diff --git a/back/package.json b/back/package.json
index 9f698575..a20c876f 100644
--- a/back/package.json
+++ b/back/package.json
@@ -16,7 +16,8 @@
     "type": "git",
     "url": "git+https://github.com/thecodingmachine/workadventure.git"
   },
-  "contributors": [{
+  "contributors": [
+    {
       "name": "Grégoire Parant",
       "email": "g.parant@thecodingmachine.com"
     },
@@ -27,7 +28,8 @@
     {
       "name": "Arthmaël Poly",
       "email": "a.poly@thecodingmachine.com"
-    }],
+    }
+  ],
   "license": "SEE LICENSE IN LICENSE.txt",
   "bugs": {
     "url": "https://github.com/thecodingmachine/workadventure/issues"
@@ -41,6 +43,7 @@
     "@types/uuidv4": "^5.0.0",
     "body-parser": "^1.19.0",
     "express": "^4.17.1",
+    "generic-type-guard": "^3.2.0",
     "http-status-codes": "^1.4.0",
     "jsonwebtoken": "^8.5.1",
     "prom-client": "^12.0.0",
diff --git a/back/src/Controller/AuthenticateController.ts b/back/src/Controller/AuthenticateController.ts
index 45e195fc..71e538a4 100644
--- a/back/src/Controller/AuthenticateController.ts
+++ b/back/src/Controller/AuthenticateController.ts
@@ -4,6 +4,11 @@ import {BAD_REQUEST, OK} from "http-status-codes";
 import {SECRET_KEY, URL_ROOM_STARTED} from "../Enum/EnvironmentVariable"; //TODO fix import by "_Enum/..."
 import { uuid } from 'uuidv4';
 
+export interface TokenInterface {
+    name: string,
+    userId: string
+}
+
 export class AuthenticateController {
     App : Application;
 
@@ -24,7 +29,7 @@ export class AuthenticateController {
             }*/
             //TODO check user email for The Coding Machine game
             const userId = uuid();
-            const token = Jwt.sign({name: param.name, userId: userId}, SECRET_KEY, {expiresIn: '24h'});
+            const token = Jwt.sign({name: param.name, userId: userId} as TokenInterface, SECRET_KEY, {expiresIn: '24h'});
             return res.status(OK).send({
                 token: token,
                 mapUrlStart: URL_ROOM_STARTED,
diff --git a/back/src/Controller/IoSocketController.ts b/back/src/Controller/IoSocketController.ts
index 646464e1..78efe558 100644
--- a/back/src/Controller/IoSocketController.ts
+++ b/back/src/Controller/IoSocketController.ts
@@ -8,12 +8,17 @@ import {SECRET_KEY, MINIMUM_DISTANCE, GROUP_RADIUS} from "../Enum/EnvironmentVar
 import {World} from "../Model/World";
 import {Group} from "_Model/Group";
 import {UserInterface} from "_Model/UserInterface";
-import {SetPlayerDetailsMessage} from "_Model/Websocket/SetPlayerDetailsMessage";
+import {isSetPlayerDetailsMessage,} from "../Model/Websocket/SetPlayerDetailsMessage";
 import {MessageUserJoined} from "../Model/Websocket/MessageUserJoined";
 import {MessageUserMoved} from "../Model/Websocket/MessageUserMoved";
 import si from "systeminformation";
 import {Gauge} from "prom-client";
 import os from 'os';
+import {TokenInterface} from "../Controller/AuthenticateController";
+import {isJoinRoomMessageInterface} from "../Model/Websocket/JoinRoomMessage";
+import {isPointInterface, PointInterface} from "../Model/Websocket/PointInterface";
+import {isWebRtcSignalMessageInterface} from "../Model/Websocket/WebRtcSignalMessage";
+import {UserInGroupInterface} from "../Model/Websocket/UserInGroupInterface";
 
 enum SockerIoEvent {
     CONNECTION = "connection",
@@ -23,7 +28,6 @@ enum SockerIoEvent {
     USER_MOVED = "user-moved", // From server to client
     USER_LEFT = "user-left", // From server to client
     WEBRTC_SIGNAL = "webrtc-signal",
-    WEBRTC_OFFER = "webrtc-offer",
     WEBRTC_START = "webrtc-start",
     WEBRTC_DISCONNECT = "webrtc-disconect",
     MESSAGE_ERROR = "message-error",
@@ -61,10 +65,15 @@ export class IoSocketController {
             if(this.searchClientByToken(socket.handshake.query.token)){
                 return next(new Error('Authentication error'));
             }
-            Jwt.verify(socket.handshake.query.token, SECRET_KEY, (err: JsonWebTokenError, tokenDecoded: any) => {
+            Jwt.verify(socket.handshake.query.token, SECRET_KEY, (err: JsonWebTokenError, tokenDecoded: object) => {
                 if (err) {
                     return next(new Error('Authentication error'));
                 }
+
+                if (!this.isValidToken(tokenDecoded)) {
+                    return next(new Error('Authentication error, invalid token structure'));
+                }
+
                 (socket as ExSocketInterface).token = tokenDecoded;
                 (socket as ExSocketInterface).userId = tokenDecoded.userId;
                 next();
@@ -74,14 +83,24 @@ export class IoSocketController {
         this.ioConnection();
     }
 
+    private isValidToken(token: object): token is TokenInterface {
+        if (typeof((token as TokenInterface).userId) !== 'string') {
+            return false;
+        }
+        if (typeof((token as TokenInterface).name) !== 'string') {
+            return false;
+        }
+        return true;
+    }
+
     /**
      *
      * @param token
      */
     searchClientByToken(token: string): ExSocketInterface | null {
-        const clients: Array<any> = Object.values(this.Io.sockets.sockets);
+        const clients: ExSocketInterface[] = Object.values(this.Io.sockets.sockets) as ExSocketInterface[];
         for (let i = 0; i < clients.length; i++) {
-            const client: ExSocketInterface = clients[i];
+            const client = clients[i];
             if (client.token !== token) {
                 continue
             }
@@ -131,20 +150,15 @@ export class IoSocketController {
                         x: user x position on map
                         y: user y position on map
             */
-            socket.on(SockerIoEvent.JOIN_ROOM, (message: any, answerFn): void => {
+            socket.on(SockerIoEvent.JOIN_ROOM, (message: unknown, answerFn): void => {
                 try {
+                    if (!isJoinRoomMessageInterface(message)) {
+                        socket.emit(SockerIoEvent.MESSAGE_ERROR, {message: 'Invalid JOIN_ROOM message.'});
+                        console.warn('Invalid JOIN_ROOM message received: ', message);
+                        return;
+                    }
                     const roomId = message.roomId;
 
-                    if (typeof(roomId) !== 'string') {
-                        socket.emit(SockerIoEvent.MESSAGE_ERROR, {message: 'Expected roomId as a string.'});
-                        return;
-                    }
-                    const position = this.hydratePositionReceive(message.position);
-                    if (position instanceof Error) {
-                        socket.emit(SockerIoEvent.MESSAGE_ERROR, {message: position.message});
-                        return;
-                    }
-
                     const Client = (socket as ExSocketInterface);
 
                     if (Client.roomId === roomId) {
@@ -155,7 +169,7 @@ export class IoSocketController {
                     this.leaveRoom(Client);
 
                     //join new previous room
-                    const world = this.joinRoom(Client, roomId, position);
+                    const world = this.joinRoom(Client, roomId, message.position);
 
                     //add function to refresh position user in real time.
                     //this.refreshUserPosition(Client);
@@ -176,11 +190,11 @@ export class IoSocketController {
                 }
             });
 
-            socket.on(SockerIoEvent.USER_POSITION, (message: any): void => {
+            socket.on(SockerIoEvent.USER_POSITION, (position: unknown): void => {
                 try {
-                    const position = this.hydratePositionReceive(message);
-                    if (position instanceof Error) {
-                        socket.emit(SockerIoEvent.MESSAGE_ERROR, {message: position.message});
+                    if (!isPointInterface(position)) {
+                        socket.emit(SockerIoEvent.MESSAGE_ERROR, {message: 'Invalid USER_POSITION message.'});
+                        console.warn('Invalid USER_POSITION message received: ', position);
                         return;
                     }
 
@@ -204,7 +218,12 @@ export class IoSocketController {
                 }
             });
 
-            socket.on(SockerIoEvent.WEBRTC_SIGNAL, (data: any) => {
+            socket.on(SockerIoEvent.WEBRTC_SIGNAL, (data: unknown) => {
+                if (!isWebRtcSignalMessageInterface(data)) {
+                    socket.emit(SockerIoEvent.MESSAGE_ERROR, {message: 'Invalid WEBRTC_SIGNAL message.'});
+                    console.warn('Invalid WEBRTC_SIGNAL message received: ', data);
+                    return;
+                }
                 //send only at user
                 const client = this.sockets.get(data.receiverId);
                 if (client === undefined) {
@@ -214,16 +233,6 @@ export class IoSocketController {
                 return client.emit(SockerIoEvent.WEBRTC_SIGNAL, data);
             });
 
-            socket.on(SockerIoEvent.WEBRTC_OFFER, (data: any) => {
-                //send only at user
-                const client = this.sockets.get(data.receiverId);
-                if (client === undefined) {
-                    console.warn("While exchanging a WebRTC offer: client with id ", data.receiverId, " does not exist. This might be a race condition.");
-                    return;
-                }
-                client.emit(SockerIoEvent.WEBRTC_OFFER, data);
-            });
-
             socket.on(SockerIoEvent.DISCONNECT, () => {
                 const Client = (socket as ExSocketInterface);
                 try {
@@ -254,7 +263,12 @@ export class IoSocketController {
             });
 
             // Let's send the user id to the user
-            socket.on(SockerIoEvent.SET_PLAYER_DETAILS, (playerDetails: SetPlayerDetailsMessage, answerFn) => {
+            socket.on(SockerIoEvent.SET_PLAYER_DETAILS, (playerDetails: unknown, answerFn) => {
+                if (!isSetPlayerDetailsMessage(playerDetails)) {
+                    socket.emit(SockerIoEvent.MESSAGE_ERROR, {message: 'Invalid SET_PLAYER_DETAILS message.'});
+                    console.warn('Invalid SET_PLAYER_DETAILS message received: ', playerDetails);
+                    return;
+                }
                 const Client = (socket as ExSocketInterface);
                 Client.name = playerDetails.name;
                 Client.character = playerDetails.character;
@@ -288,7 +302,7 @@ export class IoSocketController {
         }
     }
 
-    private joinRoom(Client : ExSocketInterface, roomId: string, position: Point): World {
+    private joinRoom(Client : ExSocketInterface, roomId: string, position: PointInterface): World {
         //join user in room
         Client.join(roomId);
         this.nbClientsPerRoomGauge.inc({ host: os.hostname(), room: roomId });
@@ -343,7 +357,7 @@ export class IoSocketController {
         //send all users in room to create PeerConnection in front
         clients.forEach((client: ExSocketInterface, index: number) => {
 
-            const clientsId = clients.reduce((tabs: Array<any>, clientId: ExSocketInterface, indexClientId: number) => {
+            const clientsId = clients.reduce((tabs: Array<UserInGroupInterface>, clientId: ExSocketInterface, indexClientId: number) => {
                 if (!clientId.userId || clientId.userId === client.userId) {
                     return tabs;
                 }
@@ -359,19 +373,6 @@ export class IoSocketController {
         });
     }
 
-    //Hydrate and manage error
-    hydratePositionReceive(message: any): Point | Error {
-        try {
-            if (!message.x || !message.y || !message.direction || message.moving === undefined) {
-                return new Error("invalid point message sent");
-            }
-            return new Point(message.x, message.y, message.direction, message.moving);
-        } catch (err) {
-            //TODO log error
-            return new Error(err);
-        }
-    }
-
     /** permit to share user position
      ** users position will send in event 'user-position'
      ** The data sent is an array with information for each user :
diff --git a/back/src/Model/Websocket/ExSocketInterface.ts b/back/src/Model/Websocket/ExSocketInterface.ts
index df72321f..e821e296 100644
--- a/back/src/Model/Websocket/ExSocketInterface.ts
+++ b/back/src/Model/Websocket/ExSocketInterface.ts
@@ -1,9 +1,10 @@
 import {Socket} from "socket.io";
 import {PointInterface} from "./PointInterface";
 import {Identificable} from "./Identificable";
+import {TokenInterface} from "../../Controller/AuthenticateController";
 
 export interface ExSocketInterface extends Socket, Identificable {
-    token: any;
+    token: TokenInterface;
     roomId: string;
     webRtcRoomId: string;
     userId: string;
diff --git a/back/src/Model/Websocket/JoinRoomMessage.ts b/back/src/Model/Websocket/JoinRoomMessage.ts
new file mode 100644
index 00000000..16613488
--- /dev/null
+++ b/back/src/Model/Websocket/JoinRoomMessage.ts
@@ -0,0 +1,9 @@
+import * as tg from "generic-type-guard";
+import {isPointInterface} from "./PointInterface";
+
+export const isJoinRoomMessageInterface =
+    new tg.IsInterface().withProperties({
+        roomId: tg.isString,
+        position: isPointInterface,
+    }).get();
+export type JoinRoomMessageInterface = tg.GuardedType<typeof isJoinRoomMessageInterface>;
diff --git a/back/src/Model/Websocket/MessageUserJoined.ts b/back/src/Model/Websocket/MessageUserJoined.ts
index fff9db5d..d3143a6b 100644
--- a/back/src/Model/Websocket/MessageUserJoined.ts
+++ b/back/src/Model/Websocket/MessageUserJoined.ts
@@ -1,4 +1,3 @@
-import {Point} from "./MessageUserPosition";
 import {PointInterface} from "_Model/Websocket/PointInterface";
 
 export class MessageUserJoined {
diff --git a/back/src/Model/Websocket/PointInterface.ts b/back/src/Model/Websocket/PointInterface.ts
index 61b02339..afb07a23 100644
--- a/back/src/Model/Websocket/PointInterface.ts
+++ b/back/src/Model/Websocket/PointInterface.ts
@@ -1,5 +1,17 @@
-export interface PointInterface {
+import * as tg from "generic-type-guard";
+
+/*export interface PointInterface {
     readonly x: number;
     readonly y: number;
     readonly direction: string;
-}
+    readonly moving: boolean;
+}*/
+
+export const isPointInterface =
+    new tg.IsInterface().withProperties({
+        x: tg.isNumber,
+        y: tg.isNumber,
+        direction: tg.isString,
+        moving: tg.isBoolean
+    }).get();
+export type PointInterface = tg.GuardedType<typeof isPointInterface>;
diff --git a/back/src/Model/Websocket/SetPlayerDetailsMessage.ts b/back/src/Model/Websocket/SetPlayerDetailsMessage.ts
index 2f3cc707..21461812 100644
--- a/back/src/Model/Websocket/SetPlayerDetailsMessage.ts
+++ b/back/src/Model/Websocket/SetPlayerDetailsMessage.ts
@@ -1,4 +1,8 @@
-export interface SetPlayerDetailsMessage {
-    name: string,
-    character: string
-}
+import * as tg from "generic-type-guard";
+
+export const isSetPlayerDetailsMessage =
+    new tg.IsInterface().withProperties({
+        name: tg.isString,
+        character: tg.isString
+    }).get();
+export type SetPlayerDetailsMessage = tg.GuardedType<typeof isSetPlayerDetailsMessage>;
diff --git a/back/src/Model/Websocket/UserInGroupInterface.ts b/back/src/Model/Websocket/UserInGroupInterface.ts
new file mode 100644
index 00000000..26cc5fd4
--- /dev/null
+++ b/back/src/Model/Websocket/UserInGroupInterface.ts
@@ -0,0 +1,5 @@
+export interface UserInGroupInterface {
+    userId: string,
+    name: string,
+    initiator: boolean
+}
diff --git a/back/src/Model/Websocket/WebRtcSignalMessage.ts b/back/src/Model/Websocket/WebRtcSignalMessage.ts
new file mode 100644
index 00000000..7edffdfa
--- /dev/null
+++ b/back/src/Model/Websocket/WebRtcSignalMessage.ts
@@ -0,0 +1,10 @@
+import * as tg from "generic-type-guard";
+
+export const isWebRtcSignalMessageInterface =
+    new tg.IsInterface().withProperties({
+        userId: tg.isString,
+        receiverId: tg.isString,
+        roomId: tg.isString,
+        signal: tg.isUnknown
+    }).get();
+export type WebRtcSignalMessageInterface = tg.GuardedType<typeof isWebRtcSignalMessageInterface>;
diff --git a/back/yarn.lock b/back/yarn.lock
index 28223723..f660a5c8 100644
--- a/back/yarn.lock
+++ b/back/yarn.lock
@@ -790,6 +790,11 @@ functional-red-black-tree@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/functional-red-black-tree/-/functional-red-black-tree-1.0.1.tgz#1b0ab3bd553b2a0d6399d29c0e3ea0b252078327"
 
+generic-type-guard@^3.2.0:
+  version "3.2.0"
+  resolved "https://registry.yarnpkg.com/generic-type-guard/-/generic-type-guard-3.2.0.tgz#1fb136f934730c776486526b8a21fe96b067e691"
+  integrity sha512-EkkrXYbOtJ3VPB+SOrU7EhwY65rZErItGtBg5wAqywaj07BOubwOZqMYaxOWekJ9akioGqXIsw1fYk3wwbWsDQ==
+
 get-stdin@^4.0.1:
   version "4.0.1"
   resolved "https://registry.yarnpkg.com/get-stdin/-/get-stdin-4.0.1.tgz#b968c6b0a04384324902e8bf1a5df32579a450fe"