diff --git a/conf/daemon.conf b/conf/daemon.conf
index a177dd0..ff850b6 100644
--- a/conf/daemon.conf
+++ b/conf/daemon.conf
@@ -5,6 +5,10 @@
 # or it can be specified using the -c option
 # example: diya-session-manager -c /path/to/daemon.conf
 
+# PAM service
+# the pam service used for authentication
+pam_service = diya
+
 # Login session command
 # The command to run to start a login session
 # this command will handle the user input and send user
diff --git a/meson.build b/meson.build
index a5d0f08..8e0e74b 100644
--- a/meson.build
+++ b/meson.build
@@ -11,6 +11,7 @@ glib = dependency('glib-2.0')
 gobject = dependency('gobject-2.0')
 gio = dependency('gio-2.0')
 crypt = dependency('libcrypt')
+pam = dependency('pam')
 add_project_arguments(
     [
         '-Wno-pedantic',
@@ -29,10 +30,11 @@ src = [
     'src/configuration.c',
     'src/manager.c',
     'src/base.c',
+    'src/authenticator.c',
     resources
 ]
 
 executable(
     'diya-session-manager',
     src,
-    dependencies: [glib, gobject, gio, crypt])
\ No newline at end of file
+    dependencies: [glib, gobject, gio, crypt, pam])
\ No newline at end of file
diff --git a/src/authenticator.c b/src/authenticator.c
new file mode 100644
index 0000000..ec6b4ea
--- /dev/null
+++ b/src/authenticator.c
@@ -0,0 +1,293 @@
+#include <security/pam_appl.h>
+#include <security/pam_modules.h>
+#include <security/pam_misc.h>
+
+#include "authenticator.h"
+
+struct _SessionAuthenticator
+{
+    BaseObject parent_object;
+    gchar* name;
+    pam_handle_t *pam;
+};
+
+G_DEFINE_FINAL_TYPE(SessionAuthenticator, session_authenticator, BASE_TYPE_OBJECT);
+
+static void session_authenticator_finalize(GObject *object)
+{
+    g_debug("session_authenticator_finalize: %s", base_object_to_string(object));
+    G_OBJECT_CLASS(session_authenticator_parent_class)->finalize(object);
+    SessionAuthenticator *self = SESSION_AUTHENTICATOR(object);
+    if(self->name)
+    {
+        g_free(self->name);
+    }
+    self->name = NULL;
+    if(self->pam)
+    {
+        session_authenticator_close_session(self);
+    }
+}
+
+static void session_authenticator_dispose(GObject *object)
+{
+    g_debug("session_authenticator_dispose: %s", base_object_to_string(object));
+    G_OBJECT_CLASS(session_authenticator_parent_class)->dispose(object);
+}
+
+static const gchar* session_authenticator_to_string(BaseObject *object)
+{
+    (void)object;
+    return "SessionAuthenticator";
+}
+
+static void session_authenticator_class_init(SessionAuthenticatorClass *class)
+{
+    GObjectClass *gobject_class = G_OBJECT_CLASS(class);
+    gobject_class->finalize = session_authenticator_finalize;
+    gobject_class->dispose = session_authenticator_dispose;
+
+    BaseObjectClass *base_class = BASE_OBJECT_CLASS(class);
+    base_class->to_string = session_authenticator_to_string;
+}
+
+static void session_authenticator_init(SessionAuthenticator *self)
+{
+    self->name = NULL;
+    self->pam = NULL;
+}
+
+static int pam_conversation(int num, const struct pam_message **messages, struct pam_response **responses, void *data)
+{
+    g_debug("Initiating conversation between PAM and application");
+
+    /* Check number of responses */
+    if ((num <= 0) || (num > PAM_MAX_NUM_MSG))
+    {
+        g_warning("Invalid number of responses '%d'.", num);
+        return PAM_CONV_ERR;
+    }
+
+    /* Allocate memory for response */
+    struct pam_response *resp;
+
+    if (!(resp = calloc(num, sizeof(*resp))))
+    {
+        return PAM_BUF_ERR;
+    }
+
+    /* Iterate over PAM messages */
+    char **credentials = (char **)data;
+    char *username;
+    char *password;
+    int i;
+
+    for (i = 0; i < num; i++)
+    {
+        switch (messages[i]->msg_style)
+        {
+        case PAM_PROMPT_ECHO_ON:
+            username = credentials[0];
+            resp[i].resp = strdup(username);
+
+            if (!(resp[i].resp))
+            {
+                goto fail;
+            }
+
+            break;
+
+        case PAM_PROMPT_ECHO_OFF:
+            password = credentials[1];
+            resp[i].resp = strdup(password);
+
+            if (!(resp[i].resp))
+            {
+                goto fail;
+            }
+
+            break;
+
+        case PAM_TEXT_INFO:
+            printf("PAM_TEXT_INFO: %s", messages[i]->msg);
+            break;
+
+        case PAM_ERROR_MSG:
+            printf("PAM_ERROR_MSG: %s", messages[i]->msg);
+            break;
+
+        default:
+            goto fail;
+        }
+    }
+
+    *responses = resp;
+
+    g_debug("PAM conversation completed.");
+
+    return PAM_SUCCESS;
+
+/* Goto failure */
+fail:
+    g_debug("PAM conversation failed.");
+
+    for (i = 0; i < num; i++)
+    {
+        if (resp[i].resp)
+        {
+            memset(resp[i].resp, 0, strlen(resp[i].resp));
+            free(resp[i].resp);
+        }
+    }
+
+    memset(resp, 0, num * sizeof(*resp));
+    *responses = 0;
+
+    return PAM_CONV_ERR;
+}
+
+SessionAuthenticator* session_authenticator_new(const char* name)
+{
+    SessionAuthenticator *self = g_object_new(SESSION_TYPE_AUTHENTICATOR, NULL);
+    self->name = g_strdup(name);
+    return self;
+}
+
+gboolean session_authenticator_authenticate(SessionAuthenticator* self, const char* username, const char* password)
+{
+    if(self->pam)
+    {
+        g_critical("PAM session is already opened.");
+        return FALSE;
+    }
+
+    const char *data[2] = {username, password};
+    struct pam_conv conversation = {pam_conversation, data};
+
+    /* Start pam */
+    g_debug("Starting PAM transaction for user %s", username);
+
+    int result = pam_start(self->name, username, &conversation, &self->pam);
+
+    if (result != PAM_SUCCESS)
+    {
+        g_critical("Failed to start PAM transaction: %s", pam_strerror(self->pam, result));
+        session_authenticator_close_session(self);
+        return FALSE;
+    }
+
+    /* Set DISPLAY */
+    result = pam_set_item(self->pam, PAM_XDISPLAY, getenv("DISPLAY"));
+
+    if (result != PAM_SUCCESS)
+    {
+        g_warning("Failed to set PAM_XDISPLAY item: %s", pam_strerror(self->pam, result));
+    }
+
+    /* Set TTY */
+    result = pam_set_item(self->pam, PAM_TTY, getenv("TTY"));
+
+    if (result != PAM_SUCCESS)
+    {
+        g_warning("Failed to set PAM_TTY item: %s", pam_strerror(self->pam, result));
+    }
+
+    /* Set USER */
+    result = pam_set_item(self->pam, PAM_USER, username);
+
+    if (result != PAM_SUCCESS)
+    {
+        g_warning("Failed to set PAM_USER item: %s", pam_strerror(self->pam, result));
+    }
+
+    /* Authenticate pam user */
+    g_debug("Authenticating username %s", username);
+
+    result = pam_authenticate(self->pam, 0);
+
+    if (result != PAM_SUCCESS)
+    {
+        g_critical("Failed to authenticate user: %s", pam_strerror(self->pam, result));
+        session_authenticator_close_session(self);
+        return FALSE;
+    }
+
+    /* Check if user account is valid */
+    result = pam_acct_mgmt(self->pam, 0);
+
+    if (result != PAM_SUCCESS)
+    {
+        g_critical("Failed to manage user account: %s", pam_strerror(self->pam, result));
+        session_authenticator_close_session(self);
+        return FALSE;
+    }
+
+    /* Establish credentials */
+    result = pam_setcred(self->pam, PAM_ESTABLISH_CRED);
+
+    if (result != PAM_SUCCESS)
+    {
+        g_critical("Failed to establish PAM credentials: %s", pam_strerror(self->pam, result));
+        session_authenticator_close_session(self);
+        return FALSE;
+    }
+    return TRUE;
+}
+
+gboolean session_authenticator_is_authenticated(SessionAuthenticator* self)
+{
+    return self->pam != NULL;
+}
+
+gboolean session_authenticator_open_session(SessionAuthenticator* self)
+{
+    g_debug("Preparing to open PAM session.");
+    if(!self->pam)
+    {
+        g_critical("User unauthorized.");
+        return FALSE;
+    }
+
+    int result = pam_open_session(self->pam, 0);
+
+    if (result != PAM_SUCCESS) {
+        g_critical("Failed to open PAM session: %s", pam_strerror(self->pam, result));
+        session_authenticator_close_session(self);
+        return FALSE;
+    }
+    return TRUE;
+}
+
+void session_authenticator_close_session(SessionAuthenticator* self)
+{
+    if(!self->pam)
+    {
+        g_debug("PAM session is not opened.");
+        return;
+    }
+    g_debug("Ending PAM login session");
+
+    /* Close pam session */
+    int result = pam_close_session(self->pam, 0);
+    if (result != PAM_SUCCESS)
+    {
+        g_debug("Failed to close PAM session: %s", pam_strerror(self->pam, result));
+    }
+
+    /* Remove credentials */
+    result = pam_setcred(self->pam, PAM_DELETE_CRED);
+
+    if (result != PAM_SUCCESS)
+    {
+        g_debug("Failed to delete PAM credentials: %s", pam_strerror(self->pam, result));
+    }
+
+    /* End pam session */
+    result = pam_end(self->pam, result);
+
+    if (result != PAM_SUCCESS)
+    {
+        g_debug("Failed to end PAM session: %s", pam_strerror(self->pam, result));
+    }
+    self->pam = NULL;
+}
diff --git a/src/authenticator.h b/src/authenticator.h
new file mode 100644
index 0000000..8f1399e
--- /dev/null
+++ b/src/authenticator.h
@@ -0,0 +1,14 @@
+#ifndef AUTHENTICATOR_H
+#define AUTHENTICATOR_H
+
+#include "base.h"
+
+#define SESSION_TYPE_AUTHENTICATOR (session_authenticator_get_type())
+G_DECLARE_FINAL_TYPE(SessionAuthenticator, session_authenticator, SESSION, AUTHENTICATOR, BaseObject)
+
+SessionAuthenticator* session_authenticator_new(const char* name);
+gboolean session_authenticator_authenticate(SessionAuthenticator* self, const char* username, const char* password);
+gboolean session_authenticator_is_authenticated(SessionAuthenticator* self);
+gboolean session_authenticator_open_session(SessionAuthenticator* self);
+void session_authenticator_close_session(SessionAuthenticator* self);
+#endif
\ No newline at end of file
diff --git a/src/base.c b/src/base.c
index e92c8f3..b93c748 100644
--- a/src/base.c
+++ b/src/base.c
@@ -11,6 +11,12 @@ static void base_object_dispose(GObject* object)
     G_OBJECT_CLASS (base_object_parent_class)->dispose(object);
 }
 
+static void base_object_finalize(GObject* object)
+{
+    g_debug("base_object_finalize");
+    G_OBJECT_CLASS (base_object_parent_class)->finalize(object);
+}
+
 /**
  * @brief Class initialization
  */
@@ -19,6 +25,7 @@ static void base_object_class_init(BaseObjectClass *class)
     GObjectClass *gobject_class = G_OBJECT_CLASS(class);
     class->to_string = NULL;
     gobject_class->dispose = base_object_dispose;
+    gobject_class->finalize = base_object_finalize;
 }
 
 /**
diff --git a/src/configuration.c b/src/configuration.c
index 6a9cca1..6119d50 100644
--- a/src/configuration.c
+++ b/src/configuration.c
@@ -27,18 +27,16 @@ struct _DaemonConfiguration
     gchar* login_session_command;
     gchar* login_session_user;
     gchar* session_command;
+    gchar* pam_service;
     gchar* string;
 };
 
 G_DEFINE_FINAL_TYPE(DaemonConfiguration, daemon_configuration, BASE_TYPE_OBJECT)
 
-/**
- * @brief Dispose the object
- */
-static void daemon_configuration_dispose(GObject* object)
+static void daemon_configuration_finalize(GObject* object)
 {
-    DaemonConfiguration * self = DAEMON_CONFIGURATION(object);
-    g_debug("daemon_configuration_dispose: %s", base_object_to_string(self));
+    g_debug("daemon_configuration_finalize: %s", base_object_to_string(object));
+    DaemonConfiguration *self = DAEMON_CONFIGURATION(object);
     if(self->login_session_command)
     {
         g_free(self->login_session_command);
@@ -51,11 +49,25 @@ static void daemon_configuration_dispose(GObject* object)
     {
         g_free(self->session_command);
     }
+    if(self->pam_service)
+    {
+        g_free(self->pam_service);
+    }
     if(self->string)
     {
         g_free(self->string);
     }
     self->string = NULL;
+    G_OBJECT_CLASS(daemon_configuration_parent_class)->finalize(object);
+}
+
+/**
+ * @brief Dispose the object
+ */
+static void daemon_configuration_dispose(GObject* object)
+{
+    DaemonConfiguration * self = DAEMON_CONFIGURATION(object);
+    g_debug("daemon_configuration_dispose: %s", base_object_to_string(self));
     G_OBJECT_CLASS(daemon_configuration_parent_class)->dispose(object);
 }
 /**
@@ -117,6 +129,7 @@ static void daemon_configuration_class_init(DaemonConfigurationClass *class)
     BaseObjectClass *base_class = BASE_OBJECT_CLASS(class);
 
     gobject_class->dispose = daemon_configuration_dispose;
+    gobject_class->finalize = daemon_configuration_finalize;
     gobject_class->set_property = daemon_configuration_set_property;
     gobject_class->get_property = daemon_configuration_get_property;
 
@@ -137,6 +150,7 @@ static void daemon_configuration_init(DaemonConfiguration *self)
     self->login_session_user = NULL;
     self->session_command = NULL;
     self->string = NULL;
+    self->pam_service = NULL;
 }
 /**
  * @brief Create a new DaemonConfiguration object
@@ -235,6 +249,10 @@ DaemonConfiguration* daemon_configuration_new(const gchar* config_file)
         {
             conf->session_command = g_strdup(value);
         }
+        else if (strncmp(key, "pam_service", 11) == 0)
+        {
+            conf->pam_service = g_strdup(value);
+        }
         else
         {
             g_warning("Ignore unknown configuration: [%s]:[%s]", key, value);
diff --git a/src/manager.c b/src/manager.c
index 37f541d..ece1e18 100644
--- a/src/manager.c
+++ b/src/manager.c
@@ -1,5 +1,6 @@
 #include "manager.h"
 #include "configuration.h"
+#include "authenticator.h"
 #include <gio/gio.h>
 #include <pwd.h>
 #include <grp.h>
@@ -9,6 +10,7 @@
 #include <sys/wait.h>
 
 #define PROCESS_MOM_TO 50 // in ms
+#define DEFAULT_PAM_SERVICE "diya"
 
 #define DBUS_SERVER_NAME "dev.iohub.diya.SessionManager"
 #define DBUS_SERVER_PATH "/dev/iohub/diya/SessionManager"
@@ -47,10 +49,22 @@ struct _SessionManager
     guint bus_id;
     session_manage_state_t state;
     gchar* current_session_user;
+    SessionAuthenticator* authenticator;
 };
 
 G_DEFINE_FINAL_TYPE(SessionManager, session_manager, BASE_TYPE_OBJECT);
 
+static void session_manager_finalize(GObject *object)
+{
+    g_debug("session_manager_finalize: %s", base_object_to_string(object));
+    SessionManager *self = SESSION_MANAGER(object);
+    if (self->current_session_user)
+    {
+        g_free(self->current_session_user);
+    }
+    G_OBJECT_CLASS(session_manager_parent_class)->finalize(object);
+}
+
 /**
  * @brief Dispose the object
  */
@@ -74,9 +88,9 @@ static void session_manager_dispose(GObject *object)
     {
         g_bus_unown_name(self->bus_id);
     }
-    if (self->current_session_user)
+    if(self->authenticator)
     {
-        g_free(self->current_session_user);
+        g_object_unref(self->authenticator);
     }
     G_OBJECT_CLASS(session_manager_parent_class)->dispose(object);
 }
@@ -116,6 +130,7 @@ static void session_manager_class_init(SessionManagerClass *class)
     GObjectClass *gobject_class = G_OBJECT_CLASS(class);
     BaseObjectClass *base_class = BASE_OBJECT_CLASS(class);
     gobject_class->dispose = session_manager_dispose;
+    gobject_class->finalize = session_manager_finalize;
     gobject_class->get_property = session_manager_get_property;
 
     base_class->to_string = session_manager_to_string;
@@ -137,48 +152,12 @@ static void session_manager_init(SessionManager *self)
     self->bus_id = 0;
     self->state = SESSION_MANAGER_STATE_IDLE;
     self->current_session_user = NULL;
+    self->authenticator = NULL;
 }
 
-static gboolean session_user_auth(const char *username, const char *password)
+static gboolean session_user_auth(SessionManager *manager, const char *username, const char *password)
 {
-    char *encrypted;
-    struct passwd *pwd;
-    struct spwd *spwd;
-    /* Look up password and shadow password records for username */
-    pwd = getpwnam(username);
-    if (pwd == NULL)
-    {
-        g_critical("getpwnam: %s", strerror(errno));
-        return FALSE;
-    }
-    spwd = getspnam(username);
-    /*
-    if (spwd == NULL)
-    {
-        g_critical("getspnam: %s", strerror(errno));
-        return FALSE;
-    }
-    */
-
-    if (spwd != NULL) /* If there is a shadow password record */
-    {
-        pwd->pw_passwd = spwd->sp_pwdp; /* Use the shadow password */
-    }
-    /* Encrypt password and erase cleartext version immediately */
-    encrypted = crypt(password, pwd->pw_passwd);
-    if (encrypted == NULL)
-    {
-        g_critical("crypt: %s", strerror(errno));
-        return FALSE;
-    }
-    if (strcmp(encrypted, pwd->pw_passwd) == 0)
-    {
-        return TRUE;
-    }
-    else
-    {
-        return FALSE;
-    }
+    return session_authenticator_authenticate(manager->authenticator, username, password);
 }
 
 static pid_t run_command_as(const gchar* command, const gchar* username)
@@ -200,7 +179,7 @@ static pid_t run_command_as(const gchar* command, const gchar* username)
     }
     if (getgrouplist(username, pwd->pw_gid, g_list, &numgroups) == -1)
     {
-        g_critical("run_command_as: Unable to call getgrouplist: %s", strerror(errno));
+        g_critical("run_command_as: Unable to call getgrouplist for gid %d: %s", pwd->pw_gid, strerror(errno));
         return -1;
     }
     pid_t pid = fork();
@@ -280,6 +259,12 @@ static void start_user_session(SessionManager *self)
         g_critical("start_user_session: session_command is not set in the configuration file, do nothing");
         return;
     }
+    /*
+    if(!session_authenticator_open_session(self->authenticator))
+    {
+        g_critical("start_user_session: Failed to open session");
+        return;
+    }*/
     self->session_pid = run_command_as(session_command, self->current_session_user);
     g_free(session_command);
 }
@@ -315,7 +300,7 @@ static void session_manager_method_call(GDBusConnection *connection, const gchar
             g_dbus_method_invocation_return_dbus_error(invocation, DBUS_SERVER_ERROR_NAME, "A session is currently running");
             return;
         }
-        if(session_user_auth(username, password))
+        if(session_user_auth(self, username, password))
         {
             g_dbus_method_invocation_return_value(invocation, g_variant_new("(b)", TRUE));
             /**
@@ -436,7 +421,15 @@ SessionManager *session_manager_new(const gchar *config_file)
                                      on_name_lost,
                                      manager,
                                      NULL);
-
+    
+    gchar *pam_service = NULL;
+    g_object_get(manager->configuration, "pam_service", &pam_service, NULL);
+    if (pam_service == NULL)
+    {
+        pam_service = g_strdup(DEFAULT_PAM_SERVICE);
+    }
+    manager->authenticator = session_authenticator_new(pam_service);
+    g_free(pam_service);
     return manager;
 }
 
@@ -457,6 +450,8 @@ static void start_login_session(SessionManager *self)
         g_free(self->current_session_user);
         self->current_session_user = NULL;
     }
+    // close old session if any
+    session_authenticator_close_session(self->authenticator);
     gchar *login_session_command = NULL;
     g_object_get(self->configuration, "login-session-command", &login_session_command, NULL);
     if (login_session_command == NULL)
@@ -473,7 +468,7 @@ static void start_login_session(SessionManager *self)
         g_critical("login_session_user is not set in the configuration file, start the login session as root");
         return;
     }
-    
+
     self->login_session_pid = run_command_as(login_session_command, login_session_user);
     g_free(login_session_user);
     g_free(login_session_command);