You would probably have to create a page that loops through the database and updates the fields to encrypt them.
The code might look something like:
<?php require_once('Connections/localhost.php'); ?>
<?php
if (!function_exists("GetSQLValueString")) {
function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "")
{
if (PHP_VERSION < 6) {
$theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;
}
$theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);
switch ($theType) {
case "text":
$theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
break;
case "long":
case "int":
$theValue = ($theValue != "") ? intval($theValue) : "NULL";
break;
case "double":
$theValue = ($theValue != "") ? doubleval($theValue) : "NULL";
break;
case "date":
$theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
break;
case "defined":
$theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;
break;
}
return $theValue;
}
}
mysql_select_db($database_localhost, $localhost);
$query_Recordset1 = "SELECT * FROM myTable ";
$Recordset1 = mysql_query($query_Recordset1, $localhost) or die(mysql_error());
$row_Recordset1 = mysql_fetch_assoc($Recordset1);
$totalRows_Recordset1 = mysql_num_rows($Recordset1);
?>
<?php do { ?>
<?php
$encryptedValue = encryptionFunction($row_Recordset1['ID']);
$query_Recordset1 = "UPDATE myTable SET Password = " . GetSQLValueString($encryptedValue, "text") . " WHERE ID = " . $row_Recordset1['ID'];
?>
<?php } while ($row_Recordset1 = mysql_fetch_assoc($Recordset1)); ?>
<?php
mysql_free_result($Recordset1);
?>
Then you would just view this page once and delete it after. (note: code has a sample encryption function and doesn't include the encryption include file since I didn't know what type of encryption you want to use. The encryption function should be updated before using this code)