DiffieHellman Kotlin

kotlin/diffie-hellman/.exercism/metadata.json

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+{"track":"kotlin","exercise":"diffie-hellman","id":"9ef41385712144a4af4b0463a377ace9","url":"https://exercism.io/my/solutions/9ef41385712144a4af4b0463a377ace9","handle":"anthonycicc","is_requester":true,"auto_approve":false}

kotlin/diffie-hellman/.gradle/buildOutputCleanup/cache.properties

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+#Thu Mar 05 17:45:28 EST 2020
+gradle.version=6.0.1

kotlin/diffie-hellman/.idea/.gitignore

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

kotlin/diffie-hellman/.idea/compiler.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="CompilerConfiguration">
+    <bytecodeTargetLevel target="13" />
+  </component>
+</project>

kotlin/diffie-hellman/.idea/jarRepositories.xml

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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="BintrayJCenter" />
+      <option name="name" value="BintrayJCenter" />
+      <option name="url" value="https://jcenter.bintray.com/" />
+    </remote-repository>
+  </component>
+</project>

kotlin/diffie-hellman/.idea/misc.xml

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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_13" default="false" />
+</project>

kotlin/diffie-hellman/.idea/vcs.xml

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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>

kotlin/diffie-hellman/README.md

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+# Diffie-Hellman
+
+Diffie-Hellman key exchange.
+
+Alice and Bob use Diffie-Hellman key exchange to share secrets.  They
+start with prime numbers, pick private keys, generate and share public
+keys, and then generate a shared secret key.
+
+## Step 0
+
+The test program supplies prime numbers p and g.
+
+## Step 1
+
+Alice picks a private key, a, greater than 1 and less than p.  Bob does
+the same to pick a private key b.
+
+## Step 2
+
+Alice calculates a public key A.
+
+    A = g**a mod p
+
+Using the same p and g, Bob similarly calculates a public key B from his
+private key b.
+
+## Step 3
+
+Alice and Bob exchange public keys.  Alice calculates secret key s.
+
+    s = B**a mod p
+
+Bob calculates
+
+    s = A**b mod p
+
+The calculations produce the same result!  Alice and Bob now share
+secret s.
+
+## Setup
+
+Go through the setup instructions for Kotlin to install the necessary
+dependencies:
+
+[https://exercism.io/tracks/kotlin/installation](https://exercism.io/tracks/kotlin/installation)
+
+## Making the test suite pass
+
+Execute the tests with:
+
+```bash
+$ gradlew test
+```
+
+> Use `gradlew.bat` if you're on Windows
+
+In the test suites all tests but the first have been skipped.
+
+Once you get a test passing, you can enable the next one by removing the
+`@Ignore` annotation.
+
+## Source
+
+Wikipedia, 1024 bit key from www.cryptopp.com/wiki. [http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange](http://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange)
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have
+completed the exercise.

kotlin/diffie-hellman/build.gradle.kts

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+import org.gradle.api.tasks.testing.logging.TestExceptionFormat
+
+plugins {
+    kotlin("jvm") version "1.3.60"
+}
+
+repositories {
+    jcenter()
+}
+
+dependencies {
+    compile(kotlin("stdlib"))
+    
+    testImplementation("junit:junit:4.12")
+    testImplementation(kotlin("test-junit"))
+}
+
+tasks.withType<Test> {
+    testLogging {
+        exceptionFormat = TestExceptionFormat.FULL
+        events("passed", "failed", "skipped")
+    }
+}

kotlin/diffie-hellman/gradle/wrapper/gradle-wrapper.properties

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.0.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

kotlin/diffie-hellman/gradlew

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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 "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$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`="\"$arg\""
+        fi
+        i=$((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"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"

kotlin/diffie-hellman/gradlew.bat

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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 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 init
+
+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 init
+
+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
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+: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 %CMD_LINE_ARGS%
+
+: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

kotlin/diffie-hellman/src/main/kotlin/DiffieHellman.kt

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+import java.math.BigInteger
+import java.util.*
+
+object DiffieHellman {
+
+    fun privateKey(prime: BigInteger): BigInteger {
+        var returnVal: BigInteger
+        val random = Random()
+        do {
+            returnVal = BigInteger.probablePrime(random.nextInt(prime.bitLength()).coerceAtLeast(2), random)
+        } while (returnVal >= prime && returnVal != 0.toBigInteger())
+        return returnVal
+    }
+
+    fun publicKey(p: BigInteger, g: BigInteger, privKey: BigInteger): BigInteger {
+        return g.modPow(privKey, p)
+    }
+
+    fun secret(prime: BigInteger, publicKey: BigInteger, privateKey: BigInteger): BigInteger {
+        return publicKey.modPow(privateKey, prime)
+    }
+}

kotlin/diffie-hellman/src/test/kotlin/DiffieHellmanTest.kt

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+import org.junit.Test
+import java.math.BigInteger
+import kotlin.test.assertEquals
+import kotlin.test.assertNotEquals
+import kotlin.test.assertTrue
+
+class DiffieHellmanTest {
+
+    @Test
+    fun `private key is in range from 1 to prime`() {
+        val prime = 23.toBigInteger()
+        (0..9).map { DiffieHellman.privateKey(prime) }.forEach {
+            assertTrue(it >= BigInteger.ONE)
+            assertTrue(it < prime)
+        }
+    }
+
+    /**
+     * Due to the nature of randomness, there is always a chance that this test fails.
+     * Be sure to check the actual generated values.
+     */
+    @Test
+    fun `private key is random`() {
+        val prime = 7919.toBigInteger()
+        val privateKeyA = DiffieHellman.privateKey(prime)
+        val privateKeyB = DiffieHellman.privateKey(prime)
+
+        assertNotEquals(privateKeyA, privateKeyB)
+    }
+
+    @Test
+    fun `calculate public key using private key`() {
+        val primeA = 23.toBigInteger()
+        val primeB = 5.toBigInteger()
+        val privateKey = 6.toBigInteger()
+        val expected = 8.toBigInteger()
+
+        assertEquals(expected, DiffieHellman.publicKey(primeA, primeB, privateKey))
+    }
+
+
+    @Test
+    fun `calculate secret using other party's public key`() {
+        val prime = 23.toBigInteger()
+        val publicKey = 19.toBigInteger()
+        val privateKey = 6.toBigInteger()
+        val expected = 2.toBigInteger()
+
+        assertEquals(expected, DiffieHellman.secret(prime, publicKey, privateKey))
+    }
+
+
+    @Test
+    fun `key exchange`() {
+        val primeA = 23.toBigInteger()
+        val primeB = 5.toBigInteger()
+
+        val alicePrivateKey = DiffieHellman.privateKey(primeA)
+        val bobPrivateKey = DiffieHellman.privateKey(primeB)
+
+        val alicePublicKey = DiffieHellman.publicKey(primeA, primeB, alicePrivateKey)
+        val bobPublicKey = DiffieHellman.publicKey(primeA, primeB, bobPrivateKey)
+
+        val secretA = DiffieHellman.secret(primeA, bobPublicKey, alicePrivateKey)
+        val secretB = DiffieHellman.secret(primeA, alicePublicKey, bobPrivateKey)
+
+        assertEquals(secretA, secretB)
+    }
+
+}