diff --git a/src/api_data/conversation_api.rs b/src/api_data/conversation_api.rs
index c78a923..dcefe4e 100644
--- a/src/api_data/conversation_api.rs
+++ b/src/api_data/conversation_api.rs
@@ -40,12 +40,12 @@ impl ConversationAPI {
     pub fn new(conv: &Conversation) -> ConversationAPI {
         ConversationAPI {
             ID: conv.id,
-            ID_owner: conv.owner_id as u64,
+            ID_owner: conv.owner_id.id(),
             last_active: conv.last_active,
             name: ConvName(conv.name.clone()),
             following: LegacyBool(conv.following),
             saw_last_message: LegacyBool(conv.saw_last_message),
-            members: conv.members.iter().map(|x| x.clone() as u64).collect(),
+            members: conv.members.iter().map(|x| x.id()).collect(),
             canEveryoneAddMembers: conv.can_everyone_add_members,
 
             // TODO : update when call system is implemented
diff --git a/src/api_data/conversation_message_api.rs b/src/api_data/conversation_message_api.rs
index 72a73c9..055638b 100644
--- a/src/api_data/conversation_message_api.rs
+++ b/src/api_data/conversation_message_api.rs
@@ -26,7 +26,7 @@ impl ConversationMessageAPI {
         ConversationMessageAPI {
             ID: msg.id,
             convID: msg.conv_id,
-            ID_user: msg.user_id as u64,
+            ID_user: msg.user_id.id(),
             time_insert: msg.time_sent,
             message: msg.message.clone().unwrap_or(String::new()),
             image_path: msg.image_path.as_ref().map(|f| user_data_url(f)),
diff --git a/src/api_data/current_user_id.rs b/src/api_data/current_user_id.rs
index ca512a9..74614a8 100644
--- a/src/api_data/current_user_id.rs
+++ b/src/api_data/current_user_id.rs
@@ -6,13 +6,13 @@ use crate::data::user::UserID;
 #[derive(Serialize, Deserialize)]
 #[allow(non_snake_case)]
 pub struct CurrentUserID {
-    userID: i64
+    userID: u64
 }
 
 impl CurrentUserID {
-    pub fn new(id: UserID) -> CurrentUserID {
+    pub fn new(id: &UserID) -> CurrentUserID {
         CurrentUserID {
-            userID: id
+            userID: id.id()
         }
     }
 }
\ No newline at end of file
diff --git a/src/api_data/custom_emoji.rs b/src/api_data/custom_emoji.rs
index 0ad3702..1b4c687 100644
--- a/src/api_data/custom_emoji.rs
+++ b/src/api_data/custom_emoji.rs
@@ -2,6 +2,7 @@
 //!
 //! @author Pierre Hubert
 use serde::Serialize;
+
 use crate::data::custom_emoji::CustomEmoji;
 use crate::utils::user_data_utils::user_data_url;
 
@@ -9,21 +10,19 @@ use crate::utils::user_data_utils::user_data_url;
 #[allow(non_snake_case)]
 pub struct CustomEmojiAPI {
     id: u64,
-    userID: i64,
+    userID: u64,
     shortcut: String,
-    url: String
+    url: String,
 }
 
 impl CustomEmojiAPI {
-
     /// Create a new Custom Emoji API entry
     pub fn new(custom_emoji: &CustomEmoji) -> CustomEmojiAPI {
         CustomEmojiAPI {
             id: custom_emoji.id,
-            userID: custom_emoji.user_id,
+            userID: custom_emoji.user_id.id(),
             shortcut: custom_emoji.shortcut.to_string(),
             url: user_data_url(&custom_emoji.path),
         }
     }
-
 }
\ No newline at end of file
diff --git a/src/api_data/global_search_result_api.rs b/src/api_data/global_search_result_api.rs
index a92824b..d43982b 100644
--- a/src/api_data/global_search_result_api.rs
+++ b/src/api_data/global_search_result_api.rs
@@ -18,7 +18,7 @@ impl GlobalSearchResultAPI {
         match res {
             GlobalSearchResult::User(user_id) => GlobalSearchResultAPI {
                 kind: "user".to_string(),
-                id: user_id.clone() as u64,
+                id: user_id.id(),
             },
             GlobalSearchResult::Group(group_id) => GlobalSearchResultAPI {
                 kind: "group".to_string(),
diff --git a/src/api_data/list_unread_conversations_api.rs b/src/api_data/list_unread_conversations_api.rs
index 1f55dd3..78307d2 100644
--- a/src/api_data/list_unread_conversations_api.rs
+++ b/src/api_data/list_unread_conversations_api.rs
@@ -19,7 +19,7 @@ impl UnreadConversationAPI {
             id: conv.id,
             conv_name: conv.name.clone().unwrap_or(String::new()),
             last_active: conv.last_active,
-            userID: conv.user_id as u64,
+            userID: conv.user_id.id(),
             message: conv.message.clone()
         }
     }
diff --git a/src/api_data/res_find_user_by_virtual_directory.rs b/src/api_data/res_find_user_by_virtual_directory.rs
index 02cee19..935eca8 100644
--- a/src/api_data/res_find_user_by_virtual_directory.rs
+++ b/src/api_data/res_find_user_by_virtual_directory.rs
@@ -16,7 +16,7 @@ impl FindUserByVirtualDirectoryAPIResult {
     /// Construct a new `FindUserByVirtualDirectoryAPIResult` instance
     pub fn new(user_id: UserID) -> FindUserByVirtualDirectoryAPIResult {
         FindUserByVirtualDirectoryAPIResult {
-            userID: user_id as u64
+            userID: user_id.id()
         }
     }
 }
\ No newline at end of file
diff --git a/src/api_data/res_find_virtual_directory.rs b/src/api_data/res_find_virtual_directory.rs
index b578f8f..f43b683 100644
--- a/src/api_data/res_find_virtual_directory.rs
+++ b/src/api_data/res_find_virtual_directory.rs
@@ -19,7 +19,7 @@ impl ResultFindVirtualDirectory {
         match (user, group) {
 
             // User
-            (Ok(u), _) => ResultFindVirtualDirectory { kind: "user".to_string(), id: u.id as u64 },
+            (Ok(u), _) => ResultFindVirtualDirectory { kind: "user".to_string(), id: u.id.id() },
 
             // Group
             (_, Ok(g)) => ResultFindVirtualDirectory { kind: "group".to_string(), id: g.id() },
diff --git a/src/api_data/user_info.rs b/src/api_data/user_info.rs
index 2c38d15..942cffb 100644
--- a/src/api_data/user_info.rs
+++ b/src/api_data/user_info.rs
@@ -3,18 +3,18 @@
 //! @author Pierre Hubert
 use serde::Serialize;
 
-use crate::data::user::{User, UserPageStatus, UserID};
-use crate::helpers::{friends_helper, custom_emojies_helper, background_image_helper, likes_helper, user_helper};
-use crate::data::error::ResultBoxError;
-use crate::utils::user_data_utils::user_data_url;
-use crate::data::user::AccountImageVisibility::{EVERYONE, COMUNIC_USERS};
 use crate::api_data::custom_emoji::CustomEmojiAPI;
+use crate::data::error::ResultBoxError;
+use crate::data::user::{User, UserID, UserPageStatus};
+use crate::data::user::AccountImageVisibility::{COMUNIC_USERS, EVERYONE};
+use crate::helpers::{background_image_helper, custom_emojies_helper, friends_helper, likes_helper, user_helper};
 use crate::helpers::likes_helper::LikeType;
+use crate::utils::user_data_utils::user_data_url;
 
 #[derive(Serialize)]
 #[allow(non_snake_case)]
 pub struct APIUserInfo {
-    userID: i64,
+    userID: u64,
     firstName: String,
     lastName: String,
     publicPage: bool,
@@ -46,16 +46,16 @@ struct APIAdvancedInfo {
 impl APIUserInfo {
     /// Construct a new API user instance. Note: `user_id` is the ID of the user who makes the
     /// requests, not the user whose we return information about!
-    pub fn new(user_id: Option<UserID>, info: &User) -> ResultBoxError<APIUserInfo> {
+    pub fn new(user_id: &Option<UserID>, info: &User) -> ResultBoxError<APIUserInfo> {
         Ok(APIUserInfo {
-            userID: info.id,
+            userID: info.id.id(),
             firstName: info.first_name.to_string(),
             lastName: info.last_name.to_string(),
             publicPage: info.status != UserPageStatus::PRIVATE,
             openPage: info.status == UserPageStatus::OPEN,
             virtualDirectory: info.virtual_directory.clone().unwrap_or(String::new()),
             accountImage: APIUserInfo::get_account_image_url(user_id, info)?,
-            customEmojis: custom_emojies_helper::get_list_user(info.id)?
+            customEmojis: custom_emojies_helper::get_list_user(&info.id)?
                 .iter()
                 .map(|f| CustomEmojiAPI::new(f))
                 .collect(),
@@ -64,18 +64,18 @@ impl APIUserInfo {
     }
 
     /// Get advanced user information
-    pub fn new_advanced_info(user_id: Option<UserID>, info: &User) -> ResultBoxError<APIUserInfo> {
-        let mut user = APIUserInfo::new(user_id, info)?;
-        let curr_user_id = user_id.unwrap_or(0);
+    pub fn new_advanced_info(user_id: &Option<UserID>, info: &User) -> ResultBoxError<APIUserInfo> {
+        let mut user = APIUserInfo::new(&user_id, info)?;
+        let curr_user_id = user_id.clone().unwrap_or(UserID::new(0));
         let signed_in = user_id.is_some();
 
         // Check if we can return the number of friends of the user
         let number_friends = if info.public_friends_list || curr_user_id == info.id {
-            friends_helper::count_friends(info.id)?
+            friends_helper::count_friends(&info.id)?
         } else { 0 };
 
         let likes_page = if signed_in {
-            likes_helper::is_liking(curr_user_id, info.id as u64, LikeType::USER)?
+            likes_helper::is_liking(&curr_user_id, info.id.id(), LikeType::USER)?
         } else { false };
 
         // Set advanced user information
@@ -86,25 +86,25 @@ impl APIUserInfo {
             noCommentOnHisPage: info.block_comments_on_his_page,
             allowPostFromFriendOnHisPage: info.allow_posts_from_friends,
             account_creation_time: info.account_creation_time,
-            backgroundImage: background_image_helper::get_url(info.id),
+            backgroundImage: background_image_helper::get_url(&info.id),
             number_friends,
-            pageLikes: likes_helper::count(info.id as u64, LikeType::USER)?,
+            pageLikes: likes_helper::count(info.id.id(), LikeType::USER)?,
             user_page_like: likes_page,
-            can_post_texts: user_helper::can_create_posts(curr_user_id, info.id)?
+            can_post_texts: user_helper::can_create_posts(&curr_user_id, &info.id)?,
         });
 
         Ok(user)
     }
 
     /// Get the URL of a specific user account image
-    pub fn get_account_image_url(user_id: Option<UserID>, user: &User) -> ResultBoxError<String> {
+    pub fn get_account_image_url(user_id: &Option<UserID>, user: &User) -> ResultBoxError<String> {
         if !user.has_account_image() {
             return Ok(User::default_account_image_url());
         }
 
         let user_account_image = Ok(user_data_url(user.account_image_path.as_ref().unwrap()));
 
-        if user.account_image_visibility == EVERYONE || user_id == Some(user.id) {
+        if user.account_image_visibility == EVERYONE || user_id == &Some(user.id.clone()) {
             return user_account_image;
         }
 
@@ -113,7 +113,7 @@ impl APIUserInfo {
         }
 
         if user.account_image_visibility == COMUNIC_USERS ||
-            friends_helper::are_friend(user_id.unwrap(), user.id)? {
+            friends_helper::are_friend(&user_id.clone().unwrap(), &user.id)? {
             return user_account_image;
         }
 
diff --git a/src/controllers/account_controller.rs b/src/controllers/account_controller.rs
index a4bd650..dd9889f 100644
--- a/src/controllers/account_controller.rs
+++ b/src/controllers/account_controller.rs
@@ -34,7 +34,7 @@ pub fn login_user(request: &mut HttpRequestHandler) -> RequestResult {
 /// Sign out user
 pub fn logout_user(request: &mut HttpRequestHandler) -> RequestResult {
     account_helper::destroy_login_tokens(
-        request.user_id()?,
+        &request.user_id()?,
         request.api_client()
     )?;
 
@@ -43,5 +43,5 @@ pub fn logout_user(request: &mut HttpRequestHandler) -> RequestResult {
 
 /// Get current user ID
 pub fn user_id(request: &mut HttpRequestHandler) -> RequestResult {
-    request.set_response(CurrentUserID::new(request.user_id()?))
+    request.set_response(CurrentUserID::new(&request.user_id()?))
 }
\ No newline at end of file
diff --git a/src/controllers/conversations_controller.rs b/src/controllers/conversations_controller.rs
index 76c7523..555919a 100644
--- a/src/controllers/conversations_controller.rs
+++ b/src/controllers/conversations_controller.rs
@@ -15,13 +15,17 @@ use crate::controllers::routes::RequestResult;
 use crate::data::http_request_handler::HttpRequestHandler;
 use crate::data::new_conversation::NewConversation;
 use crate::data::new_conversation_message::NewConversationMessage;
+use crate::data::user::UserID;
 use crate::helpers::{conversations_helper, user_helper};
 use crate::utils::string_utils::remove_html_nodes;
 
 /// Create a new conversation
 pub fn create(r: &mut HttpRequestHandler) -> RequestResult {
     let name = r.post_string("name")?;
-    let mut members = r.post_numbers_list("users", 1)?;
+    let mut members = r.post_numbers_list("users", 1)?
+        .iter()
+        .map(|f| UserID::new(f.clone()))
+        .collect::<Vec<UserID>>();
 
     // Adapt name
     let name = match name.as_str() {
@@ -31,13 +35,13 @@ pub fn create(r: &mut HttpRequestHandler) -> RequestResult {
 
     // Check if members exists
     for user in &members {
-        if !user_helper::exists(user.clone())? {
-            r.not_found(format!("User {} not found!", user))?;
+        if !user_helper::exists(user)? {
+            r.not_found(format!("User {} not found!", user.id()))?;
         }
     }
 
     // Add current user ID if required
-    let curr_user_id = r.user_id()? as i64;
+    let curr_user_id = r.user_id()?;
     if !members.contains(&curr_user_id) {
         members.push(curr_user_id);
     }
@@ -57,7 +61,7 @@ pub fn create(r: &mut HttpRequestHandler) -> RequestResult {
 
 /// Get the list of conversations of a user
 pub fn get_list(r: &mut HttpRequestHandler) -> RequestResult {
-    let list = conversations_helper::get_list_user(r.user_id()?)?;
+    let list = conversations_helper::get_list_user(&r.user_id()?)?;
 
     r.set_response(list.iter().map(|c| ConversationAPI::new(c)).collect::<Vec<ConversationAPI>>())
 }
@@ -65,7 +69,7 @@ pub fn get_list(r: &mut HttpRequestHandler) -> RequestResult {
 /// Get information about a single conversation
 pub fn get_single(r: &mut HttpRequestHandler) -> RequestResult {
     let conversation_id = r.post_conv_id("conversationID")?;
-    let conv = conversations_helper::get_single(conversation_id, r.user_id()?)?;
+    let conv = conversations_helper::get_single(conversation_id, &r.user_id()?)?;
 
     r.set_response(ConversationAPI::new(&conv))
 }
@@ -73,12 +77,12 @@ pub fn get_single(r: &mut HttpRequestHandler) -> RequestResult {
 /// Update the settings of a conversation
 pub fn update_settings(r: &mut HttpRequestHandler) -> RequestResult {
     let conv_id = r.post_conv_id("conversationID")?;
-    let is_moderator = conversations_helper::is_user_moderator(r.user_id()?, conv_id)?;
+    let is_moderator = conversations_helper::is_user_moderator(&r.user_id()?, conv_id)?;
 
     // Update following state, if required
     if r.has_post_parameter("following") {
         conversations_helper::set_following(
-            r.user_id()?,
+            &r.user_id()?,
             conv_id,
             r.post_bool("following")?,
         )?;
@@ -86,7 +90,11 @@ pub fn update_settings(r: &mut HttpRequestHandler) -> RequestResult {
 
     // Update members list
     if r.has_post_parameter("members") {
-        let mut members = r.post_numbers_list("members", 1)?;
+        let mut members = r.post_numbers_list("members", 1)?
+            .iter()
+            .map(|f| UserID::new(f.clone()))
+            .collect::<Vec<UserID>>();
+
         let can_everyone_add_members = conversations_helper::can_everyone_add_members(conv_id)?;
 
         if !is_moderator && !can_everyone_add_members {
@@ -95,8 +103,8 @@ pub fn update_settings(r: &mut HttpRequestHandler) -> RequestResult {
 
         // Check if the members of the conversation really exists
         for member in &members {
-            if !user_helper::exists(member.clone())? {
-                r.not_found(format!("User {} not found!", member))?;
+            if !user_helper::exists(member)? {
+                r.not_found(format!("User {} not found!", member.id()))?;
             }
         }
 
@@ -142,7 +150,7 @@ pub fn find_private(r: &mut HttpRequestHandler) -> RequestResult {
     let allow_create = r.post_bool_opt("allowCreate", false);
 
     // Query the database
-    let mut list = conversations_helper::find_private(r.user_id()?, other_user)?;
+    let mut list = conversations_helper::find_private(&r.user_id()?, &other_user)?;
 
     if list.is_empty() {
         if !allow_create {
@@ -172,14 +180,14 @@ pub fn refresh_list(r: &mut HttpRequestHandler) -> RequestResult {
     // Check for new conversations
     if r.has_post_parameter("newConversations") {
         for conv_id in r.post_numbers_list("newConversations", 0)? {
-            if !conversations_helper::does_user_belongs_to(r.user_id()?, conv_id as u64)? {
+            if !conversations_helper::does_user_belongs_to(&r.user_id()?, conv_id)? {
                 r.forbidden(format!("Your do not belongs to conversation {} !", conv_id))?;
             }
 
-            let list_conv = conversations_helper::get_last_messages(conv_id as u64, 10)?;
+            let list_conv = conversations_helper::get_last_messages(conv_id , 10)?;
             list.insert(conv_id as u64, list_conv);
 
-            conversations_helper::mark_user_seen(conv_id as u64, r.user_id()?)?;
+            conversations_helper::mark_user_seen(conv_id as u64, &r.user_id()?)?;
         }
     }
 
@@ -202,14 +210,14 @@ pub fn refresh_list(r: &mut HttpRequestHandler) -> RequestResult {
             let last_message_id = v["last_message_id"].as_u64().unwrap_or(0);
 
             // Check user rights
-            if !conversations_helper::does_user_belongs_to(r.user_id()?, conv_id)? {
+            if !conversations_helper::does_user_belongs_to(&r.user_id()?, conv_id)? {
                 return r.forbidden(format!("You do not belong to conversation {}!", conv_id));
             }
 
             let list_conv = conversations_helper::get_new_messages(conv_id, last_message_id)?;
             list.insert(conv_id, list_conv);
 
-            conversations_helper::mark_user_seen(conv_id as u64, r.user_id()?)?;
+            conversations_helper::mark_user_seen(conv_id as u64, &r.user_id()?)?;
         }
     }
 
@@ -229,7 +237,7 @@ pub fn refresh_single(r: &mut HttpRequestHandler) -> RequestResult {
         _ => conversations_helper::get_new_messages(conv_id, last_message_id)?,
     };
 
-    conversations_helper::mark_user_seen(conv_id, r.user_id()?)?;
+    conversations_helper::mark_user_seen(conv_id, &r.user_id()?)?;
 
     r.set_response(ConversationMessageAPI::for_list(&messages))
 }
@@ -279,14 +287,14 @@ pub fn send_message(r: &mut HttpRequestHandler) -> RequestResult {
 
 /// Count the number of unread conversation of the user
 pub fn count_unread(r: &mut HttpRequestHandler) -> RequestResult {
-    let num = conversations_helper::count_unread_for_user(r.user_id()?)?;
+    let num = conversations_helper::count_unread_for_user(&r.user_id()?)?;
 
     r.set_response(ResultCountUnreadConversations::new(num))
 }
 
 /// Get the list of unread conversations of a user
 pub fn list_unread(r: &mut HttpRequestHandler) -> RequestResult {
-    let list = conversations_helper::get_list_unread(r.user_id()?)?;
+    let list = conversations_helper::get_list_unread(&r.user_id()?)?;
 
     r.set_response(UnreadConversationAPI::for_list(&list))
 }
@@ -295,7 +303,7 @@ pub fn list_unread(r: &mut HttpRequestHandler) -> RequestResult {
 pub fn delete_conversation(r: &mut HttpRequestHandler) -> RequestResult {
     let conv_id = r.post_conv_id("conversationID")?;
 
-    conversations_helper::remove_user_from_conversation(r.user_id()?, conv_id)?;
+    conversations_helper::remove_user_from_conversation(&r.user_id()?, conv_id)?;
 
     r.success("The conversation has been deleted")
 }
@@ -305,7 +313,7 @@ pub fn update_message(r: &mut HttpRequestHandler) -> RequestResult {
     let msg_id = r.post_u64("messageID")?;
     let new_content = r.post_string_opt("content", 3, true)?;
 
-    if !conversations_helper::is_message_owner(r.user_id()?, msg_id)? {
+    if !conversations_helper::is_message_owner(&r.user_id()?, msg_id)? {
         r.forbidden("You are not the owner of this message!".to_string())?;
     }
 
@@ -318,7 +326,7 @@ pub fn update_message(r: &mut HttpRequestHandler) -> RequestResult {
 pub fn delete_message(r: &mut HttpRequestHandler) -> RequestResult {
     let msg_id = r.post_u64("messageID")?;
 
-    if !conversations_helper::is_message_owner(r.user_id()?, msg_id)? {
+    if !conversations_helper::is_message_owner(&r.user_id()?, msg_id)? {
         r.forbidden("You are not the owner of this message!".to_string())?;
     }
 
diff --git a/src/controllers/search_controller.rs b/src/controllers/search_controller.rs
index a3648e9..3e44427 100644
--- a/src/controllers/search_controller.rs
+++ b/src/controllers/search_controller.rs
@@ -13,7 +13,10 @@ pub fn search_user(r: &mut HttpRequestHandler) -> RequestResult {
     let query = r.post_string_opt("query", 1, true)?;
     let limit = r.post_u64_opt("searchLimit", 5)?;
 
-    let list = user_helper::search_user(&query, limit)?;
+    let list = user_helper::search_user(&query, limit)?
+        .iter()
+        .map(|f| f.id())
+        .collect::<Vec<u64>>();
 
     r.set_response(list)
 }
diff --git a/src/controllers/user_controller.rs b/src/controllers/user_controller.rs
index 25bce28..5c8c7c4 100644
--- a/src/controllers/user_controller.rs
+++ b/src/controllers/user_controller.rs
@@ -15,8 +15,8 @@ use crate::helpers::user_helper::find_user_by_id;
 
 /// Get information about a single user
 pub fn get_single(request: &mut HttpRequestHandler) -> RequestResult {
-    let user_id = request.post_i64("userID")?;
-    let user = match user_helper::find_user_by_id(user_id) {
+    let user_id = UserID::new(request.post_u64("userID")?);
+    let user = match user_helper::find_user_by_id(&user_id) {
         Ok(user) => user,
         Err(e) => {
             println!("Error while getting user info: {}", e);
@@ -25,22 +25,23 @@ pub fn get_single(request: &mut HttpRequestHandler) -> RequestResult {
         }
     };
 
-    request.set_response(APIUserInfo::new(request.user_id_opt(), &user)?)
+    request.set_response(APIUserInfo::new(&request.user_id_opt(), &user)?)
 }
 
 /// Get information about several users
 pub fn get_multiple(request: &mut HttpRequestHandler) -> RequestResult {
     let user_ids = request.post_numbers_list("usersID", 1)?;
 
-    let mut map: HashMap<UserID, APIUserInfo> = HashMap::new();
+    let mut map: HashMap<u64, APIUserInfo> = HashMap::new();
 
     for user_id in user_ids {
+        let user_id = UserID::new(user_id);
         let user = request.ok_or_not_found(
-            find_user_by_id(user_id),
+            find_user_by_id(&user_id),
             "At least one user was not found!",
         )?;
 
-        map.insert(user_id, APIUserInfo::new(request.user_id_opt(), &user)?);
+        map.insert(user_id.id(), APIUserInfo::new(&request.user_id_opt(), &user)?);
     }
 
     request.set_response(map)
@@ -50,10 +51,10 @@ pub fn get_multiple(request: &mut HttpRequestHandler) -> RequestResult {
 pub fn get_advanced_info(request: &mut HttpRequestHandler) -> RequestResult {
     let user_id = request.post_user_id("userID")?;
 
-    if !user_helper::can_see_user_page(request.user_id_opt().unwrap_or(0), user_id)? {
+    if !user_helper::can_see_user_page(&request.user_id_opt().unwrap_or(UserID::new(0)), &user_id)? {
         request.forbidden("You are not allowed to see this user page!".to_string())?;
     }
 
-    let user = user_helper::find_user_by_id(user_id)?;
-    request.set_response(APIUserInfo::new_advanced_info(request.user_id_opt(), &user)?)
+    let user = user_helper::find_user_by_id(&user_id)?;
+    request.set_response(APIUserInfo::new_advanced_info(&request.user_id_opt(), &user)?)
 }
\ No newline at end of file
diff --git a/src/data/http_request_handler.rs b/src/data/http_request_handler.rs
index ea2241a..59f8aad 100644
--- a/src/data/http_request_handler.rs
+++ b/src/data/http_request_handler.rs
@@ -367,7 +367,7 @@ impl HttpRequestHandler {
 
     /// Get user ID. This function assess that a user ID is available to continue
     pub fn user_id(&self) -> ResultBoxError<UserID> {
-        match self.curr_user_id {
+        match self.curr_user_id.clone() {
             Some(s) => Ok(s),
             None => Err(ExecError::boxed_new("Could not get required user ID!"))
         }
@@ -375,7 +375,7 @@ impl HttpRequestHandler {
 
     /// Get a user ID, if available
     pub fn user_id_opt(&self) -> Option<UserID> {
-        self.curr_user_id
+        self.curr_user_id.clone()
     }
 
     /// Get an email included in the request
@@ -390,7 +390,7 @@ impl HttpRequestHandler {
     }
 
     /// Get a list of integers included in the request
-    pub fn post_numbers_list(&mut self, name: &str, min_len: usize) -> ResultBoxError<Vec<i64>> {
+    pub fn post_numbers_list(&mut self, name: &str, min_len: usize) -> ResultBoxError<Vec<u64>> {
         let param = self.post_string_opt(name, min_len, min_len != 0)?;
         let mut list = vec![];
 
@@ -399,7 +399,7 @@ impl HttpRequestHandler {
                 continue;
             }
 
-            list.push(split.parse::<i64>()?);
+            list.push(split.parse::<u64>()?);
         }
 
         if list.len() < min_len {
@@ -411,14 +411,14 @@ impl HttpRequestHandler {
 
     /// Get the ID of a user included in a POST request
     pub fn post_user_id(&mut self, name: &str) -> ResultBoxError<UserID> {
-        let user_id = self.post_i64(name)?;
+        let user_id = UserID::new(self.post_u64(name)?);
 
-        if user_id < 1 {
+        if user_id.id() < 1 {
             self.bad_request(format!("Invalid user specified in '{}'!", name))?;
         }
 
-        if !user_helper::exists(user_id)? {
-            self.not_found(format!("User with ID {} not found!", user_id))?;
+        if !user_helper::exists(&user_id)? {
+            self.not_found(format!("User with ID {} not found!", user_id.id()))?;
         }
 
         Ok(user_id)
@@ -444,7 +444,7 @@ impl HttpRequestHandler {
     pub fn post_conv_id(&mut self, name: &str) -> ResultBoxError<u64> {
         let conv_id = self.post_u64(name)?;
 
-        if !conversations_helper::does_user_belongs_to(self.user_id()?, conv_id)? {
+        if !conversations_helper::does_user_belongs_to(&self.user_id()?, conv_id)? {
             self.forbidden(format!("You do not belong to conversation {} !", conv_id))?;
         }
 
diff --git a/src/data/user.rs b/src/data/user.rs
index 9eba984..cebfadb 100644
--- a/src/data/user.rs
+++ b/src/data/user.rs
@@ -3,14 +3,31 @@ use crate::utils::user_data_utils::user_data_url;
 ///! User information
 ///!
 ///! @author Pierre Hubert
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct UserID(u64);
 
-pub type UserID = i64;
+impl UserID {
+    /// Initialize a new user ID object
+    pub fn new(id: u64) -> UserID {
+        UserID(id)
+    }
+
+    /// Get the current ID stored in this structure
+    pub fn id(&self) -> u64 {
+        self.0
+    }
+
+    /// Check if the ID currently stored in this structure is valid or not
+    pub fn is_valid(&self) -> bool {
+        self.0 > 0
+    }
+}
 
 #[derive(Debug, PartialEq)]
 pub enum UserPageStatus {
     OPEN,
     PUBLIC,
-    PRIVATE
+    PRIVATE,
 }
 
 #[derive(Debug, PartialEq)]
@@ -18,7 +35,7 @@ pub enum UserPageStatus {
 pub enum AccountImageVisibility {
     FRIENDS,
     COMUNIC_USERS,
-    EVERYONE
+    EVERYONE,
 }
 
 #[derive(Debug)]
@@ -41,7 +58,6 @@ pub struct User {
 }
 
 impl User {
-
     /// Get the URL pointing to the default account image
     pub fn default_account_image_url() -> String {
         user_data_url(crate::constants::DEFAULT_ACCOUNT_IMAGE)
diff --git a/src/helpers/account_helper.rs b/src/helpers/account_helper.rs
index 93b10b4..d91f54e 100644
--- a/src/helpers/account_helper.rs
+++ b/src/helpers/account_helper.rs
@@ -25,14 +25,14 @@ pub fn login_user(email: &str, password: &str, client: &APIClient) -> ResultBoxE
     }
 
     // Check if we already have a login token for this user
-    if let Ok(token) = get_client_tokens(user.id, client) {
+    if let Ok(token) = get_client_tokens(&user.id, client) {
         return Ok(token.token);
     }
 
 
     // Create new login tokens
     let new_token = UserAccessToken {
-        user_id: user.id,
+        user_id: user.id.clone(),
         client_id: client.id,
         token: rand_str(150),
     };
@@ -40,7 +40,7 @@ pub fn login_user(email: &str, password: &str, client: &APIClient) -> ResultBoxE
     // Save it
     database::insert(
         InsertQuery::new(USER_ACCESS_TOKENS_TABLE)
-            .add_i64("user_id", new_token.user_id)
+            .add_user_id("user_id", &new_token.user_id)
             .add_u32("service_id", client.id)
             .add_str("token1", &new_token.token)
             .add_str("token2", "dummy_data")
@@ -50,14 +50,14 @@ pub fn login_user(email: &str, password: &str, client: &APIClient) -> ResultBoxE
 }
 
 /// Get user login tokens
-fn get_client_tokens(user_id: UserID, client: &APIClient) -> ResultBoxError<UserAccessToken> {
+fn get_client_tokens(user_id: &UserID, client: &APIClient) -> ResultBoxError<UserAccessToken> {
     database::query_row(
         QueryInfo::new(USER_ACCESS_TOKENS_TABLE)
-            .cond_i64("user_id", user_id)
+            .cond_user_id("user_id", user_id)
             .cond_u32("service_id", client.id),
         |res| {
             Ok(UserAccessToken {
-                user_id: res.get_int64("user_id")?,
+                user_id: res.get_user_id("user_id")?,
                 client_id: res.get_int64("service_id")? as u32,
                 token: res.get_str("token1")?,
             })
@@ -72,16 +72,16 @@ pub fn get_user_by_login_token(token: &str, client: &APIClient) -> ResultBoxErro
             .cond_u32("service_id", client.id)
             .cond("token1", token)
             .add_field("user_id"),
-        |res| res.get_int64("user_id"),
+        |res| res.get_user_id("user_id"),
     )
 }
 
 /// Destroy a given user login tokens
-pub fn destroy_login_tokens(id: UserID, client: &APIClient) -> ResultBoxError<()> {
+pub fn destroy_login_tokens(id: &UserID, client: &APIClient) -> ResultBoxError<()> {
 
     database::delete(DeleteQuery::new(USER_ACCESS_TOKENS_TABLE)
         .cond_u32("service_id", client.id)
-        .cond_i64("user_id", id)
+        .cond_user_id("user_id", id)
     )?;
 
     Ok(())
diff --git a/src/helpers/background_image_helper.rs b/src/helpers/background_image_helper.rs
index add71f6..fc956a6 100644
--- a/src/helpers/background_image_helper.rs
+++ b/src/helpers/background_image_helper.rs
@@ -6,6 +6,6 @@
 use crate::data::user::UserID;
 use crate::utils::user_data_utils::user_data_url;
 
-pub fn get_url(_user_id: UserID) -> String {
+pub fn get_url(_user_id: &UserID) -> String {
     user_data_url("imgfond/0.jpg")
 }
\ No newline at end of file
diff --git a/src/helpers/conversations_helper.rs b/src/helpers/conversations_helper.rs
index 71c8949..b30a5ca 100644
--- a/src/helpers/conversations_helper.rs
+++ b/src/helpers/conversations_helper.rs
@@ -19,7 +19,7 @@ use crate::utils::user_data_utils::user_data_path;
 pub fn create(conv: &NewConversation) -> ResultBoxError<u64> {
     // Create the conversation in the main table
     let conv_id = InsertQuery::new(CONV_LIST_TABLE)
-        .add_user_id("user_id", conv.owner_id)
+        .add_user_id("user_id", &conv.owner_id)
         .add_str("name", conv.name.clone().unwrap_or(String::new()).as_str())
         .add_u64("last_active", time())
         .add_u64("creation_time", time())
@@ -34,14 +34,14 @@ pub fn create(conv: &NewConversation) -> ResultBoxError<u64> {
             follow = conv.owner_following;
         }
 
-        add_member(conv_id, member.clone(), follow)?;
+        add_member(conv_id, member, follow)?;
     }
 
     Ok(conv_id)
 }
 
 /// Add a member to a conversation
-pub fn add_member(conv_id: u64, user_id: UserID, following: bool) -> ResultBoxError<()> {
+pub fn add_member(conv_id: u64, user_id: &UserID, following: bool) -> ResultBoxError<()> {
     InsertQuery::new(CONV_USERS_TABLE)
         .add_u64("conv_id", conv_id)
         .add_user_id("user_id", user_id)
@@ -54,7 +54,7 @@ pub fn add_member(conv_id: u64, user_id: UserID, following: bool) -> ResultBoxEr
 }
 
 /// Remove a member from a conversation
-pub fn remove_member(conv_id: u64, user_id: UserID) -> ResultBoxError<()> {
+pub fn remove_member(conv_id: u64, user_id: &UserID) -> ResultBoxError<()> {
     database::DeleteQuery::new(CONV_USERS_TABLE)
         .cond_u64("conv_id", conv_id)
         .cond_user_id("user_id", user_id)
@@ -62,7 +62,7 @@ pub fn remove_member(conv_id: u64, user_id: UserID) -> ResultBoxError<()> {
 }
 
 /// Get the list of conversations of a specific user
-pub fn get_list_user(user_id: UserID) -> ResultBoxError<Vec<Conversation>> {
+pub fn get_list_user(user_id: &UserID) -> ResultBoxError<Vec<Conversation>> {
     database::QueryInfo::new(CONV_LIST_TABLE)
         .alias("l")
 
@@ -85,7 +85,7 @@ pub fn get_list_user(user_id: UserID) -> ResultBoxError<Vec<Conversation>> {
 }
 
 /// Get information about a single conversation
-pub fn get_single(conv_id: u64, user_id: UserID) -> ResultBoxError<Conversation> {
+pub fn get_single(conv_id: u64, user_id: &UserID) -> ResultBoxError<Conversation> {
     // Tables
     database::QueryInfo::new(CONV_LIST_TABLE)
         .alias("l")
@@ -112,7 +112,7 @@ pub fn get_list_members(conv_id: u64) -> ResultBoxError<Vec<UserID>> {
 }
 
 /// Check if a user belongs to a conversation or not
-pub fn does_user_belongs_to(user_id: UserID, conv_id: u64) -> ResultBoxError<bool> {
+pub fn does_user_belongs_to(user_id: &UserID, conv_id: u64) -> ResultBoxError<bool> {
     Ok(database::QueryInfo::new(CONV_USERS_TABLE)
         .cond_u64("conv_id", conv_id)
         .cond_user_id("user_id", user_id)
@@ -120,7 +120,7 @@ pub fn does_user_belongs_to(user_id: UserID, conv_id: u64) -> ResultBoxError<boo
 }
 
 /// Check out wheter a user is the moderator of a conversation or not
-pub fn is_user_moderator(user_id: UserID, conv_id: u64) -> ResultBoxError<bool> {
+pub fn is_user_moderator(user_id: &UserID, conv_id: u64) -> ResultBoxError<bool> {
     Ok(database::QueryInfo::new(CONV_LIST_TABLE)
         .cond_u64("id", conv_id)
         .cond_user_id("user_id", user_id)
@@ -136,7 +136,7 @@ pub fn can_everyone_add_members(conv_id: u64) -> ResultBoxError<bool> {
 }
 
 /// Set whether a user is following a conversation or not
-pub fn set_following(user_id: UserID, conv_id: u64, following: bool) -> ResultBoxError<()> {
+pub fn set_following(user_id: &UserID, conv_id: u64, following: bool) -> ResultBoxError<()> {
     database::UpdateInfo::new(CONV_USERS_TABLE)
         .cond_u64("conv_id", conv_id)
         .cond_user_id("user_id", user_id)
@@ -154,7 +154,7 @@ pub fn set_members(conv_id: u64, new_list: &Vec<UserID>, can_delete: bool) -> Re
             continue;
         }
 
-        add_member(conv_id, member.clone(), true)?;
+        add_member(conv_id, member, true)?;
     }
 
     // Remove a member
@@ -163,7 +163,7 @@ pub fn set_members(conv_id: u64, new_list: &Vec<UserID>, can_delete: bool) -> Re
             if new_list.contains(&member) {
                 continue;
             }
-            remove_member(conv_id, member)?;
+            remove_member(conv_id, &member)?;
         }
     }
 
@@ -188,7 +188,7 @@ pub fn set_can_everyone_add_members(conv_id: u64, allow: bool) -> ResultBoxError
 }
 
 /// Search for private conversation between two users
-pub fn find_private(user_1: UserID, user_2: UserID) -> ResultBoxError<Vec<u64>> {
+pub fn find_private(user_1: &UserID, user_2: &UserID) -> ResultBoxError<Vec<u64>> {
     database::QueryInfo::new(CONV_USERS_TABLE)
         .alias("t1")
 
@@ -246,7 +246,7 @@ pub fn get_older_messages(conv_id: u64, start_id: u64, limit: u64) -> ResultBoxE
 }
 
 /// Get all the messages of a single user for a conversation
-pub fn get_user_messages_for_conversations(conv_id: u64, user_id: UserID) -> ResultBoxError<Vec<ConversationMessage>> {
+pub fn get_user_messages_for_conversations(conv_id: u64, user_id: &UserID) -> ResultBoxError<Vec<ConversationMessage>> {
     database::QueryInfo::new(CONV_MESSAGES_TABLE)
         .cond_u64("conv_id", conv_id)
         .cond_user_id("user_id", user_id)
@@ -274,7 +274,7 @@ pub fn send_message(msg: &NewConversationMessage) -> ResultBoxError<()> {
     // Insert the message in the database
     database::InsertQuery::new(CONV_MESSAGES_TABLE)
         .add_u64("conv_id", msg.conv_id)
-        .add_user_id("user_id", msg.user_id)
+        .add_user_id("user_id", &msg.user_id)
         .add_u64("time_insert", t)
         .add_str("message", msg.message.as_str())
         .add_opt_str("image_path", msg.image_path.as_ref())
@@ -292,7 +292,7 @@ pub fn send_message(msg: &NewConversationMessage) -> ResultBoxError<()> {
         .cond_legacy_bool("saw_last_message", true)
 
         .custom_where("user_id != ?")
-        .add_custom_where_arg_u64(msg.user_id as u64)
+        .add_custom_where_arg_u64(msg.user_id.id())
 
         .set_legacy_bool("saw_last_message", false)
         .exec()?;
@@ -332,7 +332,7 @@ pub fn delete_message_by_id(id: u64) -> ResultBoxError<()> {
 }
 
 /// Count the number of unread conversation for a specified user
-pub fn count_unread_for_user(user_id: UserID) -> ResultBoxError<usize> {
+pub fn count_unread_for_user(user_id: &UserID) -> ResultBoxError<usize> {
     database::QueryInfo::new(CONV_USERS_TABLE)
         .cond_user_id("user_id", user_id)
         .cond_legacy_bool("saw_last_message", false)
@@ -341,7 +341,7 @@ pub fn count_unread_for_user(user_id: UserID) -> ResultBoxError<usize> {
 }
 
 /// Get the list of unread conversations of a user
-pub fn get_list_unread(user_id: UserID) -> ResultBoxError<Vec<UnreadConversation>> {
+pub fn get_list_unread(user_id: &UserID) -> ResultBoxError<Vec<UnreadConversation>> {
     database::QueryInfo::new(CONV_USERS_TABLE)
         .alias("users")
         .join(CONV_LIST_TABLE, "list", "users.conv_id = list.id")
@@ -364,7 +364,7 @@ pub fn get_list_unread(user_id: UserID) -> ResultBoxError<Vec<UnreadConversation
 }
 
 /// Indicate that a user has seen the last messages of a conversation
-pub fn mark_user_seen(conv_id: u64, user_id: UserID) -> ResultBoxError<()> {
+pub fn mark_user_seen(conv_id: u64, user_id: &UserID) -> ResultBoxError<()> {
     database::UpdateInfo::new(CONV_USERS_TABLE)
         .cond_u64("conv_id", conv_id)
         .cond_user_id("user_id", user_id)
@@ -374,7 +374,7 @@ pub fn mark_user_seen(conv_id: u64, user_id: UserID) -> ResultBoxError<()> {
 }
 
 /// Remove a user from a conversation
-pub fn remove_user_from_conversation(user_id: UserID, conv_id: u64) -> ResultBoxError<()> {
+pub fn remove_user_from_conversation(user_id: &UserID, conv_id: u64) -> ResultBoxError<()> {
     if is_user_moderator(user_id, conv_id)? {
         delete_conversation(conv_id)
     } else {
@@ -403,7 +403,7 @@ pub fn delete_conversation(conv_id: u64) -> ResultBoxError<()> {
 }
 
 /// Delete a conversation membership
-pub fn delete_member(user_id: UserID, conv_id: u64) -> ResultBoxError<()> {
+pub fn delete_member(user_id: &UserID, conv_id: u64) -> ResultBoxError<()> {
     for msg in get_user_messages_for_conversations(conv_id, user_id)? {
         delete_message(&msg)?;
     }
@@ -415,7 +415,7 @@ pub fn delete_member(user_id: UserID, conv_id: u64) -> ResultBoxError<()> {
 }
 
 /// Check out whether a user is the owner of a message or not
-pub fn is_message_owner(user_id: UserID, message_id: u64) -> ResultBoxError<bool> {
+pub fn is_message_owner(user_id: &UserID, message_id: u64) -> ResultBoxError<bool> {
     database::QueryInfo::new(CONV_MESSAGES_TABLE)
         .cond_u64("id", message_id)
         .cond_user_id("user_id", user_id)
diff --git a/src/helpers/custom_emojies_helper.rs b/src/helpers/custom_emojies_helper.rs
index 527f251..ca6d777 100644
--- a/src/helpers/custom_emojies_helper.rs
+++ b/src/helpers/custom_emojies_helper.rs
@@ -9,9 +9,9 @@ use crate::helpers::database;
 use crate::constants::database_tables_names::EMOJIS_TABLE;
 
 /// Get the list of emojies of a user
-pub fn get_list_user(user_id: UserID) -> ResultBoxError<Vec<CustomEmoji>> {
+pub fn get_list_user(user_id: &UserID) -> ResultBoxError<Vec<CustomEmoji>> {
     database::QueryInfo::new(EMOJIS_TABLE)
-        .cond_i64("user_id", user_id)
+        .cond_user_id("user_id", user_id)
         .exec(db_to_custom_emoji)
 }
 
@@ -19,7 +19,7 @@ pub fn get_list_user(user_id: UserID) -> ResultBoxError<Vec<CustomEmoji>> {
 fn db_to_custom_emoji(row: &database::RowResult) -> ResultBoxError<CustomEmoji> {
     Ok(CustomEmoji {
         id: row.get_u64("id")?,
-        user_id: row.get_int64("user_id")?,
+        user_id: row.get_user_id("user_id")?,
         shortcut: row.get_str("shortcut")?,
         path: row.get_str("path")?
     })
diff --git a/src/helpers/database.rs b/src/helpers/database.rs
index 88fdf11..382e4b2 100644
--- a/src/helpers/database.rs
+++ b/src/helpers/database.rs
@@ -138,8 +138,8 @@ impl QueryInfo {
         self
     }
 
-    pub fn cond_user_id(mut self, key: &str, val: UserID) -> QueryInfo {
-        self.conditions.insert(key.to_string(), val.to_string());
+    pub fn cond_user_id(mut self, key: &str, val: &UserID) -> QueryInfo {
+        self.conditions.insert(key.to_string(), val.id().to_string());
         self
     }
 
@@ -290,7 +290,7 @@ impl<'a> RowResult<'a> {
 
     /// Get the ID of a user included in the request
     pub fn get_user_id(&self, name: &str) -> ResultBoxError<UserID> {
-        self.get_int64(name)
+        Ok(UserID::new(self.get_u64(name)?))
     }
 
     /// Get the ID of a group included in the response
@@ -514,8 +514,8 @@ impl InsertQuery {
         self
     }
 
-    pub fn add_user_id(mut self, key: &str, value: UserID) -> InsertQuery {
-        self.values.insert(key.to_string(), Value::from(value));
+    pub fn add_user_id(mut self, key: &str, value: &UserID) -> InsertQuery {
+        self.values.insert(key.to_string(), Value::from(value.id()));
         self
     }
 
@@ -611,8 +611,8 @@ impl DeleteQuery {
         self
     }
 
-    pub fn cond_user_id(mut self, key: &str, value: UserID) -> DeleteQuery {
-        self.conditions.insert(key.to_string(), Value::from(value));
+    pub fn cond_user_id(mut self, key: &str, value: &UserID) -> DeleteQuery {
+        self.conditions.insert(key.to_string(), Value::from(value.id()));
         self
     }
 
@@ -666,8 +666,8 @@ impl UpdateInfo {
     }
 
     /// Filter with a user id
-    pub fn cond_user_id(mut self, name: &str, val: UserID) -> UpdateInfo {
-        self.cond.insert(name.to_string(), Value::Int(val));
+    pub fn cond_user_id(mut self, name: &str, val: &UserID) -> UpdateInfo {
+        self.cond.insert(name.to_string(), Value::UInt(val.id()));
         self
     }
 
diff --git a/src/helpers/friends_helper.rs b/src/helpers/friends_helper.rs
index c4362c5..cd436e3 100644
--- a/src/helpers/friends_helper.rs
+++ b/src/helpers/friends_helper.rs
@@ -10,23 +10,23 @@ use crate::constants::database_tables_names::FRIENDS_TABLE;
 use crate::helpers::database::QueryInfo;
 
 /// Check out whether two users are friend or not
-pub fn are_friend(user_one: UserID, user_two: UserID) -> ResultBoxError<bool> {
+pub fn are_friend(user_one: &UserID, user_two: &UserID) -> ResultBoxError<bool> {
     Ok(database::count(QueryInfo::new(FRIENDS_TABLE)
-        .cond_i64("ID_personne", user_one)
-        .cond_i64("ID_amis", user_two)
+        .cond_user_id("ID_personne", user_one)
+        .cond_user_id("ID_amis", user_two)
         .cond_i64("actif", 1))? > 0)
 }
 
 /// Count the number of friends of a user
-pub fn count_friends(user_id: UserID) -> ResultBoxError<usize> {
+pub fn count_friends(user_id: &UserID) -> ResultBoxError<usize> {
     QueryInfo::new(FRIENDS_TABLE)
-        .cond_i64("ID_amis", user_id)
+        .cond_user_id("ID_amis", user_id)
         .cond_u32("actif", 1)
         .exec_count()
 }
 
 /// Check if a user can create posts on another friend's page
-pub fn can_post_texts(user_id: UserID, target_user: UserID) -> ResultBoxError<bool> {
+pub fn can_post_texts(user_id: &UserID, target_user: &UserID) -> ResultBoxError<bool> {
     QueryInfo::new(FRIENDS_TABLE)
         .cond_user_id("ID_personne", target_user)
         .cond_user_id("ID_amis", user_id)
diff --git a/src/helpers/groups_helper.rs b/src/helpers/groups_helper.rs
index 47c0ce0..b588c0e 100644
--- a/src/helpers/groups_helper.rs
+++ b/src/helpers/groups_helper.rs
@@ -97,7 +97,7 @@ pub fn create(group: &NewGroup) -> ResultBoxError<GroupID> {
     // First, create the group
     let group_id = database::InsertQuery::new(GROUPS_LIST_TABLE)
         .add_u64("time_create", time())
-        .add_user_id("userid_create", group.owner_id)
+        .add_user_id("userid_create", &group.owner_id)
         .add_str("name", &group.name)
         .insert()?.ok_or(ExecError::new("Could not get group ID!"))?;
     let group_id = GroupID::new(group_id);
@@ -105,7 +105,7 @@ pub fn create(group: &NewGroup) -> ResultBoxError<GroupID> {
     // Insert first member
     insert_member(&GroupMember {
         id: 0,
-        user_id: group.owner_id,
+        user_id: group.owner_id.clone(),
         group_id: group_id.clone(),
         time_create: time(),
         level: GroupMembershipLevel::ADMINISTRATOR,
@@ -119,7 +119,7 @@ pub fn create(group: &NewGroup) -> ResultBoxError<GroupID> {
 pub fn insert_member(m: &GroupMember) -> ResultBoxError<()> {
     database::InsertQuery::new(GROUPS_MEMBERS_TABLE)
         .add_group_id("groups_id", &m.group_id)
-        .add_user_id("user_id", m.user_id)
+        .add_user_id("user_id", &m.user_id)
         .add_u64("time_create", m.time_create)
         .add_u32("level", m.level.to_db())
         .insert_drop_result()
@@ -129,7 +129,7 @@ pub fn insert_member(m: &GroupMember) -> ResultBoxError<()> {
 pub fn get_list_user(user_id: UserID, only_followed: bool) -> ResultBoxError<Vec<GroupID>> {
     let mut query = database::QueryInfo::new(GROUPS_MEMBERS_TABLE)
         .add_field("groups_id")
-        .cond_user_id("user_id", user_id);
+        .cond_user_id("user_id", &user_id);
 
     if only_followed {
         query = query.cond_legacy_bool("following", true);
@@ -176,7 +176,7 @@ pub fn search_group(query: &str, limit: u64) -> ResultBoxError<Vec<GroupID>> {
 pub fn get_membership(group_id: &GroupID, user_id: Option<UserID>) -> ResultBoxError<GroupMember> {
     let default_membership = GroupMember {
         id: 0,
-        user_id: 0,
+        user_id: UserID::new(0),
         group_id: group_id.clone(),
         time_create: 0,
         level: GroupMembershipLevel::VISITOR,
@@ -191,7 +191,7 @@ pub fn get_membership(group_id: &GroupID, user_id: Option<UserID>) -> ResultBoxE
 
     Ok(database::QueryInfo::new(GROUPS_MEMBERS_TABLE)
         .cond_group_id("groups_id", group_id)
-        .cond_user_id("user_id", user_id)
+        .cond_user_id("user_id", &user_id)
         .query_row(db_to_group_member)
         .unwrap_or(default_membership))
 }
@@ -203,7 +203,7 @@ pub fn get_membership_level(group_id: &GroupID, user_id: Option<UserID>) -> Resu
         Some(user_id) => {
             let level = database::QueryInfo::new(GROUPS_MEMBERS_TABLE)
                 .cond_group_id("groups_id", group_id)
-                .cond_user_id("user_id", user_id)
+                .cond_user_id("user_id", &user_id)
                 .add_field("level")
                 .query_row(|f| f.get_u32("level"))
                 .unwrap_or(GroupMembershipLevel::VISITOR.to_db());
diff --git a/src/helpers/likes_helper.rs b/src/helpers/likes_helper.rs
index f968a9e..0e95885 100644
--- a/src/helpers/likes_helper.rs
+++ b/src/helpers/likes_helper.rs
@@ -36,14 +36,14 @@ pub fn count(id: u64, kind: LikeType) -> ResultBoxError<usize> {
 }
 
 /// Check if a user likes an element or not
-pub fn is_liking(user_id: UserID, id: u64, kind: LikeType) -> ResultBoxError<bool> {
-    if user_id == 0 {
+pub fn is_liking(user_id: &UserID, id: u64, kind: LikeType) -> ResultBoxError<bool> {
+    if !user_id.is_valid() {
         return Ok(false);
     }
 
     Ok(QueryInfo::new(LIKES_TABLE)
         .cond_u64("ID_type", id)
-        .cond_i64("ID_personne", user_id)
+        .cond_user_id("ID_personne", user_id)
         .cond("type", kind.to_db_type().as_ref())
         .exec_count()? > 0)
 }
\ No newline at end of file
diff --git a/src/helpers/user_helper.rs b/src/helpers/user_helper.rs
index 2761449..d861ca0 100644
--- a/src/helpers/user_helper.rs
+++ b/src/helpers/user_helper.rs
@@ -10,9 +10,9 @@ use crate::helpers::friends_helper::are_friend;
 /// @author Pierre Hubert
 
 /// Get & return information about a user based on its ID
-pub fn find_user_by_id(id: UserID) -> ResultBoxError<User> {
+pub fn find_user_by_id(id: &UserID) -> ResultBoxError<User> {
     exec_get_user_query(
-        database::QueryInfo::new(USERS_TABLE).cond_i64("ID", id))
+        database::QueryInfo::new(USERS_TABLE).cond_user_id("ID", id))
 }
 
 /// Get & return information about a user based on his email
@@ -49,7 +49,7 @@ fn exec_get_user_query(query: database::QueryInfo) -> ResultBoxError<User> {
         };
 
         Ok(User {
-            id: res.get_int64("ID")?,
+            id: res.get_user_id("ID")?,
             email: res.get_str("mail")?,
             password: res.get_str("password")?,
             first_name: res.get_str("prenom")?,
@@ -69,14 +69,14 @@ fn exec_get_user_query(query: database::QueryInfo) -> ResultBoxError<User> {
 }
 
 /// Check out whether a given id maps to a user or not
-pub fn exists(id: UserID) -> ResultBoxError<bool> {
+pub fn exists(id: &UserID) -> ResultBoxError<bool> {
     Ok(database::QueryInfo::new(USERS_TABLE)
-        .cond_i64("ID", id)
+        .cond_user_id("ID", id)
         .exec_count()? > 0)
 }
 
 /// Check if a given user can see another user's page
-pub fn can_see_user_page(user_id: UserID, target_user: UserID) -> ResultBoxError<bool> {
+pub fn can_see_user_page(user_id: &UserID, target_user: &UserID) -> ResultBoxError<bool> {
     if user_id == target_user {
         return Ok(true);
     }
@@ -89,7 +89,7 @@ pub fn can_see_user_page(user_id: UserID, target_user: UserID) -> ResultBoxError
     }
 
     // The user need to be signed in
-    if user_id <= 0 {
+    if user_id.id() <= 0 {
         return Ok(false);
     }
 
@@ -107,15 +107,15 @@ pub fn can_see_user_page(user_id: UserID, target_user: UserID) -> ResultBoxError
 }
 
 /// Check out whether a user allow posts on his page or not
-pub fn allow_posts_on_his_page(user_id: UserID) -> ResultBoxError<bool> {
+pub fn allow_posts_on_his_page(user_id: &UserID) -> ResultBoxError<bool> {
     Ok(find_user_by_id(user_id)?.allow_posts_from_friends)
 }
 
 /// Check out if a user can create posts on another user page
-pub fn can_create_posts(user_id: UserID, target_id: UserID) -> ResultBoxError<bool> {
+pub fn can_create_posts(user_id: &UserID, target_id: &UserID) -> ResultBoxError<bool> {
 
     // Login required
-    if user_id <= 0 {
+    if !user_id.is_valid() {
         return Ok(false);
     }
 
diff --git a/src/utils/user_data_utils.rs b/src/utils/user_data_utils.rs
index ee5d448..ceda793 100644
--- a/src/utils/user_data_utils.rs
+++ b/src/utils/user_data_utils.rs
@@ -28,7 +28,7 @@ pub fn user_data_path(uri: &Path) -> PathBuf {
 /// This function returns the relative folder path in user data directory where the file can be
 /// created
 pub fn prepare_file_creation(user_id: UserID, folder: &str) -> ResultBoxError<PathBuf> {
-    let subfolder = match user_id {
+    let subfolder = match user_id.id() {
         0 => Path::new(folder).to_path_buf(),
         id => Path::new(folder).join(to_string(&id)?)
     };