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PHP : Function Reference : Mhash Functions : mhash


Compute hash (PHP 4, PHP 5)
string mhash ( int hash, string data [, string key] )

Code Examples / Notes » mhash


Want to Create a md5 HMAC, but don't have hmash installed?
Use this:
function hmac ($key, $data)
   // RFC 2104 HMAC implementation for php.
   // Creates an md5 HMAC.
   // Eliminates the need to install mhash to compute a HMAC
   // Hacked by Lance Rushing
   $b = 64; // byte length for md5
   if (strlen($key) > $b) {
       $key = pack("H*",md5($key));
   $key  = str_pad($key, $b, chr(0x00));
   $ipad = str_pad('', $b, chr(0x36));
   $opad = str_pad('', $b, chr(0x5c));
   $k_ipad = $key ^ $ipad ;
   $k_opad = $key ^ $opad;
   return md5($k_opad  . pack("H*",md5($k_ipad . $data)));
To test:
Run this on a server _with_ mhash installed:
$key = 'Jefe';
$data = "what do ya want for nothing?";
echo hmac($key, $data);
echo "<br>\n";
echo bin2hex (mhash(MHASH_MD5, $data, $key));
should produce:
Happy hashing.

02-may-2001 09:02

Using RedHat 7.1, after compile/install, I had to add the line
to /etc/ and run ldconfig to make this work.


This confused me a bit when I first read the documetation for mhash. The functions that accept a hash accept them as an INTEGER not a STRING. In this case, MHASH_MD5 = 1. It is a constant, not a string.
Just thought I'd point that out, so if anyone is confused they can read that. That's the use of mhash_get_hash_name(). You input the constant (which is an integer) and it returns the hash name.


Thanks a lot to Lance for showing how to create mhash without installing the perl extension for mhash.
I have been asking my webhosting administrator to recompile Perl with mhash extension, but do not want to do it. As a result, our company can't get credit card authorization because they require fingerprint which uses the function mhash. Now, it's working fine.
Thanks a lot, Lance.....


password security:
when you hash passwords to save them in cookie , url ,etc' my sugsession is to hash them with date
becouse of evry body can view server log or any other loged info and reuse the hash
ie.: to re call a url eg. admin.php?user=root&passhash=5rft346tert
in this example the password keepped in secret but what stopping me to reuse the url
hash("secret") // bad security
hash("secret".date("Ymg")) // better security
// the hash good only for today


Netscape messaging / directory server 4+ uses SHA-1
to store password in the ldap database (slapd).
The password is first SHA-1 hashed then base64 encoded:
$pwd = "secret";
$hash = "{SHA}".base64_encode( mHash(MHASH_SHA1, $pwd));
echo "Hash: ". $hash ;


Many digest algorithms (especially MD5) are less secure if you are hashing data that is smaller than the algorithm's output.  I recommend either hashing a secret key/salt with the original data to increase it's security.


Just in case you did not observe, the function of Lance is independent of hash fuction used to get HMAC , so if one use sha1() function from php instead md5() will get sha1 HMAC.
Just try .
Thanks again Lance

jerry d0t wilborn

in responce to lance's post:
the function comes back with a hex representation of the hmac, if you wish to convert to what mhash returns natively (binary) use:  pack("H*", hmac(variables...));


If you are going to use only MD5 sums, it would be a good idea to use the internal's PHP function md5() ir order to avoid the library dependence.


Don't forget php has two built in hashing algorithms:
md5(), and sha1()
So if you are using: mhash(MHASH_MD5, $str) or mhash(MHASH_SHA1, $str) you could use md5($str) or sha1($str).
** But remember that md5() and sha1() produce HEX output while mhash() produces a BIN output.  So:
md5($str) == bin2hex(mhash(MHASH_MD5, $str))
sha1($str) == bin2hex(mhash(MHASH_SHA1, $str))
pack("H*", md5($str)) == mhash(MHASH_MD5, $str)
pack("H*", sha1($str)) == mhash(MHASH_SHA1, $str)
(Just remember to pack() or bin2hex() your output to get the output you need)


pack("H*", md5($str)) == mhash(MHASH_MD5, $str)
pack("H*", sha1($str)) == mhash(MHASH_SHA1, $str)
That's an awfully inefficient way of doing things. You can just put ", true" after md5 or sha1 to get binary output instead of having it convert it to hex then back.
Easier way:
md5($str, true) == mhash(MHASH_MD5, $str)
sha1($str, true) == mhash(MHASH_SHA1, $str)

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