How to Generate HMAC SHA256 in PHP?

I've coded a token generation routine in C#, that I need to convert to PHP and am having trouble.

The C# code is:
        public string GenerateToken(string username, string password, string ip, string userAgent, long ticks)
            authSettings setting = getSettings();
            string hash = string.Join(":", new string[] { username, ip, userAgent, ticks.ToString() });
            string hashLeft = "";
            string hashRight = "";
            using (HMAC hmac = HMACSHA256.Create(setting.alg))
                hmac.Key = Encoding.UTF8.GetBytes(GetHashedPassword(password,setting));
                hashLeft = Convert.ToBase64String(hmac.Hash);
                hashRight = string.Join(":", new string[] { username, ticks.ToString() });
            string genToken = Convert.ToBase64String(Encoding.UTF8.GetBytes(string.Join(":", hashLeft, hashRight)));
            return genToken;

        public string GetHashedPassword(string password, authSettings setting)
            string key = string.Join(":", new string[] { password, setting.salt });
            using (HMAC hmac = HMACSHA256.Create(setting.alg))
                hmac.Key = Encoding.UTF8.GetBytes(setting.salt);
                return Convert.ToBase64String(hmac.Hash);

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and the PHP code I have is:
//Define key to hash, password + salt
$key = base64_encode(hash_hmac('sha256', utf8_encode($password . ':' . $salt), utf8_encode($salt)));
echo '<b>Key:</b> ' . $key . '<br>';

//Define Message
$message = $username . ':' . $ip . ':' . $agent . ':' . $timestamp;

//Create Hash
$hash = hash_hmac('sha256', $message, $key);

//Create token
$token = base64_encode($hash);

$tokenId = $username . ':' . $timestamp;
$tokenString = $token . ':' . $tokenId;
$tokenRetVal = base64_encode($tokenString);

echo '<b>Token String:</b> ' . $tokenString . '<br>';
echo '<b><font color=red>Token:</font></b> ' . $tokenRetVal . '<br>';

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The results of the idential values, are completely different.  What am I doing wrong?
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gr8gonzoConnect With a Mentor ConsultantCommented:
Also, I'd recommend trying to set up your PHP code to more closely match the C# code. Something like this:

echo GenerateToken("Bob","secret","","Intranet Exploder",123456890);

function getSettings()
	return array("salt" => "abc");

function GenerateToken($username, $password, $ip, $userAgent, $ticks)
	$setting = getSettings();
  $hash = implode(":",array($username,$ip,$userAgent,$ticks));
  $hashLeft = "";
  $hashRight = "";
  	$hmacKey = GetHashedPassword($password,$setting);
  	$hmacComputedHash = hash_hmac('sha256', $hash, $hmacKey, true);
  	$hashLeft = base64_encode($hmacComputedHash);
  	$hashRight = implode(":",array($username,$ticks));
  $genToken = base64_encode(implode(":",array($hashLeft,$hashRight)));
  return $genToken;

function GetHashedPassword($password, $setting)
	$key = implode(":",array($password,$setting["salt"]));
	  $hmacKey = $setting["salt"];
	  $hmacComputedHash = hash_hmac('sha256', $key, $hmacKey, true);
	  return base64_encode($hmacComputedHash);

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Phil DavidsonCommented:
Wouldn't the different salt values make the results different?  Are the relevant keys exactly the same?  If the servers are different for the C# version vs the PHP version, they may use different keys to begin with.
adworldmediaCTOAuthor Commented:
The salt is the same in both implementations.  And the server running the c# is Windows and the PHP one is Linux.
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Phil DavidsonCommented:
Isn't the hash the result of a RSA or SHA key on the server?   Maybe it is over my head.  It seems like different servers would have different private keys and thus generate different hash values.
You're probably double-encoding your UTF-8 characters.

Encoding.UTF8.GetBytes() isn't encoding the string to UTF-8 - it is simply returning the byte array that represents that string that is presumably already UTF-8 encoded.

However, in PHP, utf8_encode() assumes that the source string is in an ISO-8859-1 format (see my article on this - and will convert any characters that fall outside the normal ASCII range to their UTF-8 equivalents. So if your source string is already encoded as UTF-8 and contains such characters, then you are actually corrupting your string (which would, of course, lead to a different result).

I would suggest taking out the utf8_encode() calls altogether in PHP, assuming that your source values are already encoded.

Or if you just want to do a simple test to confirm this is the problem, use a simple plain ASCII string (alphanumeric characters only) for your key/salt on both sides and then test.

Also, double-check and compare your timestamp and ticks. Ticks in C# are different than the timestamp in PHP (I can't see where the $timestamp value comes from).

Oh, and finally, hash_hmac() will return a hex-encoded hash UNLESS you specify "true" as the 4th parameter. Adding that "true" parameter will result in you getting the raw bytes, which is what you get in C#. So that's another possible place where the differences could occur.
adworldmediaCTOAuthor Commented:
This worked perfectly!  Thanks!!
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