diff --git a/.github/workflows/builder.yaml b/.github/workflows/builder.yaml
new file mode 100644
index 0000000..1b94794
--- /dev/null
+++ b/.github/workflows/builder.yaml
@@ -0,0 +1,49 @@
+---
+name: "build-docker-image"
+
+on:
+  pull_request:
+
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        platform: [ linux/amd64, linux/arm64 ]
+
+    steps:
+      - name: "Checkout the repository"
+        uses: actions/checkout@v4
+
+      - name: "Extract metadata for the Docker image"
+        if: github.event_name == 'push' && github.ref_type == 'tag' # Only extract metadata if we push a tag
+        id: metadata_extraction
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+
+      - name: "Login to GitHub Container Registry"
+        if: github.event_name == 'push' && github.ref_type == 'tag' # Only login if we push a tag
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: "Set up Docker Buildx"
+        uses: docker/setup-buildx-action@v3
+
+      - name: "Build and eventually push container image"
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./Dockerfile
+          platforms: ${{ matrix.platform }}
+          tags: ${{ steps.metadata_extraction.outputs.tags }}
+          labels: ${{ steps.metadata_extraction.outputs.labels }}
+          push: ${{ github.event_name == 'push' && github.ref_type == 'tag' }} # Only push built image if we push a tag
\ No newline at end of file
diff --git a/.github/workflows/commit-checks.yaml b/.github/workflows/commit-checks.yaml
new file mode 100644
index 0000000..b3a0cd3
--- /dev/null
+++ b/.github/workflows/commit-checks.yaml
@@ -0,0 +1,18 @@
+---
+name: "commits-checks"
+
+on:
+  pull_request:
+
+jobs:
+  commits-checks:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: "Check out the repository"
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0 # Fetch all history for all tags and branches
+
+      - name: "Check commit messages"
+        uses: docker://aevea/commitsar
diff --git a/.github/workflows/release-please.yaml b/.github/workflows/release-please.yaml
new file mode 100644
index 0000000..5ed06d7
--- /dev/null
+++ b/.github/workflows/release-please.yaml
@@ -0,0 +1,19 @@
+---
+name: "release-please"
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  release-please:
+    runs-on: ubuntu-latest
+    outputs:
+      releases_created: ${{ steps.release-please.outputs.releases_created }}
+    steps:
+      - uses: google-github-actions/release-please-action@v4
+        id: release-please
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          release-type: maven
diff --git a/.gitignore b/.gitignore
index 030930d..a07ca35 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@
 .idea/jarRepositories.xml
 .idea/modules.xml
 .idea/workspace.xml
+.idea/uiDesigner.xml
 *.iws
 *.iml
 *.ipr
diff --git a/.idea/codeStyles/Project.xml b/.idea/codeStyles/Project.xml
index 155ea54..5466105 100644
--- a/.idea/codeStyles/Project.xml
+++ b/.idea/codeStyles/Project.xml
@@ -140,6 +140,10 @@
       </indentOptions>
     </codeStyleSettings>
     <codeStyleSettings language="JAVA">
+      <option name="LINE_COMMENT_AT_FIRST_COLUMN" value="false" />
+      <option name="BLOCK_COMMENT_AT_FIRST_COLUMN" value="false" />
+      <option name="LINE_COMMENT_ADD_SPACE" value="true" />
+      <option name="LINE_COMMENT_ADD_SPACE_ON_REFORMAT" value="true" />
       <option name="KEEP_CONTROL_STATEMENT_IN_ONE_LINE" value="false" />
       <option name="KEEP_BLANK_LINES_IN_CODE" value="1" />
       <option name="BLANK_LINES_AFTER_CLASS_HEADER" value="1" />
diff --git a/.release-please-manifest.json b/.release-please-manifest.json
new file mode 100644
index 0000000..466df71
--- /dev/null
+++ b/.release-please-manifest.json
@@ -0,0 +1,3 @@
+{
+  ".": "0.1.0"
+}
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..0662553
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,12 @@
+FROM maven:3.9-eclipse-temurin-21 AS build
+WORKDIR /project
+COPY . .
+RUN if [ -d "target" ]; then rm -rf target; fi; \
+    ./mvnw dependency:go-offline clean compile package; \
+    rm -rf target/original-*.jar # Remove original jar otherwise it will be copied to the final image.
+
+FROM eclipse-temurin:21-jre
+COPY --from=build /project/target/*.jar /app/shadow.jar
+WORKDIR /data
+ENTRYPOINT ["java", "-jar", "/app/shadow.jar"]
+CMD ["--help"]
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..2bf46a3
--- /dev/null
+++ b/README.md
@@ -0,0 +1,6 @@
+# DAI-2024-PW1
+
+This repository contains the code for our first practical work in the DAI course of HEIG-VD during 2024.
+
+// TODO Add comment saying that files are different because hash is different
+// TODO Same as before but to say message before and after has the same hash
diff --git a/dependency-reduced-pom.xml b/dependency-reduced-pom.xml
index e26d8bb..c66de88 100644
--- a/dependency-reduced-pom.xml
+++ b/dependency-reduced-pom.xml
@@ -2,8 +2,8 @@
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <groupId>ch.heigvd.dai</groupId>
-  <artifactId>DAI-2425-PW1</artifactId>
-  <version>1.0-SNAPSHOT</version>
+  <artifactId>shadow</artifactId>
+  <version>0.0.1</version>
   <build>
     <plugins>
       <plugin>
diff --git a/pom.xml b/pom.xml
index 12dd641..9b6cd02 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,8 +3,8 @@
   <modelVersion>4.0.0</modelVersion>
 
   <groupId>ch.heigvd.dai</groupId>
-  <artifactId>DAI-2425-PW1</artifactId>
-  <version>1.0-SNAPSHOT</version>
+  <artifactId>shadow</artifactId>
+  <version>0.0.1</version>
 
   <properties>
     <maven.compiler.source>21</maven.compiler.source>
diff --git a/release-please-manifest.json b/release-please-manifest.json
new file mode 100644
index 0000000..19f865e
--- /dev/null
+++ b/release-please-manifest.json
@@ -0,0 +1,26 @@
+{
+  "packages": {
+    ".": {
+      "release-type": "maven"
+    }
+  },
+  "changelog-sections": [
+    { "type": "feat", "section": "Features" },
+    { "type": "feature", "section": "Features" },
+    { "type": "fix", "section": "Bug Fixes" },
+    { "type": "perf", "section": "Performance Improvements" },
+    { "type": "revert", "section": "Reverts" },
+    { "type": "docs", "section": "Documentation" },
+    { "type": "style", "section": "Styles" },
+    { "type": "chore", "section": "Miscellaneous Chores" },
+    { "type": "refactor", "section": "Code Refactoring" },
+    { "type": "test", "section": "Tests" },
+    { "type": "build", "section": "Build System" },
+    { "type": "ci", "section": "Continuous Integration" }
+  ],
+  "bump-minor-pre-major": true,
+  "bump-patch-for-minor-pre-major": true,
+  "include-v-in-tag": true,
+  "include-component-in-tag": false,
+  "pull-request-title-pattern": "chore: release ${version}"
+}
diff --git a/src/main/java/ch/heigvd/dai/Main.java b/src/main/java/ch/heigvd/dai/Main.java
index 135a531..c73999e 100644
--- a/src/main/java/ch/heigvd/dai/Main.java
+++ b/src/main/java/ch/heigvd/dai/Main.java
@@ -1,7 +1,31 @@
 package ch.heigvd.dai;
 
+import ch.heigvd.dai.commands.Root;
+import java.io.File;
+import picocli.CommandLine;
+
 public class Main {
   public static void main(String[] args) {
-    System.out.println("Hello world!");
+    // Example from class -
+    // https://github.com/heig-vd-dai-course/heig-vd-dai-course-java-ios-practical-content-template/blob/778e1934a64f338e93613afbb31dd9e92356d7c4/src/main/java/ch/heigvd/dai/Main.java#L10
+    // Define command name - source: https://stackoverflow.com/a/11159435
+    String jarFilename =
+        new File(Main.class.getProtectionDomain().getCodeSource().getLocation().getPath())
+            .getName();
+
+    // Create root command and CommandLine
+    CommandLine command = new CommandLine(new Root());
+    command.setCommandName(jarFilename).setCaseInsensitiveEnumValuesAllowed(true);
+
+    // Calculate execution time for root command and its subcommands
+    Long start = System.nanoTime();
+    int exitCode = command.execute(args);
+    Long end = System.nanoTime();
+
+    if (exitCode == 0) {
+      System.out.println("Execution time: " + (end - start) / (1000 * 1000) + " ms");
+    }
+
+    System.exit(exitCode);
   }
 }
diff --git a/src/main/java/ch/heigvd/dai/MessageManipulator.java b/src/main/java/ch/heigvd/dai/MessageManipulator.java
deleted file mode 100644
index 625b444..0000000
--- a/src/main/java/ch/heigvd/dai/MessageManipulator.java
+++ /dev/null
@@ -1,103 +0,0 @@
-/*
- * @brief   Class provides functions to manipulate messages, whether it means hiding or exposing it
- * @class   DAI
- * @pw      1
- * @authors Pedro Alves da Silva, Gonçalo Heleno Carvalheiro
- * Copyright (c) 2024
- */
-
-package ch.heigvd.dai;
-
-import ch.heigvd.dai.exceptions.MessageManipulationException;
-
-import static ch.heigvd.dai.BmpFile.*;
-
-public class MessageManipulator
-{
-	/**
-	 * Hides a provided message inside the provided data array
-	 *
-	 * @param bmpFile     Parsed bitmap file instance
-	 * @param message     Message to hide
-	 * @param bitsPerByte Number of bits to use per message byte
-	 * @throws MessageManipulationException Raised in case one of the arguments is not valid
-	 * @implNote Data array is used as input and output. Each of the (bitsPerByte) LSb of each byte in data are replaced
-	 */
-	public void hideMessage(BmpFile bmpFile, byte[] message, int bitsPerByte) throws MessageManipulationException
-	{
-		byte[] data = bmpFile.getPixelArray();
-
-		if (bitsPerByte < MIN_BITS_PER_BYTE || bitsPerByte > MAX_BITS_PER_BYTE)
-		{
-			throw new MessageManipulationException("Bit count must be between " + MIN_BITS_PER_BYTE + " and " + MAX_BITS_PER_BYTE);
-		} /* if */
-
-		if (message.length < MIN_MESSAGE_LENGTH || message.length > MAX_MESSAGE_LENGTH)
-		{
-			throw new MessageManipulationException("Invalid message length");
-		} /* if */
-
-		// 8 bytes in pixel array to store 1 byte of message
-		if (data.length < message.length * MAX_BITS_PER_BYTE)
-		{
-			throw new MessageManipulationException("Not enough space to hide message in data");
-		} /* if */
-
-		// Mask used to reset the data bits to hide the message in
-		byte bit_mask = (byte) ((1 << bitsPerByte) - 1);
-
-		// Bit by bit in message, byte by byte in pixel array
-		for (int i = 0; i < message.length * MAX_BITS_PER_BYTE; ++i)
-		{
-			int bit_offset = i % MAX_BITS_PER_BYTE;
-			int msg_offset = i >> 3;
-			byte msg_byte = message[msg_offset];
-			byte msg_bit = (byte) ((msg_byte >> (MAX_BITS_PER_BYTE - 1 - bit_offset)) & bit_mask);
-			data[i] &= (byte) ~bit_mask;
-			data[i] |= msg_bit;
-		} /* for */
-
-		bmpFile.setData(data, message.length, bitsPerByte);
-	}
-
-	/**
-	 * Extracts a hidden message from the provided data array
-	 *
-	 * @param bmpFile Parsed bitmap file instance
-	 * @param message Message extracted
-	 * @throws MessageManipulationException Raised in case one of the arguments is not valid
-	 * @implNote Data array is used as input and output. Each of the (bitsPerByte) LSb of each byte in data are set to 0
-	 */
-	public void exposeMessage(BmpFile bmpFile, byte[] message) throws MessageManipulationException
-	{
-		int bitsPerByte = bmpFile.getBitsPerByte();
-		int messageLength = bmpFile.getMessageLength();
-		byte[] data = bmpFile.getPixelArray();
-
-		// 8 bytes in pixel array to store 1 byte of message
-		if (data.length < message.length * MAX_BITS_PER_BYTE)
-		{
-			throw new MessageManipulationException("Data is not enough to retrieve hidden message");
-		} /* if */
-
-		// Mask used to reset the data bits to hide the message in
-		byte bit_mask = (byte) ((1 << bitsPerByte) - 1);
-
-		// Bit by bit in message, byte by byte in pixel array
-		for (int i = 0; i < messageLength * MAX_BITS_PER_BYTE; ++i)
-		{
-			int bit_offset = i % MAX_BITS_PER_BYTE;
-			int byte_offset = i >> 3;
-			byte pixel = data[i];
-			byte hidden_bit = (byte) (pixel & bit_mask);
-
-			// Reset data bits
-			data[i] = (byte) (pixel ^ hidden_bit);
-
-			// Extract message
-			message[byte_offset] |= (byte) (hidden_bit << (MAX_BITS_PER_BYTE - 1 - bit_offset));
-		} /* for */
-
-		bmpFile.setData(data, 0, 0);
-	}
-}
diff --git a/src/main/java/ch/heigvd/dai/commands/Expose.java b/src/main/java/ch/heigvd/dai/commands/Expose.java
new file mode 100644
index 0000000..1c27801
--- /dev/null
+++ b/src/main/java/ch/heigvd/dai/commands/Expose.java
@@ -0,0 +1,64 @@
+package ch.heigvd.dai.commands;
+
+import ch.heigvd.dai.utilities.BmpFile;
+import ch.heigvd.dai.utilities.FileManipulator;
+import ch.heigvd.dai.utilities.MessageManipulator;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.concurrent.Callable;
+import picocli.CommandLine;
+
+@CommandLine.Command(
+    name = "expose",
+    description = "Expose an hidden file/message from a BMP image.")
+public class Expose implements Callable<Integer> {
+  @CommandLine.ParentCommand private Root parent;
+
+  @Override
+  public Integer call() {
+    if (Files.exists(Paths.get(parent.getFilenameMessage()))) {
+      if (Files.isDirectory(Paths.get(parent.getFilenameMessage()))) {
+        System.err.println(
+            "The path for the message output is a directory.\n"
+                + "Please provide a different path.");
+        return 1;
+      }
+      if (parent.forceDisabled()) {
+        System.err.println(
+            "A file already exists on the output path provided.\n"
+                + "If you are sure you want to overwrite that file, enable the '--force' flag.");
+        return 1;
+      }
+    }
+
+    if (!parent.isBmpFileValid()) {
+      System.err.println(
+          "BMP file provided either does not exist or is a directory.\n"
+              + "Please provide a path to a valid BMP file.");
+      return 1;
+    }
+
+    try {
+      BmpFile bmpFile = new BmpFile(parent.getFilenameBmpImage());
+
+      if (!bmpFile.hasMessage()) {
+        System.err.println(
+            "BMP file provided does not have a message hidden inside.\n"
+                + "Please provide a path to a BMP file containing a message.");
+        return 1;
+      }
+
+      byte[] message = new byte[bmpFile.getMessageLength()];
+      FileManipulator fileManipulator = new FileManipulator(parent.getFilenameMessage(), true);
+      MessageManipulator messageManipulator = new MessageManipulator();
+
+      messageManipulator.exposeMessage(bmpFile, message);
+      fileManipulator.writeBytesToFile(message);
+    } catch (Exception e) {
+      System.err.println("Error while hiding message! Exception message:\n" + e.getMessage());
+      return 1;
+    }
+
+    return 0;
+  }
+}
diff --git a/src/main/java/ch/heigvd/dai/commands/Hide.java b/src/main/java/ch/heigvd/dai/commands/Hide.java
new file mode 100644
index 0000000..38cdfe3
--- /dev/null
+++ b/src/main/java/ch/heigvd/dai/commands/Hide.java
@@ -0,0 +1,85 @@
+package ch.heigvd.dai.commands;
+
+import ch.heigvd.dai.utilities.BmpFile;
+import ch.heigvd.dai.utilities.FileManipulator;
+import ch.heigvd.dai.utilities.MessageManipulator;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.concurrent.Callable;
+import picocli.CommandLine;
+
+@CommandLine.Command(
+    name = "hide",
+    description = "Hide the bits of a message/file into a BMP image.")
+public class Hide implements Callable<Integer> {
+  @CommandLine.ParentCommand private Root parent;
+
+  @CommandLine.Parameters(
+      index = "0",
+      description = "The filename where the image with the hidden content will be stored.",
+      defaultValue = "output.bmp")
+  private String filenameOutput;
+
+  @CommandLine.Option(
+      names = {"-b", "--bits-per-byte"},
+      description =
+          "Number of bits to hide per byte of information of the BMP image. Note that the original bits of the image will be overwritten and it may be more noticeable that something is hidden within the image.",
+      defaultValue = "1")
+  private int bitsPerByte;
+
+  @Override
+  public Integer call() {
+    if (!isPowerOfTwo(bitsPerByte) || bitsPerByte < 1 || bitsPerByte > 8) {
+      System.err.println("--bits-per-byte needs to be a power of 2 between 1 and 8 inclusively");
+      return 1;
+    }
+
+    if (parent.forceDisabled() && Files.exists(Paths.get(filenameOutput))) {
+      System.err.println(
+          "A file already exists on the output path provided.\n"
+              + "If you are sure you want to overwrite it, enable the '--force' flag.");
+      return 1;
+    }
+
+    if (!parent.isMessageFileValid()) {
+      System.err.println(
+          "Message file either does not exist or is a directory.\n"
+              + "Please provide a path to a valid file.");
+      return 1;
+    }
+
+    if (!parent.isBmpFileValid()) {
+      System.err.println(
+          "BMP file provided either does not exist or is a directory.\n"
+              + "Please provide a path to a valid BMP file.");
+      return 1;
+    }
+
+    try {
+      BmpFile bmpFile = new BmpFile(parent.getFilenameBmpImage());
+
+      if (parent.forceDisabled() && bmpFile.hasMessage()) {
+        System.err.println(
+            "BMP file provided already has a message hidden inside.\n"
+                + "If you are sure you want to overwrite it, enable the '--force' flag.");
+        return 1;
+      }
+
+      FileManipulator fileManipulator = new FileManipulator(parent.getFilenameMessage());
+      MessageManipulator messageManipulator = new MessageManipulator();
+
+      messageManipulator.hideMessage(bmpFile, fileManipulator.readBytesFromFile(), bitsPerByte);
+      bmpFile.saveFile(filenameOutput);
+    } catch (Exception e) {
+      System.err.println("Error while hiding message! Exception message:\n" + e.getMessage());
+      return 1;
+    }
+
+    return 0;
+  }
+
+  // Ref: https://www.baeldung.com/java-check-number-power-of-two
+  private boolean isPowerOfTwo(int n) {
+    return (n != 0) && ((n & (n - 1)) == 0);
+  }
+}
diff --git a/src/main/java/ch/heigvd/dai/commands/Root.java b/src/main/java/ch/heigvd/dai/commands/Root.java
new file mode 100644
index 0000000..d2610b6
--- /dev/null
+++ b/src/main/java/ch/heigvd/dai/commands/Root.java
@@ -0,0 +1,66 @@
+package ch.heigvd.dai.commands;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import picocli.CommandLine;
+
+@CommandLine.Command(
+    description = "shadow - a CLI tool to hide files inside BMP images",
+    version = "0.0.1",
+    subcommands = {
+      Hide.class,
+      Expose.class,
+    },
+    scope = CommandLine.ScopeType.INHERIT,
+    mixinStandardHelpOptions = true)
+public class Root {
+
+  @CommandLine.Parameters(
+      index = "0",
+      description =
+          "The BMP image where the content will be hidden or where to read the content from.")
+  private String filenameBmpImage;
+
+  @CommandLine.Parameters(
+      index = "1",
+      description =
+          "The file where to read the message from or the file destination where to write the message to, depending on the operation mode.")
+  private String filenameMessage;
+
+  @CommandLine.Option(
+      names = {"-f", "--force"},
+      description = "Overwrite output file if something already exists in the path.")
+  private boolean force;
+
+  // TODO Remove the following block if not implemented
+  //
+  //  @CommandLine.Option(
+  //      names = {"-e", "--encryption-key"},
+  //      description =
+  //          "The GPG encryption key to use to encrypt the message/file before hiding it inside the
+  // BMP image.")
+  //  protected String encryptionKey;
+
+  public String getFilenameBmpImage() {
+    return filenameBmpImage;
+  }
+
+  public String getFilenameMessage() {
+    return filenameMessage;
+  }
+
+  public boolean forceDisabled() {
+    return !force;
+  }
+
+  public boolean isBmpFileValid() {
+    Path path = Paths.get(filenameBmpImage);
+    return Files.exists(path) && !Files.isDirectory(path);
+  }
+
+  public boolean isMessageFileValid() {
+    Path path = Paths.get(filenameMessage);
+    return Files.exists(path) && !Files.isDirectory(path);
+  }
+}
diff --git a/src/main/java/ch/heigvd/dai/exceptions/MessageManipulationException.java b/src/main/java/ch/heigvd/dai/exceptions/MessageManipulationException.java
index 9450d34..ec3f788 100644
--- a/src/main/java/ch/heigvd/dai/exceptions/MessageManipulationException.java
+++ b/src/main/java/ch/heigvd/dai/exceptions/MessageManipulationException.java
@@ -8,10 +8,8 @@
 
 package ch.heigvd.dai.exceptions;
 
-public class MessageManipulationException extends IllegalArgumentException
-{
-	public MessageManipulationException(String s)
-	{
-		super(String.format("Exception thrown while manipulating message: %s", s));
-	}
+public class MessageManipulationException extends IllegalArgumentException {
+  public MessageManipulationException(String s) {
+    super(String.format("Exception thrown while manipulating message: %s", s));
+  }
 }
diff --git a/src/main/java/ch/heigvd/dai/BmpFile.java b/src/main/java/ch/heigvd/dai/utilities/BmpFile.java
similarity index 99%
rename from src/main/java/ch/heigvd/dai/BmpFile.java
rename to src/main/java/ch/heigvd/dai/utilities/BmpFile.java
index 105cb04..3c0365f 100644
--- a/src/main/java/ch/heigvd/dai/BmpFile.java
+++ b/src/main/java/ch/heigvd/dai/utilities/BmpFile.java
@@ -4,7 +4,7 @@
  * @pw 1
  * @authors Pedro Alves da Silva, Gonçalo Heleno Carvalheiro Copyright (c) 2024
  */
-package ch.heigvd.dai;
+package ch.heigvd.dai.utilities;
 
 import ch.heigvd.dai.exceptions.BmpFileException;
 import java.io.BufferedInputStream;
diff --git a/src/main/java/ch/heigvd/dai/utilities/FileManipulator.java b/src/main/java/ch/heigvd/dai/utilities/FileManipulator.java
new file mode 100644
index 0000000..a392c3d
--- /dev/null
+++ b/src/main/java/ch/heigvd/dai/utilities/FileManipulator.java
@@ -0,0 +1,56 @@
+package ch.heigvd.dai.utilities;
+
+import java.io.BufferedInputStream;
+import java.io.BufferedOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+public class FileManipulator {
+
+  private final File file;
+
+  private boolean writeEnabled = false;
+
+  public FileManipulator(String filename) throws NullPointerException {
+    file = new File(filename);
+  }
+
+  public FileManipulator(String filename, boolean writeEnabled) throws NullPointerException {
+    this(filename);
+    this.writeEnabled = writeEnabled;
+  }
+
+  public byte[] readBytesFromFile() throws IOException, Exception {
+    long fileSize = this.file.length();
+
+    // A byte array cannot hold more than 2ˆ31 - 1 values.
+    if (fileSize >= Integer.MAX_VALUE)
+      throw new OutOfMemoryError("The message file is too big for byte[] array.");
+
+    byte[] bytes = new byte[(int) fileSize];
+
+    try (FileInputStream fileInputStream = new FileInputStream(file);
+        BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream)) {
+      int bytesRead = bufferedInputStream.read(bytes);
+      if (bytesRead != fileSize) {
+        throw new RuntimeException("Error while reading from the buffer to the byte[] array.");
+      }
+    }
+
+    return bytes;
+  }
+
+  public void writeBytesToFile(byte[] bytes) throws Exception, IOException {
+    if (!writeEnabled)
+      throw new RuntimeException(
+          "Unable to write to file, because write operations are not activated for this object.");
+
+    try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream)) {
+      bufferedOutputStream.write(bytes);
+      bufferedOutputStream.flush();
+    }
+  }
+}
diff --git a/src/main/java/ch/heigvd/dai/utilities/MessageManipulator.java b/src/main/java/ch/heigvd/dai/utilities/MessageManipulator.java
new file mode 100644
index 0000000..c019b94
--- /dev/null
+++ b/src/main/java/ch/heigvd/dai/utilities/MessageManipulator.java
@@ -0,0 +1,98 @@
+/*
+ * @brief   Class provides functions to manipulate messages, whether it means hiding or exposing it
+ * @class   DAI
+ * @pw      1
+ * @authors Pedro Alves da Silva, Gonçalo Heleno Carvalheiro
+ * Copyright (c) 2024
+ */
+
+package ch.heigvd.dai.utilities;
+
+import static ch.heigvd.dai.utilities.BmpFile.*;
+
+import ch.heigvd.dai.exceptions.MessageManipulationException;
+
+public class MessageManipulator {
+  /**
+   * Hides a provided message inside the provided data array
+   *
+   * @param bmpFile Parsed bitmap file instance
+   * @param message Message to hide
+   * @param bitsPerByte Number of bits to use per message byte
+   * @throws MessageManipulationException Raised in case one of the arguments is not valid
+   * @implNote Data array is used as input and output. Each of the (bitsPerByte) LSb of each byte in
+   *     data are replaced
+   */
+  public void hideMessage(BmpFile bmpFile, byte[] message, int bitsPerByte)
+      throws MessageManipulationException {
+    byte[] data = bmpFile.getPixelArray();
+
+    if (bitsPerByte < MIN_BITS_PER_BYTE || bitsPerByte > MAX_BITS_PER_BYTE) {
+      throw new MessageManipulationException(
+          "Bit count must be between " + MIN_BITS_PER_BYTE + " and " + MAX_BITS_PER_BYTE);
+    } /* if */
+
+    if (message.length < MIN_MESSAGE_LENGTH || message.length > MAX_MESSAGE_LENGTH) {
+      throw new MessageManipulationException("Invalid message length");
+    } /* if */
+
+    // 8 bytes in pixel array to store 1 byte of message
+    if (data.length < message.length * MAX_BITS_PER_BYTE) {
+      throw new MessageManipulationException("Not enough space to hide message in data");
+    } /* if */
+
+    // Mask used to reset the data bits to hide the message in
+    byte bit_mask = (byte) ((1 << bitsPerByte) - 1);
+
+    // Bit by bit in message, byte by byte in pixel array
+    for (int i = 0; i < message.length * MAX_BITS_PER_BYTE; ++i) {
+      int bit_offset = i % MAX_BITS_PER_BYTE;
+      int msg_offset = i >> 3;
+      byte msg_byte = message[msg_offset];
+      byte msg_bit = (byte) ((msg_byte >> (MAX_BITS_PER_BYTE - 1 - bit_offset)) & bit_mask);
+      data[i] &= (byte) ~bit_mask;
+      data[i] |= msg_bit;
+    } /* for */
+
+    bmpFile.setData(data, message.length, bitsPerByte);
+  }
+
+  /**
+   * Extracts a hidden message from the provided data array
+   *
+   * @param bmpFile Parsed bitmap file instance
+   * @param message Message extracted
+   * @throws MessageManipulationException Raised in case one of the arguments is not valid
+   * @implNote Data array is used as input and output. Each of the (bitsPerByte) LSb of each byte in
+   *     data are set to 0
+   */
+  public void exposeMessage(BmpFile bmpFile, byte[] message) throws MessageManipulationException {
+    int bitsPerByte = bmpFile.getBitsPerByte();
+    int messageLength = bmpFile.getMessageLength();
+    byte[] data = bmpFile.getPixelArray();
+
+    // 8 bytes in pixel array to store 1 byte of message
+    if (data.length < message.length * MAX_BITS_PER_BYTE) {
+      throw new MessageManipulationException("Data is not enough to retrieve hidden message");
+    } /* if */
+
+    // Mask used to reset the data bits to hide the message in
+    byte bit_mask = (byte) ((1 << bitsPerByte) - 1);
+
+    // Bit by bit in message, byte by byte in pixel array
+    for (int i = 0; i < messageLength * MAX_BITS_PER_BYTE; ++i) {
+      int bit_offset = i % MAX_BITS_PER_BYTE;
+      int byte_offset = i >> 3;
+      byte pixel = data[i];
+      byte hidden_bit = (byte) (pixel & bit_mask);
+
+      // Reset data bits
+      data[i] = (byte) (pixel ^ hidden_bit);
+
+      // Extract message
+      message[byte_offset] |= (byte) (hidden_bit << (MAX_BITS_PER_BYTE - 1 - bit_offset));
+    } /* for */
+
+    bmpFile.setData(data, 0, 0);
+  }
+}
diff --git a/test_files/bmp_source.bmp b/test_files/bmp_source.bmp
new file mode 100755
index 0000000..02242b9
Binary files /dev/null and b/test_files/bmp_source.bmp differ
diff --git a/test_files/message_video.mp4 b/test_files/message_video.mp4
new file mode 100644
index 0000000..ce2928b
Binary files /dev/null and b/test_files/message_video.mp4 differ
diff --git a/test_files/test_message_from_bmp.mp4 b/test_files/test_message_from_bmp.mp4
new file mode 100644
index 0000000..ce2928b
Binary files /dev/null and b/test_files/test_message_from_bmp.mp4 differ
diff --git a/test_files/test_output_hidden_message.bmp b/test_files/test_output_hidden_message.bmp
new file mode 100644
index 0000000..2ee8bb0
Binary files /dev/null and b/test_files/test_output_hidden_message.bmp differ