[Aide] Code PHP pour décrypter du SHA1

<?php 
		if (isset($_POST['updatePassBtn']))
		{
			$cpassword = $_POST['cpassword'];
			$npassword = $_POST['npassword'];
			$rpassword = $_POST['rpassword'];
			if (!empty($cpassword) && !empty($npassword) && !empty($rpassword))
			{
				if ($npassword == $rpassword)
				{
					$SQLCheckCurrent = $odb -> prepare("SELECT COUNT(*) FROM `users` WHERE `username` = :username AND `password` = :password");
					$SQLCheckCurrent -> execute(array(':username' => $_SESSION['username'], ':password' => SHA1($cpassword)));
					$countCurrent = $SQLCheckCurrent -> fetchColumn(0);
					if ($countCurrent == 1)
					{
						$SQLUpdate = $odb -> prepare("UPDATE `users` SET `password` = :password WHERE `username` = :username AND `ID` = :id");
						$SQLUpdate -> execute(array(':password' => SHA1($npassword),':username' => $_SESSION['username'], ':id' => $_SESSION['ID']));
						echo '<div class="alert alert-success"><p><strong>BRAVO: </strong>Mot de passe mis à jours</p></div>';
					}
					else
					{
						echo '<div class="alert alert-error"><p><strong>ERREUR: </strong>Mot de passe actuel incorrecte.</p></div>';
					}
				}
				else
				{
					echo '<div class="alert alert-error"><p><strong>ERREUR: </strong>Les mot de passes ne correspondent pas.</p></div>';
				}
			}
			else
			{
				echo '<div class="alert alert-error"><p><strong>ERREUR: </strong>Vérifier les champs</p></div>';
			}
		}
		?>
<form action="" method="POST">

                                    <div class="control-group">
                                       <div class="controls">
                                       <label class="control-label">Mot de passe actuel</label>
                                          <input type="password" name="cpassword" class="m-wrap small" />
                                       </div>
                                    </div>
                                    <div class="control-group">
                                       <div class="controls">
                                       <label class="control-label">Nouveau mot de passe</label>
                                          <input type="password" name="npassword" class="m-wrap small" />
                                       </div>
                                    </div>
                                    <div class="control-group">
                                       <div class="controls">
                                       <label class="control-label">Répéter le mot de passe</label>
                                          <input type="password" name="rpassword" class="m-wrap small" />
                                       </div>
                                    </div><br>
<input type="submit" style="margin-left:16px;" value="Modifier" name="updatePassBtn" class="btn green" />
</form>
										</div>