Add android implementation

native_crypto_android/.gitignore

@@ -0,0 +1,29 @@
+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+# Libraries should not include pubspec.lock, per https://dart.dev/guides/libraries/private-files#pubspeclock.
+/pubspec.lock
+**/doc/api/
+.dart_tool/
+.packages
+build/

native_crypto_android/.metadata

@@ -0,0 +1,10 @@
+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: 77d935af4db863f6abd0b9c31c7e6df2a13de57b
+  channel: stable
+
+project_type: plugin

native_crypto_android/CHANGELOG.md

@@ -0,0 +1 @@
+Check [`native_crypto`](../native_crypto/CHANGELOG.md) plugin's changelog.

native_crypto_android/LICENSE

@@ -0,0 +1,23 @@
+NativeCrypto - Android Implementation
+
+MIT License
+
+Copyright (c) 2019 - 2022 Hugo Pointcheval
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

native_crypto_android/README.md

@@ -0,0 +1,15 @@
+# native_crypto_android
+
+A new flutter plugin project.
+
+## Getting Started
+
+This project is a starting point for a Flutter
+[plug-in package](https://flutter.dev/developing-packages/),
+a specialized package that includes platform-specific implementation code for
+Android and/or iOS.
+
+For help getting started with Flutter, view our
+[online documentation](https://flutter.dev/docs), which offers tutorials,
+samples, guidance on mobile development, and a full API reference.
+

native_crypto_android/android/.gitignore

@@ -0,0 +1,8 @@
+*.iml
+.gradle
+/local.properties
+/.idea/workspace.xml
+/.idea/libraries
+.DS_Store
+/build
+/captures

native_crypto_android/android/build.gradle

@@ -0,0 +1,50 @@
+group 'fr.pointcheval.native_crypto_android'
+version '1.0-SNAPSHOT'
+
+buildscript {
+    ext.kotlin_version = '1.3.50'
+    repositories {
+        google()
+        mavenCentral()
+    }
+
+    dependencies {
+        classpath 'com.android.tools.build:gradle:4.1.0'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+rootProject.allprojects {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
+
+android {
+    compileSdkVersion 30
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = '1.8'
+    }
+
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+    }
+
+    defaultConfig {
+        minSdkVersion 26
+    }
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+}

native_crypto_android/android/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

native_crypto_android/android/gradlew

@@ -0,0 +1,185 @@
+#!/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=`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 "$JAVACMD" "$@"

native_crypto_android/android/gradlew.bat

@@ -0,0 +1,89 @@
+@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

native_crypto_android/android/settings.gradle

@@ -0,0 +1 @@
+rootProject.name = 'native_crypto_android'

native_crypto_android/android/src/main/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+  package="fr.pointcheval.native_crypto_android">
+</manifest>

native_crypto_android/android/src/main/kotlin/fr/pointcheval/native_crypto_android/Cipher.kt

@@ -0,0 +1,6 @@
+package fr.pointcheval.native_crypto_android
+
+abstract class Cipher {
+    abstract fun encrypt(data: ByteArray, key: ByteArray) : ByteArray?;
+    abstract fun decrypt(data: ByteArray, key: ByteArray) : ByteArray?;
+}

native_crypto_android/android/src/main/kotlin/fr/pointcheval/native_crypto_android/Hash.kt

@@ -0,0 +1,25 @@
+package fr.pointcheval.native_crypto_android
+
+import java.security.MessageDigest
+
+object Hash {
+    fun digest(data: ByteArray?, algorithm: HashAlgorithm): ByteArray {
+        val func : String = when (algorithm) {
+            HashAlgorithm.SHA256 -> "SHA-256"
+            HashAlgorithm.SHA384 -> "SHA-384"
+            HashAlgorithm.SHA512 -> "SHA-512"
+        }
+        val md = MessageDigest.getInstance(func)
+        return md.digest(data)
+    }
+
+    fun digest(data: ByteArray?, algorithm: String): ByteArray {
+        val func : HashAlgorithm = when (algorithm) {
+            "sha256" -> HashAlgorithm.SHA256
+            "sha384" -> HashAlgorithm.SHA384
+            "sha512" -> HashAlgorithm.SHA512
+            else -> HashAlgorithm.SHA256
+        }
+        return digest(data, func)
+    }
+}

native_crypto_android/android/src/main/kotlin/fr/pointcheval/native_crypto_android/HashAlgorithm.kt

@@ -0,0 +1,15 @@
+package fr.pointcheval.native_crypto_android
+
+enum class HashAlgorithm(val length : Int) {
+    SHA256(256),
+    SHA384(384),
+    SHA512(512);
+
+    fun hmac(): String {
+        return when (this) {
+            HashAlgorithm.SHA256 -> "HmacSHA256"
+            HashAlgorithm.SHA384 -> "HmacSHA384"
+            HashAlgorithm.SHA512 -> "HmacSHA512"
+        }
+    }
+}

native_crypto_android/android/src/main/kotlin/fr/pointcheval/native_crypto_android/Key.kt

@@ -0,0 +1,24 @@
+package fr.pointcheval.native_crypto_android
+
+import java.security.SecureRandom
+import javax.crypto.SecretKeyFactory
+import javax.crypto.spec.PBEKeySpec
+
+object Key {
+     fun fromSecureRandom(bitsCount: Int) : ByteArray {
+         val bytes = ByteArray(bitsCount / 8)
+         SecureRandom.getInstanceStrong().nextBytes(bytes)
+         return bytes
+     }
+
+    fun fromPBKDF2(password: String, salt: String, keyBytesCount: Int, iterations: Int, algorithm: String): ByteArray {
+        val availableHashAlgorithm: Map<String, String> = mapOf(
+            "sha256" to "PBKDF2WithHmacSHA256",
+            "sha384" to "PBKDF2withHmacSHA384",
+            "sha512" to "PBKDF2withHmacSHA512"
+        )
+        val spec = PBEKeySpec(password.toCharArray(), salt.toByteArray(), iterations, keyBytesCount * 8)
+        val skf: SecretKeyFactory = SecretKeyFactory.getInstance(availableHashAlgorithm[algorithm])
+        return skf.generateSecret(spec).encoded
+    }
+}

native_crypto_android/android/src/main/kotlin/fr/pointcheval/native_crypto_android/NativeCryptoAndroidPlugin.kt

@@ -0,0 +1,77 @@
+package fr.pointcheval.native_crypto_android
+
+import androidx.annotation.NonNull
+import fr.pointcheval.native_crypto_android.ciphers.AESCipher
+
+import io.flutter.embedding.engine.plugins.FlutterPlugin
+import io.flutter.plugin.common.MethodCall
+import io.flutter.plugin.common.MethodChannel
+import io.flutter.plugin.common.MethodChannel.MethodCallHandler
+import io.flutter.plugin.common.MethodChannel.Result
+
+/** NativeCryptoAndroidPlugin */
+class NativeCryptoAndroidPlugin: FlutterPlugin, MethodCallHandler {
+  /// The MethodChannel that will the communication between Flutter and native Android
+  ///
+  /// This local reference serves to register the plugin with the Flutter Engine and unregister it
+  /// when the Flutter Engine is detached from the Activity
+  private lateinit var channel : MethodChannel
+
+  override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
+    channel = MethodChannel(flutterPluginBinding.binaryMessenger, "plugins.hugop.cl/native_crypto")
+    channel.setMethodCallHandler(this)
+  }
+
+  override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: Result) {
+    when (call.method) {
+      "digest" -> {
+        val data : ByteArray? = call.argument<ByteArray>("data")
+        val algorithm : String? = call.argument<String>("algorithm")
+        // TODO(hpcl): check if algorithm is null
+        // TODO(hpcl): check if digest is null
+        result.success(Hash.digest(data, algorithm!!))
+      }
+      "generateSecretKey" -> {
+        val bitsCount : Int? = call.argument<Int>("bitsCount")
+        // TODO(hpcl): check null
+        result.success(Key.fromSecureRandom(bitsCount!!))
+      }
+      "generateKeyPair" -> {
+        result.notImplemented()
+      }
+      "pbkdf2" -> {
+        val password : String? = call.argument<String>("password")
+        val salt : String? = call.argument<String>("salt")
+        val keyBytesCount : Int? = call.argument<Int>("keyBytesCount")
+        val iterations : Int? = call.argument<Int>("iterations")
+        val algorithm : String? = call.argument<String>("algorithm")
+        // TODO(hpcl): check null
+        result.success(Key.fromPBKDF2(password!!, salt!!, keyBytesCount!!, iterations!!, algorithm!!))
+      }
+      "encrypt" -> {
+        val data : ByteArray? = call.argument<ByteArray>("data")
+        val key : ByteArray? = call.argument<ByteArray>("key")
+        val algorithm : String? = call.argument<String>("algorithm")
+        // TODO(hpcl): check null
+        // TODO(hcpl): check algorithm
+        result.success(AESCipher().encrypt(data!!, key!!))
+      }
+      "decrypt" ->  {
+        val data : ByteArray? = call.argument<ByteArray>("data")
+        val key : ByteArray? = call.argument<ByteArray>("key")
+        val algorithm : String? = call.argument<String>("algorithm")
+        // TODO(hpcl): check null
+        // TODO(hcpl): check algorithm
+        result.success(AESCipher().decrypt(data!!, key!!))
+      }
+      "generateSharedSecretKey" -> {
+        result.notImplemented()
+      }
+      else -> result.notImplemented()
+    }
+  }
+
+  override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
+    channel.setMethodCallHandler(null)
+  }
+}

native_crypto_android/android/src/main/kotlin/fr/pointcheval/native_crypto_android/ciphers/AESCipher.kt

@@ -0,0 +1,31 @@
+package fr.pointcheval.native_crypto_android.ciphers
+
+import fr.pointcheval.native_crypto_android.Cipher
+import javax.crypto.SecretKey
+import javax.crypto.spec.GCMParameterSpec
+import javax.crypto.spec.SecretKeySpec
+
+class AESCipher : Cipher() {
+    override fun encrypt(data: ByteArray, key: ByteArray): ByteArray {
+        val sk: SecretKey = SecretKeySpec(key, "AES")
+        val cipher = javax.crypto.Cipher.getInstance("AES/GCM/NoPadding")
+        cipher.init(javax.crypto.Cipher.ENCRYPT_MODE, sk)
+        // javax.crypto representation = [CIPHERTEXT(n-28) || TAG(16)]
+        val bytes = cipher.doFinal(data)
+        val iv = cipher.iv.copyOf()                                                 // 12 bytes nonce
+        // native.crypto representation = [NONCE(12) || CIPHERTEXT(n-28) || TAG(16)]
+        return iv.plus(bytes)
+    }
+
+    override fun decrypt(data: ByteArray, key: ByteArray): ByteArray? {
+        val sk: SecretKey = SecretKeySpec(key, "AES")
+        // native.crypto representation = [NONCE(12) || CIPHERTEXT(n-28) || TAG(16)]
+        val iv = data.sliceArray(IntRange(0,11))                              // 12 bytes nonce
+        // javax.crypto representation = [CIPHERTEXT(n-28) || TAG(16)]
+        val payload = data.sliceArray(IntRange(12, data.size - 1))
+        val spec = GCMParameterSpec(16 * 8, iv)
+        val cipher = javax.crypto.Cipher.getInstance("AES/GCM/NoPadding")
+        cipher.init(javax.crypto.Cipher.DECRYPT_MODE, sk, spec)
+        return cipher.doFinal(payload)
+    }
+}

native_crypto_android/example/.gitignore

@@ -0,0 +1,46 @@
+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins
+.flutter-plugins-dependencies
+.packages
+.pub-cache/
+.pub/
+/build/
+
+# Web related
+lib/generated_plugin_registrant.dart
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release

native_crypto_android/example/.metadata

@@ -0,0 +1,10 @@
+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: 77d935af4db863f6abd0b9c31c7e6df2a13de57b
+  channel: stable
+
+project_type: app

native_crypto_android/example/README.md

@@ -0,0 +1,16 @@
+# native_crypto_android_example
+
+Demonstrates how to use the native_crypto_android plugin.
+
+## Getting Started
+
+This project is a starting point for a Flutter application.
+
+A few resources to get you started if this is your first Flutter project:
+
+- [Lab: Write your first Flutter app](https://flutter.dev/docs/get-started/codelab)
+- [Cookbook: Useful Flutter samples](https://flutter.dev/docs/cookbook)
+
+For help getting started with Flutter, view our
+[online documentation](https://flutter.dev/docs), which offers tutorials,
+samples, guidance on mobile development, and a full API reference.

native_crypto_android/example/analysis_options.yaml

@@ -0,0 +1,29 @@
+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at
+  # https://dart-lang.github.io/linter/lints/index.html.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

native_crypto_android/example/android/.gitignore

@@ -0,0 +1,13 @@
+gradle-wrapper.jar
+/.gradle
+/captures/
+/gradlew
+/gradlew.bat
+/local.properties
+GeneratedPluginRegistrant.java
+
+# Remember to never publicly share your keystore.
+# See https://flutter.dev/docs/deployment/android#reference-the-keystore-from-the-app
+key.properties
+**/*.keystore
+**/*.jks

native_crypto_android/example/android/app/build.gradle

@@ -0,0 +1,68 @@
+def localProperties = new Properties()
+def localPropertiesFile = rootProject.file('local.properties')
+if (localPropertiesFile.exists()) {
+    localPropertiesFile.withReader('UTF-8') { reader ->
+        localProperties.load(reader)
+    }
+}
+
+def flutterRoot = localProperties.getProperty('flutter.sdk')
+if (flutterRoot == null) {
+    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
+}
+
+def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
+if (flutterVersionCode == null) {
+    flutterVersionCode = '1'
+}
+
+def flutterVersionName = localProperties.getProperty('flutter.versionName')
+if (flutterVersionName == null) {
+    flutterVersionName = '1.0'
+}
+
+apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android'
+apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
+
+android {
+    compileSdkVersion flutter.compileSdkVersion
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = '1.8'
+    }
+
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+    }
+
+    defaultConfig {
+        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
+        applicationId "fr.pointcheval.native_crypto_android_example"
+        minSdkVersion 26
+        targetSdkVersion flutter.targetSdkVersion
+        versionCode flutterVersionCode.toInteger()
+        versionName flutterVersionName
+    }
+
+    buildTypes {
+        release {
+            // TODO: Add your own signing config for the release build.
+            // Signing with the debug keys for now, so `flutter run --release` works.
+            signingConfig signingConfigs.debug
+        }
+    }
+}
+
+flutter {
+    source '../..'
+}
+
+dependencies {
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+}

native_crypto_android/example/android/app/src/debug/AndroidManifest.xml

@@ -0,0 +1,7 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="fr.pointcheval.native_crypto_android_example">
+    <!-- Flutter needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

native_crypto_android/example/android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,34 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="fr.pointcheval.native_crypto_android_example">
+   <application
+        android:label="native_crypto_android_example"
+        android:name="${applicationName}"
+        android:icon="@mipmap/ic_launcher">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:launchMode="singleTop"
+            android:theme="@style/LaunchTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize">
+            <!-- Specifies an Android theme to apply to this Activity as soon as
+                 the Android process has started. This theme is visible to the user
+                 while the Flutter UI initializes. After that, this theme continues
+                 to determine the Window background behind the Flutter UI. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.NormalTheme"
+              android:resource="@style/NormalTheme"
+              />
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
+    </application>
+</manifest>

native_crypto_android/example/android/app/src/main/kotlin/fr/pointcheval/native_crypto_android_example/MainActivity.kt

@@ -0,0 +1,6 @@
+package fr.pointcheval.native_crypto_android_example
+
+import io.flutter.embedding.android.FlutterActivity
+
+class MainActivity: FlutterActivity() {
+}

native_crypto_android/example/android/app/src/main/res/drawable-v21/launch_background.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="?android:colorBackground" />
+
+    <!-- You can insert your own image assets here -->
+    <!-- <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item> -->
+</layer-list>

native_crypto_android/example/android/app/src/main/res/drawable/launch_background.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@android:color/white" />
+
+    <!-- You can insert your own image assets here -->
+    <!-- <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item> -->
+</layer-list>

native_crypto_android/example/android/app/src/main/res/values-night/styles.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting when the OS's Dark Mode setting is on -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <!-- Show a splash screen on the activity. Automatically removed when
+             Flutter draws its first frame -->
+        <item name="android:windowBackground">@drawable/launch_background</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <item name="android:windowBackground">?android:colorBackground</item>
+    </style>
+</resources>

native_crypto_android/example/android/app/src/main/res/values/styles.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting when the OS's Dark Mode setting is off -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Light.NoTitleBar">
+        <!-- Show a splash screen on the activity. Automatically removed when
+             Flutter draws its first frame -->
+        <item name="android:windowBackground">@drawable/launch_background</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Light.NoTitleBar">
+        <item name="android:windowBackground">?android:colorBackground</item>
+    </style>
+</resources>

native_crypto_android/example/android/app/src/profile/AndroidManifest.xml

@@ -0,0 +1,7 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="fr.pointcheval.native_crypto_android_example">
+    <!-- Flutter needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

native_crypto_android/example/android/build.gradle

@@ -0,0 +1,31 @@
+buildscript {
+    ext.kotlin_version = '1.3.50'
+    repositories {
+        google()
+        mavenCentral()
+    }
+
+    dependencies {
+        classpath 'com.android.tools.build:gradle:4.1.0'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+rootProject.buildDir = '../build'
+subprojects {
+    project.buildDir = "${rootProject.buildDir}/${project.name}"
+}
+subprojects {
+    project.evaluationDependsOn(':app')
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}

native_crypto_android/example/android/gradle.properties

@@ -0,0 +1,3 @@
+org.gradle.jvmargs=-Xmx1536M
+android.useAndroidX=true
+android.enableJetifier=true

native_crypto_android/example/android/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Fri Jun 23 08:50:38 CEST 2017
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip

native_crypto_android/example/android/settings.gradle

@@ -0,0 +1,11 @@
+include ':app'
+
+def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
+def properties = new Properties()
+
+assert localPropertiesFile.exists()
+localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
+
+def flutterSdkPath = properties.getProperty("flutter.sdk")
+assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"

native_crypto_android/example/lib/main.dart

@@ -0,0 +1,75 @@
+import 'dart:typed_data';
+
+import 'package:flutter/material.dart';
+import 'dart:async';
+
+import 'package:flutter/services.dart';
+import 'package:native_crypto_platform_interface/native_crypto_platform_interface.dart';
+
+void main() {
+  runApp(const MyApp());
+}
+
+class MyApp extends StatefulWidget {
+  const MyApp({Key? key}) : super(key: key);
+
+  @override
+  State<MyApp> createState() => _MyAppState();
+}
+
+class _MyAppState extends State<MyApp> {
+  String _platformVersion = 'Unknown';
+
+  @override
+  void initState() {
+    super.initState();
+    initPlatformState();
+  }
+
+  // Platform messages are asynchronous, so we initialize in an async method.
+  Future<void> initPlatformState() async {
+    NativeCryptoPlatform _nativeCryptoPlatform = NativeCryptoPlatform.instance;
+    String platformVersion;
+    // Platform messages may fail, so we use a try/catch PlatformException.
+    // We also handle the message potentially returning null.
+    Uint8List? sk = await _nativeCryptoPlatform.generateSecretKey(256);
+    print(sk ?? 'null');
+
+    Uint8List? ciphertext = await _nativeCryptoPlatform.encrypt(
+        Uint8List.fromList("abc".codeUnits), sk!, "aes");
+    print(ciphertext ?? 'null');
+
+    Uint8List? plaintext =
+        await _nativeCryptoPlatform.decrypt(ciphertext!, sk, "aes");
+    print(plaintext ?? 'null');
+
+    try {
+      platformVersion = 'Unknown platform version';
+    } on PlatformException {
+      platformVersion = 'Failed to get platform version.';
+    }
+
+    // If the widget was removed from the tree while the asynchronous platform
+    // message was in flight, we want to discard the reply rather than calling
+    // setState to update our non-existent appearance.
+    if (!mounted) return;
+
+    setState(() {
+      _platformVersion = platformVersion;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: Scaffold(
+        appBar: AppBar(
+          title: const Text('Plugin example app'),
+        ),
+        body: Center(
+          child: Text('Running on: $_platformVersion\n'),
+        ),
+      ),
+    );
+  }
+}

native_crypto_android/example/pubspec.lock

@@ -0,0 +1,182 @@
+# Generated by pub
+# See https://dart.dev/tools/pub/glossary#lockfile
+packages:
+  async:
+    dependency: transitive
+    description:
+      name: async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.8.2"
+  boolean_selector:
+    dependency: transitive
+    description:
+      name: boolean_selector
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.0"
+  characters:
+    dependency: transitive
+    description:
+      name: characters
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.2.0"
+  charcode:
+    dependency: transitive
+    description:
+      name: charcode
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.3.1"
+  clock:
+    dependency: transitive
+    description:
+      name: clock
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0"
+  collection:
+    dependency: transitive
+    description:
+      name: collection
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.15.0"
+  cupertino_icons:
+    dependency: "direct main"
+    description:
+      name: cupertino_icons
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.4"
+  fake_async:
+    dependency: transitive
+    description:
+      name: fake_async
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.2.0"
+  flutter:
+    dependency: "direct main"
+    description: flutter
+    source: sdk
+    version: "0.0.0"
+  flutter_lints:
+    dependency: "direct dev"
+    description:
+      name: flutter_lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.4"
+  flutter_test:
+    dependency: "direct dev"
+    description: flutter
+    source: sdk
+    version: "0.0.0"
+  lints:
+    dependency: transitive
+    description:
+      name: lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
+  matcher:
+    dependency: transitive
+    description:
+      name: matcher
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.12.11"
+  meta:
+    dependency: transitive
+    description:
+      name: meta
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.7.0"
+  native_crypto_android:
+    dependency: "direct main"
+    description:
+      path: ".."
+      relative: true
+    source: path
+    version: "0.1.0"
+  native_crypto_platform_interface:
+    dependency: "direct main"
+    description:
+      path: "../../native_crypto_platform_interface"
+      relative: true
+    source: path
+    version: "0.0.7"
+  path:
+    dependency: transitive
+    description:
+      name: path
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.8.0"
+  sky_engine:
+    dependency: transitive
+    description: flutter
+    source: sdk
+    version: "0.0.99"
+  source_span:
+    dependency: transitive
+    description:
+      name: source_span
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.8.1"
+  stack_trace:
+    dependency: transitive
+    description:
+      name: stack_trace
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.10.0"
+  stream_channel:
+    dependency: transitive
+    description:
+      name: stream_channel
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.0"
+  string_scanner:
+    dependency: transitive
+    description:
+      name: string_scanner
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.1.0"
+  term_glyph:
+    dependency: transitive
+    description:
+      name: term_glyph
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.2.0"
+  test_api:
+    dependency: transitive
+    description:
+      name: test_api
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "0.4.3"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.3.0"
+  vector_math:
+    dependency: transitive
+    description:
+      name: vector_math
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.1.1"
+sdks:
+  dart: ">=2.15.1 <3.0.0"
+  flutter: ">=2.5.0"

native_crypto_android/example/pubspec.yaml

@@ -0,0 +1,87 @@
+name: native_crypto_android_example
+description: Demonstrates how to use the native_crypto_android plugin.
+
+# The following line prevents the package from being accidentally published to
+# pub.dev using `flutter pub publish`. This is preferred for private packages.
+publish_to: 'none' # Remove this line if you wish to publish to pub.dev
+
+environment:
+  sdk: ">=2.15.1 <3.0.0"
+
+# Dependencies specify other packages that your package needs in order to work.
+# To automatically upgrade your package dependencies to the latest versions
+# consider running `flutter pub upgrade --major-versions`. Alternatively,
+# dependencies can be manually updated by changing the version numbers below to
+# the latest version available on pub.dev. To see which dependencies have newer
+# versions available, run `flutter pub outdated`.
+dependencies:
+  flutter:
+    sdk: flutter
+
+  native_crypto_android:
+    # When depending on this package from a real application you should use:
+    #   native_crypto_android: ^x.y.z
+    # See https://dart.dev/tools/pub/dependencies#version-constraints
+    # The example app is bundled with the plugin so we use a path dependency on
+    # the parent directory to use the current plugin's version.
+    path: ../
+
+  native_crypto_platform_interface:
+    path: ../../native_crypto_platform_interface
+
+  # The following adds the Cupertino Icons font to your application.
+  # Use with the CupertinoIcons class for iOS style icons.
+  cupertino_icons: ^1.0.2
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+
+  # The "flutter_lints" package below contains a set of recommended lints to
+  # encourage good coding practices. The lint set provided by the package is
+  # activated in the `analysis_options.yaml` file located at the root of your
+  # package. See that file for information about deactivating specific lint
+  # rules and activating additional ones.
+  flutter_lints: ^1.0.0
+
+# For information on the generic Dart part of this file, see the
+# following page: https://dart.dev/tools/pub/pubspec
+
+# The following section is specific to Flutter.
+flutter:
+
+  # The following line ensures that the Material Icons font is
+  # included with your application, so that you can use the icons in
+  # the material Icons class.
+  uses-material-design: true
+
+  # To add assets to your application, add an assets section, like this:
+  # assets:
+  #   - images/a_dot_burr.jpeg
+  #   - images/a_dot_ham.jpeg
+
+  # An image asset can refer to one or more resolution-specific "variants", see
+  # https://flutter.dev/assets-and-images/#resolution-aware.
+
+  # For details regarding adding assets from package dependencies, see
+  # https://flutter.dev/assets-and-images/#from-packages
+
+  # To add custom fonts to your application, add a fonts section here,
+  # in this "flutter" section. Each entry in this list should have a
+  # "family" key with the font family name, and a "fonts" key with a
+  # list giving the asset and other descriptors for the font. For
+  # example:
+  # fonts:
+  #   - family: Schyler
+  #     fonts:
+  #       - asset: fonts/Schyler-Regular.ttf
+  #       - asset: fonts/Schyler-Italic.ttf
+  #         style: italic
+  #   - family: Trajan Pro
+  #     fonts:
+  #       - asset: fonts/TrajanPro.ttf
+  #       - asset: fonts/TrajanPro_Bold.ttf
+  #         weight: 700
+  #
+  # For details regarding fonts from package dependencies,
+  # see https://flutter.dev/custom-fonts/#from-packages

native_crypto_android/example/test/widget_test.dart

@@ -0,0 +1,27 @@
+// This is a basic Flutter widget test.
+//
+// To perform an interaction with a widget in your test, use the WidgetTester
+// utility that Flutter provides. For example, you can send tap and scroll
+// gestures. You can also use WidgetTester to find child widgets in the widget
+// tree, read text, and verify that the values of widget properties are correct.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:native_crypto_android_example/main.dart';
+
+void main() {
+  testWidgets('Verify Platform version', (WidgetTester tester) async {
+    // Build our app and trigger a frame.
+    await tester.pumpWidget(const MyApp());
+
+    // Verify that platform version is retrieved.
+    expect(
+      find.byWidgetPredicate(
+        (Widget widget) => widget is Text &&
+                           widget.data!.startsWith('Running on:'),
+      ),
+      findsOneWidget,
+    );
+  });
+}

native_crypto_android/pubspec.yaml

@@ -0,0 +1,23 @@
+name: native_crypto_android
+description: Android implementation of NativeCrypto
+version: 0.1.0
+
+environment:
+  sdk: ">=2.15.1 <3.0.0"
+  flutter: ">=2.5.0"
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+
+flutter:
+  plugin:
+    implements: native_crypto
+    platforms:
+      android:
+        package: fr.pointcheval.native_crypto_android
+        pluginClass: NativeCryptoAndroidPlugin