uso intensivo di mcrypt e conseguenze sulle prestazioni

[Ratatuia]

ciao a tutti,
di recente mi sono trovato ad usare intensivamente mcrypt in un certo punto di un applicativo dove ho necessità di criptare e decriptare le informazioni sulla carta di credito dei clienti...
il problema principale è che su frequenti richieste sembra che php non regga molto (quando alla fine i dati sarebbero pochi) e la generazione dell'output arriva a tempi decisamente non accettabili (dai 3 secondi ai 30 secondi). Allo stesso tempo, a volte l'output viene generato istantamente, considerando che a parte decriptare i dati nel database non deve fare altro...

il codice incriminato è questo

class CreditCard extends mysql
{
    private $ccId;
    private $ccOwner;
    private $ccType;
    private $ccNumber;
    private $ccExpDate;
    private $encrypted = 0;
    private $cipher;
    private $keyString;
    private $iv;
    
    public function __construct($id=0,$details = 0)
    {
        parent::__construct();
        $this->ccId = $id;
        if ($this->ccId != 0)
            $this->getCcData($details);
    }
    
    public function getCcData($details)
    {
        $fields = ($details)?"*":"cc_type";
        $data = mysql_fetch_assoc($this->db_query("SELECT ".$fields." FROM thebox_customers_cc WHERE cc_id = '".$this->ccId."'"));
        if ($details)
        {
            $this->ccOperationsInit();
            $this->ccOwner = $data["cc_owner"];
            $this->ccNumber = $data["cc_number"];
            $this->ccExpDate = $data["cc_exp_date"];
        }
        $this->ccType = $data["cc_type"];
    }
    
    public function getExpDate($how = 0)
    {
        if ($how == 0)
        {
            $date = split("-",$this->ccExpDate);
            return $date[1]."/".$date[0];
        }
        else
            return $this->ccExpDate; 
    }
    
    public function getCcType()
    {
        return $this->ccType;
    }
    
    public function ccOperationsInit()
    {
        $this->keyString = "unastringamoltolunga";
        $size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_ECB);
        $this->iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM);
        $this->cipher = mcrypt_module_open(MCRYPT_BLOWFISH,'','ecb','');
    }
    
    public function getDecryptedField($field)
    {
        mcrypt_generic_init($this->cipher, $this->keyString, $this->iv);
        $tmp = mdecrypt_generic($this->cipher,base64_decode($this->$field));
        $tmp = addcslashes($tmp, "\0..\37!@\177..\377");
        $tmp = str_replace("\\000","",$tmp);
        mcrypt_generic_deinit($this->cipher);
        return $tmp;
    }
    
    public function getEncryptedField($field)
    {
        mcrypt_generic_init($this->cipher, $this->keyString, $this->iv);
        $tmp = base64_encode(mcrypt_generic($this->cipher,$this->$field));
        mcrypt_generic_deinit($this->cipher);
        return $tmp;
    }
    
    public function saveCcData($customerId,$ccOwner,$ccType,$ccNumber,$ccDate)
    {
        $this->ccOwner = $ccOwner;
        $this->ccType = $ccType;
        $this->ccNumber = $ccNumber;
        $this->ccExpDate = $ccDate . "-01";
        
        $query_cc = "INSERT INTO 
        thebox_customers_cc 
        VALUES 
        ('',
        '".$customerId."',
        '".$this->getEncryptedField("ccOwner")."',
        '".$this->ccType."',
        '".$this->getEncryptedField("ccNumber")."',
        '".$this->ccExpDate."')";
        $this->db_query($query_cc,1);
        $this->ccId = mysql_insert_id();
    }
    
    # getters specifici v0.2
    public function id() {
        return $this->ccId;
    }
    
    public function encryptedOwner() {
        return $this->ccOwner;
    }
    
    public function owner() {
        mcrypt_generic_init($this->cipher, $this->keyString, $this->iv);
        return mdecrypt_generic($this->cipher,base64_decode($this->ccOwner));
    }
    
    public function type() {
        return $this->ccType;
    }
    
    public function encryptedNumber() {
        return $this->ccNumber;
    }
    
    public function unshadowNumber() {
        mcrypt_generic_init($this->cipher, $this->keyString, $this->iv);
        return mdecrypt_generic($this->cipher,base64_decode($this->ccNumber));
    }
    
    public function number() {
        mcrypt_generic_init($this->cipher, $this->keyString, $this->iv);
        $unshadow = mdecrypt_generic($this->cipher,base64_decode($this->ccNumber));
        return "**** **** **** ".substr($unshadow,-4);
    }
    
    public function expiration() {
        list($y,$m) = explode('-',substr($this->ccExpDate,0,7));
        return "$m/$y";
    }
} 

qualche suggerimento?