diff --git a/src/fr/univ/lyon1/server/ConnectedClient.java b/src/fr/univ/lyon1/server/ConnectedClient.java
index cb3e226..f6082b7 100644
--- a/src/fr/univ/lyon1/server/ConnectedClient.java
+++ b/src/fr/univ/lyon1/server/ConnectedClient.java
@@ -17,6 +17,9 @@ import java.net.Socket;
 import java.util.Collections;
 import java.util.List;
 
+/**
+ * Server client connection management
+ */
 public class ConnectedClient implements Runnable {
     private static int idCounter = 0;
     private final int id = idCounter++;
@@ -26,6 +29,12 @@ public class ConnectedClient implements Runnable {
     private ObjectInputStream in;
     private UserModel user;
 
+    /**
+     * Create a client connection management
+     * @param server server socket
+     * @param socket client socket
+     * @throws IOException if a connection error occur with the client
+     */
     ConnectedClient(Server server, Socket socket) throws IOException {
         this.server = server;
         this.socket = socket;
@@ -33,12 +42,31 @@ public class ConnectedClient implements Runnable {
         this.in = new ObjectInputStream(socket.getInputStream());
     }
 
-    public Message sendMessage(Message message) throws IOException {
-        out.writeObject(new Command(CommandType.message, List.of(message)));
+    /**
+     * Send command to the client
+     * @param cmd the command
+     * @throws IOException if a connection error occur with the client
+     */
+    private void send(Command cmd) throws IOException {
+        out.writeObject(cmd);
         out.flush();
-        return message;
     }
 
+    /**
+     * Send a message to the client
+     * @param message the message
+     * @throws IOException if a connection error occur with the client
+     */
+    public void sendMessage(Message message) throws IOException {
+        send(new Command(CommandType.message, List.of(message)));
+    }
+
+    /**
+     * Client command handler
+     * @param command the command
+     * @throws IOException if a connection error occur with the client
+     * @throws ChatException chat runtime error send to the user
+     */
     private void actionCommand(Command command) throws IOException, ChatException {
         CommandType type = command.getType();
         if (user == null && type != CommandType.login)
@@ -53,7 +81,14 @@ public class ConnectedClient implements Runnable {
         }
     }
 
-    private void commandLogin(Command cmd) throws IOException, ChatException {
+    /**
+     * Handel's user authentication
+     * ToDo avoid re auth
+     * @param cmd the login command
+     * @throws IOException if a connection error occur with the client
+     * @throws LoginInvalid if the user credentials are invalid
+     */
+    private void commandLogin(Command cmd) throws IOException, LoginInvalid {
         List<Object> args = cmd.getArgs();
 
         String username = (String) args.get(0);
@@ -71,13 +106,17 @@ public class ConnectedClient implements Runnable {
         else if (!user.checkPassword(password))
             throw new LoginInvalid("Password invalid");
         else {
-            out.writeObject(new Command(CommandType.login, null));
-            out.flush();
+            send(new Command(CommandType.login, null));
             this.user = user;
             System.out.println("Client "+user.getUsername()+" is connected !");
         }
     }
 
+    /**
+     * Message receive handler
+     * @param cmd the message command
+     * @throws NotInChannel if the user is not in the channel
+     */
     private void commandMessage(Command cmd) throws NotInChannel {
         Message msg = (Message) cmd.getArgs().get(0);
         msg.setSender(this.user);
@@ -89,16 +128,27 @@ public class ConnectedClient implements Runnable {
             server.broadcastMessage(msg, id);
     }
 
+    /**
+     * Command user list handler
+     * @throws IOException if a connection error occur with the client
+     */
     private void commandList() throws IOException {
-        out.writeObject(new Command(CommandType.list, Collections.singletonList(server.getUsers())));
-        out.flush();
+        send(new Command(CommandType.list, Collections.singletonList(server.getUsers())));
     }
 
+    /**
+     * Command channel list handler
+     * @throws IOException if a connection error occur with the client
+     */
     private void commandListChannels() throws IOException {
-        out.writeObject(new Command(CommandType.listChannels, Collections.singletonList((List<Channel>)(List<?>) ChannelModel.getAll())));
-        out.flush();
+        send(new Command(CommandType.listChannels, Collections.singletonList((List<Channel>)(List<?>) ChannelModel.getAll())));
     }
 
+    /**
+     * Channel join command handler
+     * @param cmd the join command
+     * @throws IOException if a connection error occur with the client
+     */
     private void commandJoin(Command cmd) throws IOException {
         String name = (String) cmd.getArgs().get(0);
         ChannelModel chan = ChannelModel.get(name);
@@ -110,12 +160,14 @@ public class ConnectedClient implements Runnable {
             if (!chan.have(user))
                 chan.addUser(user);
 
-        out.writeObject(new Command(CommandType.join, List.of((Channel) chan)));
-        out.flush();
+        send(new Command(CommandType.join, List.of((Channel) chan)));
 
         server.broadcastMessage(new Message(chan, Server.getServerUser(), user.getUsername()+" joined the channel !"), -1);
     }
 
+    /**
+     * Man thread of user connection
+     */
     public void run() {
         try {
             while (true) {
@@ -143,6 +195,10 @@ public class ConnectedClient implements Runnable {
         }
     }
 
+    /**
+     * Close connection to client
+     * @throws IOException if a connection error occur with the client
+     */
     public void closeClient() throws IOException {
         if (in != null)
             in.close();
@@ -150,10 +206,18 @@ public class ConnectedClient implements Runnable {
         socket.close();
     }
 
+    /**
+     * Get the client connection id
+     * @return connection id
+     */
     public int getId() {
         return id;
     }
 
+    /**
+     * Get the user
+     * @return the user
+     */
     public User getUser() {
         return user;
     }
diff --git a/src/fr/univ/lyon1/server/Connection.java b/src/fr/univ/lyon1/server/Connection.java
index 251f763..4bafda9 100644
--- a/src/fr/univ/lyon1/server/Connection.java
+++ b/src/fr/univ/lyon1/server/Connection.java
@@ -7,15 +7,28 @@ import java.io.IOException;
 import java.net.ServerSocket;
 import java.net.Socket;
 
+/**
+ * Server connection manager
+ */
 public class Connection implements Runnable {
     private final Server server;
     private final ServerSocket serverSocket;
 
+    /**
+     * Create a server connection manager
+     * @param server the server
+     * @throws IOException if a connection error occur with the client
+     */
     Connection(Server server) throws IOException {
         this.server = server;
         this.serverSocket = initSSL();
     }
 
+    /**
+     * Initialise the SSL client WebSocket connection
+     * @return the socket
+     * @throws IOException if a connection error occur with the client
+     */
     private SSLServerSocket initSSL() throws IOException {
 
         SSLContext ctx = ChatSSL.getSSLContext();
@@ -29,6 +42,9 @@ public class Connection implements Runnable {
         return sslListener;
     }
 
+    /**
+     * Main thread
+     */
     public void run() {
         while (true) {
             Socket clientSocket;
diff --git a/src/fr/univ/lyon1/server/Database.java b/src/fr/univ/lyon1/server/Database.java
index 8756122..cbd41ce 100644
--- a/src/fr/univ/lyon1/server/Database.java
+++ b/src/fr/univ/lyon1/server/Database.java
@@ -10,10 +10,16 @@ import java.sql.DriverManager;
 import java.sql.SQLException;
 import java.util.Properties;
 
+/**
+ * Server database management
+ */
 public class Database {
     private static Database database;
     private Connection connection;
 
+    /**
+     * Create database object and establish connection
+     */
     private Database() {
         Database.database = this;
         try {
@@ -26,7 +32,12 @@ public class Database {
         init();
     }
 
-    private String[] getCredentials() throws NullPointerException, IOException {
+    /**
+     * Get database credentials
+     * @return credentials
+     * @throws IOException when an error occur with the configuration file
+     */
+    private String[] getCredentials() throws IOException {
         Properties props = new Properties();
         File f = new File("server.properties");
 
@@ -43,6 +54,12 @@ public class Database {
         return new String[]{props.getProperty("db.url"), props.getProperty("db.user"), props.getProperty("db.password")};
     }
 
+    /**
+     * Get the database connection
+     * @return the connection
+     * @throws SQLException if a connection error occur with the database
+     * @throws IOException when failed to get the credentials
+     */
     private Connection getConnexion() throws SQLException, IOException {
         String[] credentials = getCredentials();
 
@@ -56,16 +73,27 @@ public class Database {
         return DriverManager.getConnection(credentials[0], credentials[1], credentials[2]);
     }
 
+    /**
+     * Get the database connection
+     * @return the connection
+     */
     public Connection getConnection() {
         return connection;
     }
 
+    /**
+     * Get the database instance
+     * @return the database
+     */
     public static Database getDatabase() {
         if (Database.database == null)
             return new Database();
         return Database.database;
     }
 
+    /**
+     * Initialise the database tables from models
+     */
     private void init() {
         UserModel.generateTable();
         ChannelModel.generateTable();
diff --git a/src/fr/univ/lyon1/server/MainServer.java b/src/fr/univ/lyon1/server/MainServer.java
index 5809841..a479b62 100644
--- a/src/fr/univ/lyon1/server/MainServer.java
+++ b/src/fr/univ/lyon1/server/MainServer.java
@@ -2,6 +2,9 @@ package fr.univ.lyon1.server;
 
 import java.io.IOException;
 
+/**
+ * Main server program
+ */
 public class MainServer {
     public static void main(String[] args) {
         try {
@@ -16,6 +19,9 @@ public class MainServer {
         }
     }
 
+    /**
+     * Help usage for arguments
+     */
     private static void printUsage() {
         System.out.println("java server.Server <port>");
         System.out.println("\t<port>: server's port");
diff --git a/src/fr/univ/lyon1/server/Server.java b/src/fr/univ/lyon1/server/Server.java
index 8bf6058..411d6a2 100644
--- a/src/fr/univ/lyon1/server/Server.java
+++ b/src/fr/univ/lyon1/server/Server.java
@@ -9,11 +9,19 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.UUID;
 
+/**
+ * Main server management
+ */
 public class Server {
     private final int port;
-    private List<ConnectedClient> clients = new ArrayList<>();
-    private static User serverUser = new User(UUID.fromString("3539b6bf-5eb3-41d4-893f-cbf0caa9ca74"), "server");
+    private final List<ConnectedClient> clients = new ArrayList<>();
+    private static final User serverUser = new User(UUID.fromString("3539b6bf-5eb3-41d4-893f-cbf0caa9ca74"), "server");
 
+    /**
+     * Create server
+     * @param port the listening port
+     * @throws IOException if a connection error occur
+     */
     Server(int port) throws IOException {
         this.port = port;
         Database.getDatabase();
@@ -21,12 +29,20 @@ public class Server {
         connection.start();
     }
 
-    public ConnectedClient addClient(ConnectedClient newClient) {
+    /**
+     * Add client handler
+     * @param newClient the client
+     */
+    public void addClient(ConnectedClient newClient) {
         clients.add(newClient);
-        return newClient;
     }
 
-    public int broadcastMessage(Message message, int id) {
+    /**
+     * Send a message to all clients
+     * @param message the message
+     * @param id the sender id
+     */
+    public void broadcastMessage(Message message, int id) {
         List<UUID> users = UserChannelModel.getUsers(message.getChannel()).stream().map(User::getUUID).toList();
         for (ConnectedClient client : clients.stream().filter(connectedClient -> users.contains(connectedClient.getUser().getUUID())).toList()) {
             if (id == -1 || client.getId() != id)
@@ -37,10 +53,13 @@ public class Server {
                     e.printStackTrace();
                 }
         }
-        return id;
     }
 
-    public ConnectedClient disconnectedClient(ConnectedClient client) {
+    /**
+     * Close client connection
+     * @param client the client connection manager
+     */
+    public void disconnectedClient(ConnectedClient client) {
         try {
             client.closeClient();
         } catch (IOException e) {
@@ -51,17 +70,28 @@ public class Server {
         clients.remove(client);
 
         System.out.println("Client "+client.getId()+" disconnected");
-        return client;
     }
 
+    /**
+     * Get the server listening port
+     * @return the server listening port
+     */
     public int getPort() {
         return port;
     }
 
+    /**
+     * Get the server user
+     * @return the server user
+     */
     public static User getServerUser() {
         return serverUser;
     }
 
+    /**
+     * Get the list of connection client to the server
+     * @return list of connected client to the server
+     */
     public List<User> getUsers() {
         return clients.stream().map(ConnectedClient::getUser).toList();
     }
diff --git a/src/fr/univ/lyon1/server/models/ChannelModel.java b/src/fr/univ/lyon1/server/models/ChannelModel.java
index 111ee31..4429ffa 100644
--- a/src/fr/univ/lyon1/server/models/ChannelModel.java
+++ b/src/fr/univ/lyon1/server/models/ChannelModel.java
@@ -10,26 +10,53 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.UUID;
 
+/**
+ * Database model of a channel
+ */
 public class ChannelModel extends Channel implements Model {
     private static final String TABLE_NAME = "Channel";
 
+    /**
+     * Create a new channel from a name
+     * @param name the name
+     */
     public ChannelModel(String name) {
         super(name);
         create();
     }
 
+    /**
+     * Model from existing channel
+     * @param uuid
+     * @param name
+     */
     private ChannelModel(UUID uuid, String name) {
         super(uuid, name);
     }
 
+    /**
+     * Add a user to the channel
+     * ToDo on user reconnection rejoin all connected channels
+     * @param user the user
+     */
     public void addUser(User user) {
         new UserChannelModel(user, this);
     }
 
+    /**
+     * Check if a user is in this channel
+     * @param user the user
+     * @return true if is else false
+     */
     public boolean have(User user) {
         return UserChannelModel.exist(user, this);
     }
 
+    /**
+     * Get a channel from a name
+     * @param name the name
+     * @return the channel or null if not found
+     */
     public static ChannelModel get(String name) {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("SELECT UUID FROM "+TABLE_NAME+" WHERE name = ?");
@@ -46,6 +73,11 @@ public class ChannelModel extends Channel implements Model {
         return null;
     }
 
+    /**
+     * Get a channel from the unique id
+     * @param uuid the unique id
+     * @return the channel or null if not found
+     */
     public static ChannelModel get(UUID uuid) {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("SELECT * FROM "+TABLE_NAME+" WHERE UUID = ?");
@@ -65,6 +97,10 @@ public class ChannelModel extends Channel implements Model {
         return null;
     }
 
+    /**
+     * Get all channels
+     * @return a list of channels
+     */
     public static List<ChannelModel> getAll() {
         List<ChannelModel> channels = new ArrayList<>();
         try {
@@ -84,6 +120,10 @@ public class ChannelModel extends Channel implements Model {
         return channels;
     }
 
+    /**
+     * Check of the channel exists in the database
+     * @return true if the channel exists else false
+     */
     private boolean exist() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("SELECT UUID FROM "+TABLE_NAME+" WHERE UUID = ?");
@@ -96,6 +136,10 @@ public class ChannelModel extends Channel implements Model {
         }
     }
 
+    /**
+     * Register the channel in the database
+     * @return true if the register is successful else false
+     */
     private boolean create() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("INSERT INTO "+TABLE_NAME+" (UUID, name) VALUES (?, ?)");
@@ -108,6 +152,10 @@ public class ChannelModel extends Channel implements Model {
         }
     }
 
+    /**
+     * Update the channel in the database
+     * @return true if the update is successful else false
+     */
     public boolean save() {
         if (!exist())
             return create();
@@ -122,6 +170,9 @@ public class ChannelModel extends Channel implements Model {
         }
     }
 
+    /**
+     * Generate the channel model table in the database
+     */
     public static void generateTable() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("CREATE TABLE IF NOT EXISTS "+TABLE_NAME+" ( UUID varchar(40) primary key, name varchar(16) unique )");
diff --git a/src/fr/univ/lyon1/server/models/Model.java b/src/fr/univ/lyon1/server/models/Model.java
index 5903bdb..26c6dc3 100644
--- a/src/fr/univ/lyon1/server/models/Model.java
+++ b/src/fr/univ/lyon1/server/models/Model.java
@@ -2,7 +2,9 @@ package fr.univ.lyon1.server.models;
 
 import fr.univ.lyon1.server.Database;
 
-
+/**
+ * Base model of a database type
+ */
 public interface Model {
     Database database = Database.getDatabase();
 }
diff --git a/src/fr/univ/lyon1/server/models/UserChannelModel.java b/src/fr/univ/lyon1/server/models/UserChannelModel.java
index 8e7b728..e5dbd8b 100644
--- a/src/fr/univ/lyon1/server/models/UserChannelModel.java
+++ b/src/fr/univ/lyon1/server/models/UserChannelModel.java
@@ -10,12 +10,20 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.UUID;
 
+/**
+ * Database model of the relation between user and channel
+ */
 public class UserChannelModel implements Model {
     private User user;
     private Channel channel;
 
     private static final String TABLE_NAME = "UserChannel";
 
+    /**
+     * Create a user channel relation and save it in database if necessary
+     * @param user
+     * @param channel
+     */
     public UserChannelModel(User user, Channel channel) {
         this.user = user;
         this.channel = channel;
@@ -24,6 +32,11 @@ public class UserChannelModel implements Model {
             create();
     }
 
+    /**
+     * Get the list of users in a specific channel
+     * @param channel the channel
+     * @return the list of users
+     */
     public static List<User> getUsers(Channel channel) {
         List<User> users = new ArrayList<>();
 
@@ -42,6 +55,11 @@ public class UserChannelModel implements Model {
         return users;
     }
 
+    /**
+     * Get a list of channel where a user is in
+     * @param user the user
+     * @return the list of channels
+     */
     public static List<Channel> getChannels(User user) {
         List<Channel> channels = new ArrayList<>();
 
@@ -60,6 +78,12 @@ public class UserChannelModel implements Model {
         return channels;
     }
 
+    /**
+     * Check if the relation exists in the database
+     * @param user the user
+     * @param channel the channel
+     * @return true if present else false
+     */
     public static boolean exist(User user, Channel channel) {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("SELECT 1 FROM "+TABLE_NAME+" WHERE userUUID = ? AND channelUUID = ?");
@@ -73,6 +97,10 @@ public class UserChannelModel implements Model {
         }
     }
 
+    /**
+     * Save the ration in the database
+     * @return true if succeed else false
+     */
     private boolean create() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("INSERT INTO "+TABLE_NAME+" (userUUID, channelUUID) VALUES (?, ?)");
@@ -85,6 +113,9 @@ public class UserChannelModel implements Model {
         }
     }
 
+    /**
+     * Generate the user channel relation model table in the database
+     */
     public static void generateTable() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("CREATE TABLE IF NOT EXISTS "+TABLE_NAME+" (userUUID varchar(40) not null references User(UUID), channelUUID varchar(40) not null references Channel(UUID), PRIMARY KEY (userUUID, channelUUID))");
diff --git a/src/fr/univ/lyon1/server/models/UserModel.java b/src/fr/univ/lyon1/server/models/UserModel.java
index 4624640..9b720e5 100644
--- a/src/fr/univ/lyon1/server/models/UserModel.java
+++ b/src/fr/univ/lyon1/server/models/UserModel.java
@@ -17,6 +17,9 @@ import java.util.UUID;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+/**
+ * Database model of a user type
+ */
 public class UserModel extends User implements Model {
     private String passwordHash;
 
@@ -28,17 +31,33 @@ public class UserModel extends User implements Model {
     private static final Pattern LAYOUT = Pattern.compile("\\$1\\$(\\d\\d?)\\$(.{43})");
     private static final String TABLE_NAME = "User";
 
+    /**
+     * Create a new user
+     * @param username the username
+     * @param password the password
+     */
     public UserModel(String username, String password) {
         super(username);
         setPassword(password);
         create();
     }
 
+    /**
+     * Create an existing user
+     * @param uuid the unique id
+     * @param username the username
+     * @param passwordHash the password hash
+     */
     private UserModel(UUID uuid, String username, String passwordHash) {
         super(uuid, username);
         this.passwordHash = passwordHash;
     }
 
+    /**
+     * Get a user from his username
+     * @param username the username
+     * @return the user of null if not found
+     */
     public static UserModel get(String username) {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("SELECT UUID FROM "+TABLE_NAME+" WHERE username = ?");
@@ -55,6 +74,11 @@ public class UserModel extends User implements Model {
         return null;
     }
 
+    /**
+     * Get a user from his unique id
+     * @param uuid the unique id
+     * @return the user of null if not found
+     */
     public static UserModel get(UUID uuid) {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("SELECT * FROM "+TABLE_NAME+" WHERE UUID = ?");
@@ -75,6 +99,10 @@ public class UserModel extends User implements Model {
         return null;
     }
 
+    /**
+     * Check if the user exists in the database
+     * @return true if present else false
+     */
     private boolean exist() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("SELECT UUID FROM "+TABLE_NAME+" WHERE UUID = ?");
@@ -87,6 +115,10 @@ public class UserModel extends User implements Model {
         }
     }
 
+    /**
+     * Create a user in the database
+     * @return true if the update is successful else false
+     */
     private boolean create() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("INSERT INTO "+TABLE_NAME+" (UUID, username, password) VALUES (?, ?, ?)");
@@ -100,6 +132,10 @@ public class UserModel extends User implements Model {
         }
     }
 
+    /**
+     * Update a user in the database
+     * @return true if the update is successful else false
+     */
     public boolean save() {
         if (!exist())
             return create();
@@ -116,6 +152,9 @@ public class UserModel extends User implements Model {
         }
     }
 
+    /**
+     * Generate the channel model table in the database
+     */
     public static void generateTable() {
         try {
             PreparedStatement ps = database.getConnection().prepareStatement("CREATE TABLE IF NOT EXISTS "+TABLE_NAME+" ( UUID varchar(40) primary key, username varchar(16) unique, password varchar(256) )");
@@ -125,41 +164,77 @@ public class UserModel extends User implements Model {
         }
     }
 
+    /**
+     * Get the password hash
+     * @return password hash
+     */
     public String getPasswordHash() {
         return passwordHash;
     }
 
+    /**
+     * Set the password as a hash
+     * @param password the plain password
+     */
     public void setPassword(String password) {
+        // Generate a new salt
         byte[] passwordSalt = new byte[SIZE / 8];
         random.nextBytes(passwordSalt);
+
+        // Generate the hash from the password and the salt
         byte[] dk = pbkdf2(password.toCharArray(), passwordSalt, 1 << COST);
         byte[] hash = new byte[passwordSalt.length + dk.length];
         System.arraycopy(passwordSalt, 0, hash, 0, passwordSalt.length);
         System.arraycopy(dk, 0, hash, passwordSalt.length, dk.length);
         Base64.Encoder enc = Base64.getUrlEncoder().withoutPadding();
+
+        // Format the password hash
         passwordHash = ID + COST + '$' + enc.encodeToString(hash);
     }
 
+    /**
+     * Check a password against the password hash
+     * @param password the plain password to test
+     * @return true if the password match else false
+     */
     public boolean checkPassword(String password) {
+        // Check the password hash integrity
         Matcher m = LAYOUT.matcher(passwordHash);
         if (!m.matches())
             throw new IllegalArgumentException("Invalid token format");
+
+        // Gather hash data
         int iterations = iterations(Integer.parseInt(m.group(1)));
         byte[] hash = Base64.getUrlDecoder().decode(m.group(2));
         byte[] salt = Arrays.copyOfRange(hash, 0, SIZE / 8);
         byte[] check = pbkdf2(password.toCharArray(), salt, iterations);
+
+        // Check if the password match the hash
         int zero = 0;
         for (int idx = 0; idx < check.length; ++idx)
             zero |= hash[salt.length + idx] ^ check[idx];
+
         return zero == 0;
     }
 
+    /**
+     * Get the hash iteration
+     * @param cost the has cost
+     * @return the iterations
+     */
     private static int iterations(int cost) {
         if ((cost < 0) || (cost > 30))
             throw new IllegalArgumentException("cost: " + cost);
         return 1 << cost;
     }
 
+    /**
+     * Generate the password encryption
+     * @param password the plain password
+     * @param salt the salt
+     * @param iterations the hash iterations
+     * @return the password encoded hash
+     */
     private static byte[] pbkdf2(char[] password, byte[] salt, int iterations) {
         KeySpec spec = new PBEKeySpec(password, salt, iterations, SIZE);
         try {