Validate a string using pack('H*') - php

Question

I'm working on an encrypted database... I have been using m_crypt functions.. I have sucessfully got my method of encryption/decryption.. But a problem lies with creating my OO class to serve this function.. I have the following:
class Encryption {
public function __construct($Hex = null){
if (isset($Hex)){
if (ctype_xdigit($Hex)){
echo "Is Hex";
}
if (preg_match('~^[01]+$~', $Hex)) {
echo "Is Binary";
}
}
}
}
$key = pack('H*', "bcb04b7e103a0cd8b54763051cef08bc55abe029fdebae5e1d417e2ffb2a00a3");
$Class_OO = new Encryption($key);
The echos are for testing purposes.. But I want to validate this as a valid hexidecimal/binary or the datatype this string is.
performing:
print_r($key);
Returns the following:
¼°K~:صGcï¼U«à)ýë®^A~/û*£
But what datatype is this? On the documentation: http://www.php.net/manual/en/function.mcrypt-encrypt.php The line is presented:
convert a string into a key
key is specified using hexadecimal
So my question is what datatype is this? I understand this is in the ASCII range, but that is as far as my knowledge goes.. Furthermore, a successful answer for this will also assist me in creating another key which is not the one specified by the actual documentation

Answer 1

Your $key is the return value from pack, which in this case is a binary string (essentially raw binary values). See the first line in the documentation for the pack() function return value: http://php.net/manual/en/function.pack.php
Pack given arguments into binary string [emphasis added] according to format.
You would normally base64 encode a binary string before attempting any kind of output, because by definition, a binary string may (and often does) include non-printable characters, or worse - terminal control/escape sequences which can hose up your screen.
Think of it like printing a raw Word or Excel file: you'll probably see recognizable values (although in this case occasional alpha-numerics), but lots of garbage too.
Base64 encoding is a technique to inspect these strings in a safe way.
But what your question implies is that you are very much entering this territory new. You should probably take a look at the Matasano crypto tutorial here: http://www.matasano.com/articles/crypto-challenges/. It is an excellent starting point, and completing exercise #1 in it (maybe 20 minutes of work) will shed complete light on your question above.

Answer 2

In response to your question.. The only viable viable datatype this is submitted in is a string. As you said in your comment:
I have figured using the IV functions of mcrypt then using bin2hex,
using this in the second param of the pack function seems to work
without a fail.. BUT, my overall question is how to validate:
¼°K~:صGcï¼U«à)ýë®^A~/û*£ down to a specific datatype
You have answered how to create an acceptable format for the pack('H*') but as far as validation goes:
if (is_string($Var)){
}
Is the way to go, as this is how it's submitted. It's not a bool, hex, binary, int.. So the only valid method of validating is to validate it as a string.