Estes fontes se referem a dois tutoriais, o de criptografia com QCA e o de bloqueio do sistema após inatividade do mouse e do teclado. 

main.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/


#include <QApplication>
#include "fPrincipal.h"//Para a janela principal do aplicativo
#include <QSettings>//Para leitura do arquivo de configuração
#include <QMessageBox>
#include <QSqlDatabase>//Para acesso ao banco de dados
#include "fLogin.h"//Para a tela de login
#include <QtCrypto>//QCA
#include <QTextCodec>//Para o locale

int main(int argc, char *argv[])
{

  QCA::Initializer init;//Todo aplicativo que usa QCA de ter este código aqui no main.cpp

  QTextCodec::setCodecForTr(QTextCodec:: codecForName ( "UTF-8"));//Para locale
  QTextCodec::setCodecForCStrings(QTextCodec::codecForName("UTF-8")); 
  QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8")); 

  QApplication app(argc, argv);
     

  QString caminho=QCoreApplication::applicationDirPath();//Acha o caminho do binario, no mesmo diretório esta o arquivo config.txt
  caminho.append("/config.txt");

  QString database,host,databasename,linha;
  QSettings settings(caminho,QSettings::IniFormat);//Ler os parâmetros de conexão ao banco no config.txt

  database=settings.value("banco/database").toString();
  host=settings.value("banco/hostname").toString();
  databasename=settings.value("banco/databasename").toString();
    
  if (database=="" || host=="" || databasename=="")
  {
    QMessageBox::information(0,"Iniciando o Sistema","Não foi possivel ler o arquivo de configuração");      
    return 1;
  }
  else
  {
    QSqlDatabase db = QSqlDatabase::addDatabase(database);//Instacia a conexão com os parametros.
    db.setHostName(host);
    db.setDatabaseName(databasename);
    db.setUserName("rodolfo");//Coloque aqui seu usuario no banco
    db.setPassword("%Zh*#u");//Coloque aqui sua senha
    bool ok = db.open();
     
    if (ok)
    {
         
      fPrincipal* fTela_Prin = new fPrincipal(caminho);//Cria o objeto da classe fPrincipal e mostra na tela
      fTela_Prin->show();
       
      bool testa_Login=false;//O endereço desta variavel é passado a tela de login para saber se o login foi correto(usuarios e senhas ok)
      int nivel_Acesso;//Para guardar o nivel de acesso do usuário no aplicativo
      fLogin* fAcesso=new fLogin(0,&testa_Login,&nivel_Acesso);
      fAcesso->exec();
      if (testa_Login==false)//Se o login falhou, destroi os objetos criados e sai do sistema.
      {
        delete fAcesso;
        delete fTela_Prin;
        return 1;
      }
      else//Se o login foi correto, destroi a tela de login.
      {
        fTela_Prin->pega_Nivel(nivel_Acesso);//Passa a janela principal o nive de acessso, que por sua vez passara os demais cadastros.
        delete fAcesso;
      } 
    }
    else
    {
      QMessageBox::information(0,"Iniciando o Sistema","Não foi possivel conectar-se ao banco de dados!");
      return 1; 
    }
  }
  return app.exec();
}

fLogin.h

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *      *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#ifndef FDESBLOQUEIA_LOGIN_H
#define FDESBLOQUEIA_LOGIN_H

#include "ui_fLogin_Parent.h"

class QSqlQuery;
class fLogin:public QDialog,private Ui::fLogin_Parent
{
  Q_OBJECT
  
  public:
    fLogin(QObject *parent = 0,bool* login=false,int* nivel=0);
    ~fLogin();

  private:
    QSqlQuery* query_Login;
    bool* login_2;
    int* niv_Acesso;

    void keyPressEvent(QKeyEvent* e);


  private slots:
    void botao_OK_Click();

  protected:
    class pesq_Senha* testa_Senha;
};

#endif

fLogin.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include "fLogin.h"
#include <QSqlQuery>
#include <QMessageBox>
#include <QKeyEvent>//Para tabular com enter.
#include <QDesktopWidget>
#include "pesq_Senha.h"

fLogin::fLogin(QObject *parent,bool* login,int* nivel)
{
  setupUi(this);

  connect(botao_OK,SIGNAL(clicked()),this,SLOT(botao_OK_Click()));



  this->setFixedSize (this->size());//Para que não se possa redimensionar a janela


  QRect rect = QApplication::desktop()->availableGeometry(this);//para centralizar na tela.
  this->move(rect.center() - this->rect().center());


  edit_Usuario->setFocus();
  
  query_Login=new QSqlQuery;

  login_2=login;
  niv_Acesso=nivel;

  testa_Senha=new pesq_Senha;//Para as funções da QCA
}

fLogin::~fLogin()
{
  delete query_Login;
  delete testa_Senha;
}

void fLogin:: botao_OK_Click()
{
  QString senha=edit_Senha->text();
  QByteArray senha_Hash;  //Abre a tabela de usuários, o parâmetro da consulta é o nome digitado, por isso na tabela a um índice que não permite usuários duplicados.
  query_Login->prepare(" select "
                                " a.id_usuarios,"
                                " a.nome,"
                                " a.senha,"
                                " a.nivel,"
                                " a.tipo_senha, "
                                " b.codigo,"
                                " b.chave, "
                                " b.vetor, "
                                " b.tipo_hash "
                       " from "
                                " usuarios a,"
                                " codigos b "
                       " where "
                                " a.id_usuarios=b.id_codigos and "
                                " a.nome=:nom");
  query_Login->bindValue(":nom",edit_Usuario->text());
  query_Login->exec();
  query_Login->next();
  if (query_Login->size()>0)
  {
    if (query_Login->value(4).toInt()==0)//Testa se a senha é hash ou criptografada.
    {
      senha=senha.append(query_Login->value(5).toString());//Recupera a string aleatória gerada no momento da gravação da senha, e concatena com a senha digitada.
      switch (query_Login->value(8).toInt())//Testa se o padrão do hash e md5 ou sha1.
      {
        case 0:
        {
          senha_Hash=testa_Senha->gera_hash_Senha(senha,0);//Gera o hash da senha digitada
          break;
        }
        case 1:
        {
          senha_Hash=testa_Senha->gera_hash_Senha(senha,1);
          break;
        }
      }
      if (senha_Hash==query_Login->value(2).toByteArray())//Compara o hash da senha digitada com a senha gravada
      {
        *login_2=true;
        *niv_Acesso=query_Login->value(3).toInt();
        this->close();
      }
      else//Se a senha for incorreta, nega o acesso.
      {
        edit_Senha->clear();
        edit_Senha->setFocus();
        QMessageBox::information(0,"Acesso ao Sistema","Senha incorreta!");
      }  
    }
    else
      if (query_Login->value(4).toInt()==1)//Senha criptografada
      {
        if (senha==testa_Senha->descriptografa(query_Login->value(2).toByteArray(),query_Login->value(6).toByteArray(),query_Login->value(7).toByteArray()))//Descriptografa a senha gravada e compara com a digitada.A rotina usa como parâmetros a senha gravada, a chave o vetor gerados e gravados no banco.
        {
          *login_2=true;//Acerta os valores de vivel de acesso e login correto.
          *niv_Acesso=query_Login->value(3).toInt();
          this->close();
        }
        else
        {
          edit_Senha->clear();
          edit_Senha->setFocus();
          QMessageBox::information(0,"Acesso ao Sistema","Senha incorreta!");
        }
      }
      else
        QMessageBox::information(0,"Acesso ao Sistema","Tipo de senha desconhecido!");
  }  
  else
  { 
    edit_Usuario->setFocus();
    QMessageBox::information(0,"Acesso ao Sistema","Usúario não existe no banco de dados!");
  }  
}

void fLogin::keyPressEvent(QKeyEvent* e)
{
  if ( e->key() == Qt::Key_Enter || e->key() == Qt::Key_Return )//Tabula com enter.
    QApplication::focusWidget()->nextInFocusChain()->setFocus();
}

fPrincipal.h

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/


#ifndef FPRINCIPAL_H
#define FPRINCIPAL_H

#include "ui_fPrincipal_Parent.h"

class fPrincipal:public QMainWindow,private Ui::fPrincipal_Parent
{
  Q_OBJECT

  public:
    fPrincipal(QString caminho="");
    ~fPrincipal();

    void pega_Nivel(int pegNivel);//Declara a função que pega o nivel de acesso.

  protected:
    class trava_Sistema* trava_Sis;
    class fCadClientes* fCadCli;
    class fCadUsuarios* fCadUs;//Declara o cadastro de usuários.

  private slots:
    void on_actionClientes_triggered();
    void on_action_Usuarios_triggered();//Slot que ira instanciar o objeto da classe  fCadUsuarios.

  private:
    void mouseMoveEvent(QMouseEvent * event);
    void keyPressEvent(QKeyEvent* e);

    int nivel;


};

#endif


fPrincipal.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/


#include "fPrincipal.h"
#include <QDesktopWidget>
#include "trava_Sistema.h"
#include "fCadClientes.h"
#include "fCadUsuarios.h"

fPrincipal::fPrincipal(QString caminho)
{
  setupUi(this);

  this->setAttribute(Qt::WA_DeleteOnClose,true);//para auto destruir o objeto e liberar a memoria.

  QRect rect = QApplication::desktop()->availableGeometry(this);//para centralizar na tela.
  this->move(rect.center() - this->rect().center());

  this->setFixedSize (this->size());//Para que não se possa redimensionar a janela

  trava_Sis=new trava_Sistema(this,caminho);//Instancia um objeto da classe trava_Sistema, que tem os métodos para bloquear o sistema

  centralwidget->setMouseTracking(true);//Você deve colocar esta linha, pois no ui_fPrincipal_Parent.h, ele define centralwidget = new QWidget(fPrincipal_Parent);     centralwidget->setObjectName(QString::fromUtf8("centralwidget")); Então quem responde por capturar corretamente o evento do mouse é centralwidget.

}


fPrincipal::~fPrincipal()
{
  delete trava_Sis;
}

void  fPrincipal::keyPressEvent(QKeyEvent* e)
{
  trava_Sis->reinicia_Timer();//Ao usar o teclado, zera o timer
}

void fPrincipal::mouseMoveEvent ( QMouseEvent * event )
{
  trava_Sis->reinicia_Timer();//Ao mover o mouse, zera o timer
}

void fPrincipal::on_actionClientes_triggered()
{
  fCadCli=new fCadClientes(this,trava_Sis);//Passa o objeto trava_Sis como parâmetro para o objeto instanciado, no caso um cadastro.
  fCadCli->show();
}

void fPrincipal::on_action_Usuarios_triggered()
{
  fCadUs=new fCadUsuarios(this,nivel);//Instancia o cadastro de usuários.
  fCadUs->show();
}

void fPrincipal::pega_Nivel(int pegNivel)
{
  nivel=pegNivel;//Acerta a variavel nivel com o valor de pegNivel que vem do main.cpp

}

fCadUsuarios.h

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/


#ifndef FCADUSUARIOS_H
#define FCADUSUARIOS_H

#include "ui_fCadUsuarios_Parent.h"

class QSqlQuery;
class QSqlQueryModel;
class QSqlDatabase;
class QSignalMapper;

class fCadUsuarios:public QWidget,private Ui::fCadUsuarios_Parent
{
  Q_OBJECT
  
  public:
    fCadUsuarios(QWidget* parent=0,int nivel=0);
    ~fCadUsuarios();

  private:
    QButtonGroup* group_Tipo_Senha;
    QButtonGroup* group_Tipo_Hash;
    QSqlQuery* query_Usuarios;//Nossa query de trabalho.
    QSqlQueryModel* model_Usuarios;//Um grid para mostrar os dados
    int gera_Aleatorio(int min,int max,int semente);//Função C++ para gerar numeros aleatorios.
    QSignalMapper* signalMapper;

  private slots:
    void tipo_Senha();
    void grava_na_Tabela(int tipo);
    void exclui_na_Tabela();
    void limpa_Tela();

  protected:
    class pesq_Senha* testa_Senha;//Declara um objeto da classe abstrata pesq_Senha que tem as funções da QCA.
  
};


#endif

fCadUsuarios.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include "fCadUsuarios.h"
#include <QDesktopWidget>
#include <QButtonGroup>
#include <QSqlQueryModel>
#include <QSqlQuery>
#include <QtCrypto>
#include <QMessageBox>
#include <QSqlError>
#include "pesq_Senha.h"
#include <QSignalMapper>

fCadUsuarios::fCadUsuarios(QWidget* parent,int nivel)
{
  setupUi(this);

  this->setAttribute(Qt::WA_DeleteOnClose,true);//para auto destruir o objeto e liberar a memoria.

  QRect rect = QApplication::desktop()->availableGeometry(this);//para centralizar na tela.
  this->move(rect.center() - this->rect().center());

  this->setFixedSize (this->size());//Para que não se possa redimensionar a janela

  if (nivel>1)//Bloqueia o acesso aos botões conforme o nivel do usuário.
  {
    botao_Incluir->setEnabled(false);
    botao_Alterar->setEnabled(false);
    botao_Excluir->setEnabled(false);
  }

  testa_Senha=new pesq_Senha;//Instancia um objeto da classe pesq_Senha.

  group_Tipo_Senha=new QButtonGroup(this);//cria o QbuttonGroup
  group_Tipo_Senha->setExclusive(true);//clicou em um, desmarcou o outro
  group_Tipo_Senha->addButton(botao_hash);//adiciona o RadioButton ao QbuttonGroup
  group_Tipo_Senha->setId(botao_hash,0);// indice do RadioButton dentro do QbuttonGroup
  group_Tipo_Senha->addButton(botao_Cripto);
  group_Tipo_Senha->setId(botao_Cripto,1);

  connect(group_Tipo_Senha,SIGNAL(buttonClicked(int)),this,SLOT(tipo_Senha()));

  group_Tipo_Hash=new QButtonGroup(this);
  group_Tipo_Hash->setExclusive(true);//clicou em um, desmarcou o outro
  group_Tipo_Hash->addButton(botao_sha1);//adiciona o RadioButton ao QbuttonGroup
  group_Tipo_Hash->setId(botao_sha1,0);// indice do RadioButton dentro do QbuttonGroup
  group_Tipo_Hash->addButton(botao_md5);
  group_Tipo_Hash->setId(botao_md5,1);

  signalMapper = new QSignalMapper(this);//Para que os botões incluir e alterar acessem o mesmo slot e se saiba qual botão esta acessando.
  signalMapper->setMapping(botao_Incluir, 1);
  signalMapper->setMapping(botao_Alterar, 2);

  connect(botao_Incluir,SIGNAL(clicked()),signalMapper,SLOT (map()));
  connect(botao_Alterar,SIGNAL(clicked()),signalMapper,SLOT (map()));

  connect(signalMapper, SIGNAL(mapped(int )),this,SLOT(grava_na_Tabela(int )));


  connect(botao_Excluir,SIGNAL(clicked()),this,SLOT(exclui_na_Tabela()));
  connect(botao_limpar_Tela,SIGNAL(clicked()),this,SLOT(limpa_Tela()));

  query_Usuarios=new QSqlQuery;

  model_Usuarios=new QSqlQueryModel(this);
  model_Usuarios->setQuery("select * from usuarios order by id_usuarios");
  model_Usuarios->setHeaderData(0, Qt::Horizontal, tr("Código"));
  model_Usuarios->setHeaderData(1, Qt::Horizontal, tr("Nome"));
  model_Usuarios->setHeaderData(2, Qt::Horizontal, tr("Senha"));
  model_Usuarios->setHeaderData(3, Qt::Horizontal, tr("Nivel"));

  tableView_Usuarios->setModel(model_Usuarios);//Conecta o model ao tableView para visualizarmos a tabela.
  tableView_Usuarios->setColumnWidth(0,40);
  tableView_Usuarios->setColumnWidth(1,80);
  tableView_Usuarios->setColumnWidth(2,270);
  tableView_Usuarios->setColumnWidth(3,40);
  tableView_Usuarios->show();

  edit_Codigo->setFocus(); 


}

fCadUsuarios::~fCadUsuarios()
{
  delete group_Tipo_Senha;
  delete testa_Senha;
  delete group_Tipo_Hash;
  delete query_Usuarios;
  delete model_Usuarios;
  delete signalMapper;
}

void fCadUsuarios::tipo_Senha()
{
  switch (group_Tipo_Senha->checkedId())//Bloqueia alternadamente as opções de hash e criptografada.
  {
    case 0:
    {
      group_hash->setEnabled(true);
      break;
    }
    case 1:
    {
      group_hash->setEnabled(false);
      break;
    }
  }
  
}

void fCadUsuarios::grava_na_Tabela(int tipo)
{

  QString senha;
  senha=edit_Senha->text();
  QByteArray senha_Cripto;
  QString complemento="0";
  QByteArray* chave_Usuario=new QByteArray;
  QByteArray* vetor_Usuario=new QByteArray;

  switch (group_Tipo_Senha->checkedId())//Testa se a senha sera hash ou criptografada.
  {
    case 0:
    {
      
      int j,k;
      //gera uma sequencia de 10 numeros aleatorios, de 65 a 90, seus characters ASCII correspondestes são concatenados em uma string que por sua vez é concatenada à senha digitada.Isto serve para evitar senhas iguais.
      for (j=1;j<=10;j++)
      {
        k=gera_Aleatorio(65,90,j);
        complemento[j]=QChar(k);
      }
      QMessageBox::information(0,"Sistema de Criptografia",complemento);
      senha=senha.append(complemento);
      switch (group_Tipo_Hash->checkedId())//Testa se o hash é sha1 ou md5.
      {
        case 0:
        {
          senha_Cripto=testa_Senha->gera_hash_Senha(senha,0);//Gera o hash conforme o tipo.
          break;
        }
        case 1:
        {
          senha_Cripto=testa_Senha->gera_hash_Senha(senha,1);
          break;
        }
      }
      break;
    }
    case 1:
    {
      senha_Cripto=testa_Senha->criptografa(senha,chave_Usuario,vetor_Usuario);//Senha criptografada.
      break;
    }
  }

  bool gravou=false;
  QString erro;

  //Abaixo, o código que ira gravar a senha na tabela. O objeto QSqlQuery ira chamar uma procedure no banco(PostgreSql) que ira gravar nas duas tabelas, usuários e códigos, na tabela usuários sera gravada o nome, a senha, o tipo de senha, se hash ou criptografada, o nível de acesso dentro do sistema, na tabela códigos sera gravada o complemento e a chave e vetor no caso de senha criptografada. São duas procedures, uma para inserir e outra para alterar.


  if (tipo==1)//Testa se esta incluindo ou alterando.
    query_Usuarios->prepare("select insere_Usuario(:cod,:nom,:sen,:niv,:tp,:comp,:chv,:vet,:hash)");
  else
    if (tipo==2)
      query_Usuarios->prepare("select altera_Usuario(:cod,:nom,:sen,:niv,:tp,:comp,:chv,:vet,:hash)");
  query_Usuarios->bindValue(":cod", edit_Codigo->text());//Parâmetros.
  query_Usuarios->bindValue(":nom", edit_Nome->text());
  query_Usuarios->bindValue(":sen",senha_Cripto);
  query_Usuarios->bindValue(":niv", combo_Nivel->currentIndex()+1);
  switch (group_Tipo_Senha->checkedId())
  {
    case 0:
    {
      query_Usuarios->bindValue(":tp", 0);
      query_Usuarios->bindValue(":chv","0");
      query_Usuarios->bindValue(":vet","0");
      switch (group_Tipo_Hash->checkedId())
      {
        case 0:
        {
          query_Usuarios->bindValue(":hash",0);
          break;
        }
        case 1:
        {
          query_Usuarios->bindValue(":hash",1);
          break;
        }
      }      
      break;
    }
    case 1:
    {
      query_Usuarios->bindValue(":tp",1);
      query_Usuarios->bindValue(":chv",*chave_Usuario);
      query_Usuarios->bindValue(":vet",*vetor_Usuario);
      query_Usuarios->bindValue(":hash",0);
      break;
    }      
  }
  query_Usuarios->bindValue(":comp",complemento);
  gravou=query_Usuarios->exec();
  if (! gravou)
  {
    erro=query_Usuarios->lastError().text();
    QMessageBox::critical(0,"Sistema de Criptografia",erro,QMessageBox::Cancel);
  }
  delete chave_Usuario;
  delete vetor_Usuario;
  /*bool gravou,gravou2=false;
  QSqlDatabase::database().transaction();

  QString erro;

  //Aqui é auto evidente o que o codigo faz, grava na tabela.
  query_Usuarios->prepare(" insert into usuarios (id_usuarios,nome,senha,nivel,tipo_senha) values (:cod,:nom,:sen,:niv,:tp) ");
  query_Usuarios->bindValue(":cod", edit_Codigo->text());//Parâmetros.
  query_Usuarios->bindValue(":nom", edit_Nome->text());
  query_Usuarios->bindValue(":sen",senha);
  query_Usuarios->bindValue(":niv", 1);
  switch (group_Tipo_Senha->checkedId())
  {
    case 0:
    {
      query_Usuarios->bindValue(":tp", 0);
      break;
    }
    case 1:
    {
      query_Usuarios->bindValue(":tp", 1);
      break;
    }      
  }
  gravou=query_Usuarios->exec();
  if (! gravou)
  {
    erro=query_Usuarios->lastError().text();
    erro.append(" ");
  }
  QSqlQuery* query_Complemento=new QSqlQuery;
  query_Complemento->prepare(" insert into codigos (id_codigos,codigo,chave) values (:id,:cod,:chv) ");
  query_Complemento->bindValue(":id", edit_Codigo->text());
  query_Complemento->bindValue(":cod",complemento);
  switch (group_Tipo_Senha->checkedId())
  {
    case 0:
    {
      query_Usuarios->bindValue(":chv","0");
      break;
    }
    case 1:
    {
      query_Usuarios->bindValue(":chv",*chave_Usuario);
      break;
    }      
  }
  gravou2=query_Complemento->exec();
  
  if (gravou && gravou2)
    QSqlDatabase::database().commit();
  else
  {
    QSqlDatabase::database().rollback();
    erro.append(query_Complemento->lastError().text());
    QMessageBox::critical(0,"Sistema de Criptografia",erro,QMessageBox::Cancel);
  }*/

  model_Usuarios->setQuery("select * from usuarios order by id_usuarios");//Atualiza o grid
  tableView_Usuarios->show();
  limpa_Tela();
}


void fCadUsuarios::exclui_na_Tabela()
{
  query_Usuarios->prepare("delete from usuarios where id_usuarios=:cod");

  query_Usuarios->bindValue(":cod", edit_Codigo->text());
  if (!query_Usuarios->exec())
    QMessageBox::critical(0,"Sistema de Criptografia",query_Usuarios->lastError().text(),QMessageBox::Cancel); 

  model_Usuarios->setQuery("select * from usuarios order by id_usuarios");
  tableView_Usuarios->show();
  limpa_Tela();
}

void fCadUsuarios::limpa_Tela()
{
  //Limpa os campos de edição.
  edit_Codigo->clear();
  edit_Nome->clear();
  edit_Senha->clear();
  edit_Codigo->setFocus();
}

int fCadUsuarios::gera_Aleatorio(int min,int max,int semente)
{

  int r;

  if(!semente)
  {
    srand((unsigned)semente);
  }

  r=min+rand()%(max-min+1);
  
  return r;
}

pesq_Senha.h

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#ifndef PESQ_SENHA_H
#define PESQ_SENHA_H


class QString;
class QByteArray;
class pesq_Senha
{
  public:
    pesq_Senha();
    ~pesq_Senha();
    QByteArray gera_hash_Senha(QString senha,int tipo_Hash);
    QString descriptografa(QByteArray senha,QByteArray chave_Usuario,QByteArray vetor_Usuario);
    QByteArray criptografa(QString senha,QByteArray* chave_Usuario,QByteArray* vetor_Usuario);
};


#endif

pesq_Senha.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include "pesq_Senha.h"
#include <QString>
#include <QMessageBox>
#include <QtCrypto>

pesq_Senha::pesq_Senha()
{
}

pesq_Senha::~pesq_Senha()
{
}

QByteArray pesq_Senha::gera_hash_Senha(QString senha,int tipo_hash) 
{
  QByteArray result="";
  QCA::SecureArray arg = senha.toAscii();
  int meio=arg.size()/2;
  switch (tipo_hash)
  {
    case 0:
    {
      if( !QCA::isSupported("sha1") )
        QMessageBox::information(0,"Sistema de Criptografia","SHA1 não suportado");
      else
      {
       QCA::Hash senha_hash("sha1");
       senha_hash.update(senha.toAscii());
       result=senha_hash.final().toByteArray();
      }
      break;
    }
    case 1:
    {
      if( !QCA::isSupported("md5") )
        QMessageBox::information(0,"Sistema de Criptografia","MD5 não suportado");
      else
      {
        QCA::SecureArray part1(arg.toByteArray().left(meio)); 
        QCA::SecureArray part2(arg.toByteArray().mid(meio)); 

        QCA::Hash hashObject("md5");
        hashObject.update(part1);
        hashObject.update(part2);
        QCA::SecureArray resultArray = hashObject.final();
        result = resultArray.toByteArray();
        break;
      }
    }
  }
  return result;
}

QString pesq_Senha::descriptografa(QByteArray senha,QByteArray chave_Usuario,QByteArray vetor_Usuario)
{
  QString result="";

  if(!QCA::isSupported("aes128-cbc-pkcs7"))
    QMessageBox::information(0,"Sistema de Criptografia","Método AES128-CBC não suportado"); 
  else
  {
    QByteArray chave=chave_Usuario;
    QCA::SymmetricKey key(chave);

    QByteArray vetor=vetor_Usuario;
    QCA::InitializationVector iv(vetor);

    QCA::Cipher cipher(QString("aes128"),QCA::Cipher::CBC,QCA::Cipher::DefaultPadding,QCA::Encode,key,iv);

    cipher.setup( QCA::Decode, key, iv );
        
    QCA::SecureArray cipherText = senha;

    QCA::SecureArray plainText = cipher.update(cipherText);

    if (!cipher.ok()) 
    {
      QMessageBox::information(0,"Sistema de Criptografia","Update falhou");
    }

    plainText = cipher.final();
    if (!cipher.ok())
    {
      QMessageBox::information(0,"Sistema de Criptografia","Final falhou");
    }

    result=plainText.data();
  }

  return result;
}

QByteArray pesq_Senha::criptografa(QString senha,QByteArray* chave_Usuario,QByteArray* vetor_Usuario)
{
  QByteArray result;
  
  QCA::SymmetricKey key(16);
  *chave_Usuario=key.toByteArray();

  
  QCA::InitializationVector iv(16);
  *vetor_Usuario=iv.toByteArray();

  QCA::SecureArray arg=senha.toAscii();

  QCA::Cipher cipher(QString("aes128"),QCA::Cipher::CBC,QCA::Cipher::DefaultPadding,QCA::Encode,key,iv);
  QCA::SecureArray u = cipher.update(arg);

  if (!cipher.ok())
  {
    QMessageBox::information(0,"Sistema de Criptografia","Update falhou");
    result="";
  }
  else
  {

    QCA::SecureArray f = cipher.final();

    if (!cipher.ok())
    {
      QMessageBox::information(0,"Sistema de Criptografia","Final falhou");
      result="";
    }
    else
    {
      QCA::SecureArray cipherText = u.append(f);
      result=cipherText.toByteArray();
    }
  }
  return result;

}

fCadClientes.h

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#ifndef FCADCLIENTES_H
#define FCADCLIENTES_H

#include "ui_fCadClientes_Parent.h"

class trava_Sistema;
class fCadClientes:public QWidget,private Ui::fCadClientes_Parent
{
  Q_OBJECT

  public:
    fCadClientes(QWidget* parent=0,trava_Sistema* tr_Sis=0);
    ~fCadClientes();

  protected:
    class trava_Sistema* trava_Sis;

  private:
    void mouseMoveEvent(QMouseEvent * event);
    void keyPressEvent(QKeyEvent* e);
};


#endif

fCadClientes.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/


#include "fCadClientes.h"
#include <QDesktopWidget>
#include "trava_Sistema.h"

fCadClientes::fCadClientes(QWidget* parent,trava_Sistema* tr_Sis)
{
  setupUi(this);

  this->setAttribute(Qt::WA_DeleteOnClose,true);//para auto destruir o objeto e liberar a memoria.

  QRect rect = QApplication::desktop()->availableGeometry(this);//para centralizar na tela.
  this->move(rect.center() - this->rect().center());

  this->setFixedSize (this->size());//Para que não se possa redimensionar a janela

  trava_Sis=tr_Sis;//Passa o endereço do objeto da classe trava_Sistema instanciado na tela principal para a variavel tr_Sis.
}

fCadClientes::~fCadClientes()
{
}

void fCadClientes::mouseMoveEvent(QMouseEvent * event)
{
  trava_Sis->reinicia_Timer();//reseta o objeto QTimer e o inicia de novo, assim que o mouse é movimentado.
}

void fCadClientes::keyPressEvent(QKeyEvent* e)
{
  trava_Sis->reinicia_Timer();//reseta o objeto QTimer e o inicia de novo, assim que o teclado é usado.
}

fDesbloqueia_Sistema.h

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#ifndef FDESBLOQUEIA_SISTEMA_H
#define FDESBLOQUEIA_SISTEMA_H

#include "ui_fLogin_Parent.h"

class QSqlQuery;
class fDesbloqueia_Sistema:public QDialog,private Ui::fLogin_Parent
{
  Q_OBJECT

  public:
    fDesbloqueia_Sistema(QObject *parent=0,bool* login=0);
    ~fDesbloqueia_Sistema();

  private:
    void closeEvent ( QCloseEvent * event );
    bool senha_Correta;
    QSqlQuery* query_Login;

    void keyPressEvent(QKeyEvent* e);


  private slots:
    void botao_OK_Click();

  protected:
    class pesq_Senha* testa_Senha;
};


#endif

fDesbloqueia_Sistema.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   rodolfo@Programador   *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include "fDesbloqueia_Sistema.h"
#include <QCloseEvent>
#include <QSqlQuery>
#include <QMessageBox>
#include <QDesktopWidget>
#include "pesq_Senha.h"

fDesbloqueia_Sistema::fDesbloqueia_Sistema(QObject *parent,bool* login)
{
  setupUi(this);

  this->setAttribute(Qt::WA_DeleteOnClose,true);

  senha_Correta=false;

  connect(botao_OK,SIGNAL(clicked()),this,SLOT(botao_OK_Click()));



  this->setFixedSize (this->size());//Para que não se possa redimensionar a janela


  QRect rect = QApplication::desktop()->availableGeometry(this);//para centralizar na tela.
  this->move(rect.center() - this->rect().center());


  edit_Usuario->setFocus();
  
  query_Login=new QSqlQuery;

  testa_Senha=new pesq_Senha;
}

fDesbloqueia_Sistema::~fDesbloqueia_Sistema()
{
  delete query_Login;
  delete testa_Senha;
}

void fDesbloqueia_Sistema:: botao_OK_Click()
{
  QString senha=edit_Senha->text();
  QByteArray senha_Hash;
  //Abre a tabela de usuários, o parâmetro da consulta é o nome digitado, por isso na tabela a um índice que não permite usuários duplicados.
  query_Login->prepare(" select "
                                " a.id_usuarios,"
                                " a.nome,"
                                " a.senha,"
                                " a.nivel,"
                                " a.tipo_senha, "
                                " b.codigo,"
                                " b.chave, "
                                " b.vetor, "
                                " b.tipo_hash "
                       " from "
                                " usuarios a,"
                                " codigos b "
                       " where "
                                " a.id_usuarios=b.id_codigos and "
                                " a.nome=:nom");
  query_Login->bindValue(":nom",edit_Usuario->text());
  query_Login->exec();
  query_Login->next();
  if (query_Login->size()>0)
  {
    if (query_Login->value(4).toInt()==0)//Testa se a senha é hash ou criptografada.
    {
      //hash
      senha=senha.append(query_Login->value(5).toString());//Recupera a string aleatória gerada no momento da gravação da senha, e concatena com a senha digitada.
      switch (query_Login->value(8).toInt())//Testa se o padrão do hash e md5 ou sha1.
      {
        case 0:
        {
          senha_Hash=testa_Senha->gera_hash_Senha(senha,0);//Gera o hash da senha digitada
          break;
        }
        case 1:
        {
          senha_Hash=testa_Senha->gera_hash_Senha(senha,1);
          break;
        }
      }
      if (senha_Hash==query_Login->value(2).toByteArray())//Compara o hash da senha digitada com a senha gravada
      {
        senha_Correta=true;
        this->close();
      }
      else
      {
        edit_Senha->clear();
        edit_Senha->setFocus();
        QMessageBox::information(0,"Acesso ao Sistema","Senha incorreta!");
      }  
    }
    else
      if (query_Login->value(4).toInt()==1)//Senha criptografada
      {
        if (senha==testa_Senha->descriptografa(query_Login->value(2).toByteArray(),query_Login->value(6).toByteArray(),query_Login->value(7).toByteArray()))//Descriptografa a senha gravada e compara com a digitada.A rotina usa como parâmetros a senha digitada, a chave o vetor gerados e gravados no banco.
        {
          senha_Correta=true;
          this->close();
        }
        else
        {
          edit_Senha->clear();
          edit_Senha->setFocus();
          QMessageBox::information(0,"Acesso ao Sistema","Senha incorreta!");
        }
      }
      else
        QMessageBox::information(0,"Acesso ao Sistema","Tipo de senha desconhecido!");
  }  
  else
  { 
    edit_Usuario->setFocus();
    QMessageBox::information(0,"Acesso ao Sistema","Usúario não existe no banco de dados!");
  }  
 
}

void fDesbloqueia_Sistema::keyPressEvent(QKeyEvent* e)
{
  if ( e->key() == Qt::Key_Enter || e->key() == Qt::Key_Return )//Tabula com enter.
    QApplication::focusWidget()->nextInFocusChain()->setFocus();
}

void fDesbloqueia_Sistema::closeEvent( QCloseEvent * event )
{
  if (senha_Correta)//Não deixa fechar se a senha é incorreta.
    event->accept();
  else
    event->ignore();

}

trava_Sistema.h

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#ifndef TRAVA_SISTEMA_H
#define TRAVA_SISTEMA_H

#include <QObject>
#include "fDesbloqueia_Sistema.h"

class QTimer;

class trava_Sistema:public QObject
{
  Q_OBJECT
  public:
    trava_Sistema(QWidget *parent = 0,QString caminho="");
    ~trava_Sistema();
 
  public slots:
   void reinicia_Timer(); 

  private:
    QTimer* timer;
    int tempo;

  private slots:
    void chama_Login();
  
  protected:
    class fDesbloqueia_Sistema* fDestrava_Sis;
};


#endif

trava_Sistema.cpp

/***************************************************************************
 *   Copyright (C) 2009 by Rodolfo Ribeiro Machado   *
 *   
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include "trava_Sistema.h"
#include <QTimer>
#include "fDesbloqueia_Sistema.h"
#include <QSettings>

trava_Sistema::trava_Sistema(QWidget *parent,QString caminho)
{
  QSettings settings(caminho,QSettings::IniFormat);

  tempo=settings.value("timer/tempo").toInt();//Lê no arquivo config.txt o valor de tempo para bloquear o sistema.
   
  timer=new QTimer;
  timer->start(tempo);

  connect(timer,SIGNAL(timeout()),this,SLOT(chama_Login()));
}

trava_Sistema::~trava_Sistema()
{
  delete timer;
}

void trava_Sistema::reinicia_Timer()
{
  timer->stop();
  timer->start(tempo);
}

void trava_Sistema::chama_Login()
{
  timer->stop();//Ao chamar a tela de login, para de correr o tempo.
  bool login=false;
  fDestrava_Sis=new fDesbloqueia_Sistema(this,&login);//Instancia e abre a tela de login.
  connect(fDestrava_Sis,SIGNAL(destroyed()),this,SLOT(reinicia_Timer()));//Quando a tela de login se fecha, o tempo começa a correr de novo.
  fDestrava_Sis->show();
}


Script para gerar o banco:

create language plpgsql;

create table usuarios(
id_usuarios int primary key,
nome varchar(20) unique not null check (nome <> ''),
senha bytea not null,
nivel int not null check (nivel >= 1),
tipo_senha integer not null check (tipo_senha >= 0 and tipo_senha<=1));


create table codigos(
id_codigos int primary key,
codigo varchar(100) not null check (codigo <> ''),
chave bytea not null,
vetor bytea not null,
tipo_hash integer not null check (tipo_hash >= 0 and tipo_hash <=1));

alter table codigos add FOREIGN KEY (id_codigos) references usuarios(id_usuarios);

CREATE OR REPLACE FUNCTION deleta_Complemento() RETURNS trigger AS $deleta_Complemento$
BEGIN
   delete from
     codigos
   where
     id_codigos=old.id_usuarios;
  return OLD;
END;
$deleta_Complemento$ LANGUAGE plpgsql; 

CREATE TRIGGER deleta_Complemento BEFORE DELETE ON usuarios
FOR EACH ROW EXECUTE PROCEDURE deleta_Complemento();


CREATE OR REPLACE FUNCTION insere_Usuario(integer,varchar(20),bytea,integer,integer,varchar(100),bytea,bytea,integer)
RETURNS void
AS '
insert into
  usuarios
  (id_usuarios,
   nome,
   senha,
   nivel,
   tipo_senha)
values
  ($1,$2,$3,$4,$5);
insert into
  codigos
  (id_codigos,
   codigo,
   chave,
   vetor,
   tipo_hash)
values
  ($1,$6,$7,$8,$9);
' LANGUAGE SQL;

CREATE OR REPLACE FUNCTION altera_Usuario(integer,varchar(20),bytea,integer,integer,varchar(100),bytea,bytea,integer)
RETURNS void
AS '
update
  usuarios
set
   nome=$2,
   senha=$3,
   nivel=$4,
   tipo_senha=$5
where
    id_usuarios=$1;
update
  codigos
set
    codigo=$6,
    chave=$7,
    vetor=$8,
    tipo_hash=$9
where
    id_codigos=$1;
' LANGUAGE SQL;

arquivo config.txt:

[banco]
database = QPSQL
hostname = localhost
databasename = teste_senha
[timer]
tempo =100000