsa.sign();
output = realSig;
} catch (Exception e) {
throw new RuntimeException(e);
}
return output;
}
public static boolean verifyECDSASig(PublicKey publicKey, String data, byte[] signature) {
try {
Signature ecdsaVerify = Signature.getInstance("ECDSA", "BC");
ecdsaVerify.initVerify(publicKey);
ecdsaVerify.update(data.getBytes());
return ecdsaVerify.verify(signature);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
public static String getJson(Object o) {
return new GsonBuilder().setPrettyPrinting().create().toJson(o);
}
public static String getDifficultyString(int difficulty) {
return new String(new char[difficulty]).replace('\0', '0');
}
public static String getStringFromKey(Key key) {
return Base64.getEncoder().encodeToString(key.getEncoded());
}
public static String getMerkleRoot(ArrayList<Transaction> transactions) {
int count = transactions.size();
List<String> previousTreeLayer = new ArrayList<String>();
for (Transaction transaction : transactions) {
previousTreeLayer.add(transaction.transactionId);
}
List<String> treeLayer = previousTreeLayer;
while (count > 1) {
treeLayer = new ArrayList<String>();
for(int i=1; i < previousTreeLayer.size(); i += 2) {
treeLayer.add(applySha256(previousTreeLayer.get(i - 1) + previousTreeLayer.get(i)));
}
count = treeLayer.size();
previousTreeLayer = treeLayer;
}
String merkleRoot = (treeLayer.size() == 1) ? treeLayer.get(0) : "";
return merkleRoot;
}
}