RSA encryption & decryption

var RSA = {
    getPublicKey: function($pem) {
        if ($pem.length < 50)
            return false;
        if ($pem.substr(0, 26) != "-----BEGIN PUBLIC KEY-----")
            return false;
        $pem = $pem.substr(26);
        if ($pem.substr($pem.length - 24) != "-----END PUBLIC KEY-----")
            return false;
        $pem = $pem.substr(0, $pem.length - 24);
        $pem = new ASN1Data(Base64.decode($pem));
        if ($pem.error)
            return false;
        $pem = $pem.data;
        if ($pem[0][0][0] == "1.2.840.113549.1.1.1")
            return new RSAPublicKey($pem[0][1][0][0], $pem[0][1][0][1]);
        return false;
    },
    encrypt: function($data, $pubkey) {
        if (!$pubkey)
            return false;
        var bytes = ($pubkey.modulus.bitLength() + 7) >> 3;
        $data = this.pkcs1pad2($data, bytes);
        if (!$data)
            return false;
        $data = $data.modPowInt($pubkey.encryptionExponent, $pubkey.modulus);
        if (!$data)
            return false;
        $data = $data.toString(16);
        while ($data.length < bytes * 2)
            $data = '0' + $data;
        return Base64.encode(Hex.decode($data));
    },
    decrypt: function($text, $pubkey)
    {
        if (!$pubkey)
            return false;
        $text = Hex.encode(Base64.decode($text)).toString(16);
        while ($text[0] == '0')
            $text = $text.replace('0', '');
        $text = new BigInteger($text, 16);
        $text = $text.modPowInt($pubkey.encryptionExponent, $pubkey.modulus);
        if (!$text)
            return false;
        var bytes = ($pubkey.modulus.bitLength() + 7) >> 3;
        $text = this.pkcs1unpad2($text, bytes);

        return $text;
    },
    pkcs1pad2: function pkcs1pad2(s, n) {
        if (n < s.length + 11) { // TODO: fix for utf-8
            alert("Message too long for RSA");
            return null;
        }
        var ba = new Array();
        var i = s.length - 1;
        while (i >= 0 && n > 0) {
            var c = s.charCodeAt(i--);
            if (c < 128) { // encode using utf-8
                ba[--n] = c;
            }
            else if ((c > 127) && (c < 2048)) {
                ba[--n] = (c & 63) | 128;
                ba[--n] = (c >> 6) | 192;
            }
            else {
                ba[--n] = (c & 63) | 128;
                ba[--n] = ((c >> 6) & 63) | 128;
                ba[--n] = (c >> 12) | 224;
            }
        }
        ba[--n] = 0;
        var rng = new SecureRandom();
        var x = new Array();
        while (n > 2) { // random non-zero pad
            x[0] = 0;
            while (x[0] == 0)
                rng.nextBytes(x);
            ba[--n] = x[0];
        }
        ba[--n] = 2;
        ba[--n] = 0;
        return new BigInteger(ba);
    },
    pkcs1unpad2: function pkcs1unpad2(d, n)
    {
        var b = d.toByteArray();
        var i = 0;
        while (i < b.length && b[i] == 0)
            ++i;
        /*if (b.length - i != n - 1 || b[i] != 2)
         return null;*/
        ++i;
        while (b[i] != 0)
            if (++i >= b.length)
                return null;
        var ret = "";
        while (++i < b.length) {
            var c = b[i] & 255;
            if (c < 128) { // utf-8 decode
                ret += String.fromCharCode(c);
            }
            else if ((c > 191) && (c < 224)) {
                ret += String.fromCharCode(((c & 31) << 6) | (b[i + 1] & 63));
                ++i;
            }
            else {
                ret += String.fromCharCode(((c & 15) << 12) | ((b[i + 1] & 63) << 6) | (b[i + 2] & 63));
                i += 2;
            }
        }
        return ret;
    }
}