hash

(PHP 5 >= 5.1.2, PECL hash >= 1.1)

hash — Generate a hash value (message digest)

Beschreibung

string hash ( string $algo , string $data [, bool $raw_output = false ] )

Parameter-Liste

algo: Name of selected hashing algorithm (i.e. "md5", "sha256", "haval160,4", etc..)
data: Message to be hashed.
raw_output: When set to TRUE, outputs raw binary data. Default value (FALSE) outputs lowercase hexits.

Rückgabewerte

Returns a string containing the calculated message digest as lowercase hexits unless raw_output is set to true in which case the raw binary representation of the message digest is returned.

Beispiele

Beispiel #1 A hash() example


<?php
echo hash('ripemd160', 'The quick brown fox jumped over the lazy dog.');
?>

Das oben gezeigte Beispiel erzeugt folgende Ausgabe:

ec457d0a974c48d5685a7efa03d137dc8bbde7e3

Siehe auch

hash_file() - Generate a hash value using the contents of a given file
hash_hmac() - Generate a keyed hash value using the HMAC method
hash_init() - Initialize an incremental hashing context
md5() - Errechnet den MD5-Hash eines Strings
sha1() - Berechnet den SHA1-Hash eines Strings

Mcrypt

hash_update

Last updated: Fri, 30 Oct 2009

add a note User Contributed Notes
hash

Kai Petzke
16-Oct-2009 12:14


The well known hash functions MD5 and SHA1 should be avoided in new applications. Collission attacks against MD5 are well documented in the cryptographics literature and have already been demonstrated in practice. Therefore, MD5 is no longer secure for certain applications.



Collission attacks against SHA1 have also been published, though they still require computing power, which is somewhat out of scope. As computing power increases with time and the attacks are likely to get better, too, attacks against systems relying on SHA1 for security are likely to become feasible within the next few years.



There is no lack of potential alternative hash algorithms, as the many choices for the "algo" argument of PHPs hash() function already suggests. Unfortunately, there is lack of analysis, as to how secure these alternative algorithms are. It is rather safe to assume, though, that the SHA2 family with its most prominent members SHA-256 und SHA-512, is better than SHA1.



When storing password hashes, it is a good idea to prefix a salt to the password before hashing, to avoid the same passwords to hash to the same values and to avoid the use of rainbow tables for password recovery. Unlike suggested in other articles, there is no security advantage in putting the salt in the middle, or even at both the beginning and the end, of the combined salt-password-string.



Rather, there are two other factors, that determine the strength of the salt: Its length and its variability. For example, using the same salt for all passwords is easy to implement, but gives only very little additional security. In particular, if users type the same passwords, they will still hash to the same value!



Therefore, the salt should be random string with at least as many variable bits, as there are bits in the hash result. In the user database, store username, the randomly generated salt for that user, and the result of hashing the salt-password-string. Access authentication is then done by looking up the entry for the user, calculating the hash of the salt found in the database and the password provided by the user, and comparing the result with the one stored in the database.

luka8088 at gmail dot com
14-Mar-2009 11:20


Performance test results on my laptop:

Results are here shorten to fit php web notes ...

This was tested with 1024000 bytes (1000 KB) of random data, md4 always gets the first place, and md2 always get the last place :)



Results: (in microseconds)

   1.  md4                           5307.912

   2.  md5                           6890.058

   3.  crc32b                        7298.946

   4.  crc32                         7561.922

   5.  sha1                          8886.098

   6.  tiger128,3                    11054.992

   7.  haval192,3                    11132.955

   8.  haval224,3                    11160.135

   9.  tiger160,3                    11162.996

  10.  haval160,3                    11242.151

  11.  haval256,3                    11327.981

  12.  tiger192,3                    11630.058

  13.  haval128,3                    11880.874

  14.  tiger192,4                    14776.945

  15.  tiger128,4                    14871.12

  16.  tiger160,4                    14946.937

  17.  haval160,4                    15661.954

  18.  haval192,4                    15717.029

  19.  haval256,4                    15759.944

  20.  adler32                       15796.184

  21.  haval128,4                    15887.022

  22.  haval224,4                    16047.954

  23.  ripemd256                     16245.126

  24.  haval160,5                    17818.927

  25.  haval128,5                    17887.115

  26.  haval224,5                    18085.002

  27.  haval192,5                    18135.07

  28.  haval256,5                    18678.903

  29.  sha256                        19020.08

  30.  ripemd128                     20671.844

  31.  ripemd160                     21853.923

  32.  ripemd320                     22425.889

  33.  sha384                        45102.119

  34.  sha512                        45655.965

  35.  gost                          57237.148

  36.  whirlpool                     64682.96

  37.  snefru                        80352.783

  38.  md2                           705397.844



Code for generating this:

(compatible both with browser and cli mode)



<pre>



<?php



echo 'Building random data ...' . PHP_EOL; 

@ob_flush();flush();



$data = '';

for ($i = 0; $i < 64000; $i++)

    $data .= hash('md5', rand(), true);



echo strlen($data) . ' bytes of random data built !' . PHP_EOL . PHP_EOL . 'Testing hash algorithms ...' . PHP_EOL; 

@ob_flush();flush();



$results = array();

foreach (hash_algos() as $v) {

    echo $v . PHP_EOL; 

    @ob_flush();flush();

    $time = microtime(true);

    hash($v, $data, false);

    $time = microtime(true) - $time;

    $results[$time * 1000000000][] = "$v (hex)";

    $time = microtime(true);

    hash($v, $data, true);

    $time = microtime(true) - $time;

    $results[$time * 1000000000][] = "$v (raw)";

}



ksort($results);



echo PHP_EOL . PHP_EOL . 'Results: ' . PHP_EOL; 



$i = 1;

foreach ($results as $k => $v)

    foreach ($v as $k1 => $v1)

        echo ' ' . str_pad($i++ . '.', 4, ' ', STR_PAD_LEFT) . '  ' . str_pad($v1, 30, ' ') . ($k / 1000) . ' microseconds' . PHP_EOL;



?>



</pre>

kevin at bionichippo dot com
14-Mar-2009 08:06


When using hash() for storing passwords, I've found that the best practice is not to use just one salt, but two. This example uses my preferred algorithm for passwords, whirlpool.





This way, even if someone can produce a rainbow table for your algorithm, and has the salt to do it with, they will never know where in the hash parameter the second salt was placed, because they don't know the length of the actual password.








<?php





function doubleSalt($toHash,$username){


$password = str_split($toHash,(strlen($toHash)/2)+1);


var_dump($password);


$hash = hash('md5', $username.$password[0].'centerSalt'.$password[1]);


return $hash;


}





?>





The str_split operation needs a +1 appended, otherwise the last character is cut off when the password is an odd number of characters, so that pass1 and pass2 will return the same value.





[NOTE BY danbrown AT php DOT net: Bug spotted by (Sunil) on 13-Mar-2009 and fix applied by OP.]

Leigh
06-Aug-2008 05:10


Just a quick note about these benchmarks and how you should apply them.



If you are hashing passwords etc for security, speed is not your friend. You should use the slowest method.



Slow to hash means slow to crack and will hopefully make generating things like rainbow tables more trouble than it's worth.

The
27-May-2008 10:52


Note that some of the hash algorithms provided are considered weak (e.g., md5, sha1 and haval128,3). If you have a choice in the matter, use ripemd160, whirlpool or tiger192,4.

inspiration3 at gmail dot com
04-May-2008 03:12


Another comprehensive benchmark script that orders results from best to worst and includes the crc32(), md5() and sha1() standalone functions:



<?php



define('HASH_TIMES', 1000);

define('HASH_DATA', 'The quick brown fox jumped over!'); // 32 bytes



header('Content-Type: text/plain');

echo 'Testing ' . strlen(HASH_DATA) . ' bytes of data over ' . HASH_TIMES . " iterations:\n";



foreach (hash_algos() as $algo) {

    $time = microtime(1);

    for ($i = 0; $i < HASH_TIMES; $i++) hash($algo, HASH_DATA);

    $results[$algo] = microtime(1) - $time;

}



$time = microtime(1); for ($i = 0; $i < HASH_TIMES; $i++) crc32(HASH_DATA); $results['crc32()'] = microtime(1) - $time;

$time = microtime(1); for ($i = 0; $i < HASH_TIMES; $i++) md5(HASH_DATA); $results['md5()'] = microtime(1) - $time;

$time = microtime(1); for ($i = 0; $i < HASH_TIMES; $i++) sha1(HASH_DATA); $results['sha1()'] = microtime(1) - $time;



asort($results, SORT_NUMERIC);

foreach ($results as $algo => $time) echo "\n$time\t$algo";



?>

Marcus
27-Apr-2008 12:15


A upgrade of (dani88elx AT gmail DOT com)'s performance test [from 26-Jun-2007], this time grading them by speed (fastest first) and comparing times between hex and raw data.





<?php


function testAlgos() {


$algos = hash_algos();


$word="This will be crypted by all different algoritms";


$results = array();


foreach($algos as $algo)


{


    $time=microtime(1);


    $data = hash($algo, $word, false);


    $results["".(microtime(1)-$time)][] = "$algo (hex)";


}


foreach($algos as $algo)


{


    $time=microtime(1);


    $data = hash($algo, $word, true);


    $results["".(microtime(1)-$time)][] = "$algo (raw)";


}


ksort($results);


foreach($results as $time => &$algos) {


    echo $time."\n";


    sort($algos);


    foreach($algos as $algo)


        echo "\t".$algo."\n";


}


}


testAlgos();


?>

mikael at webhost3 dot eu
10-Mar-2007 01:34


<?php

$time=microtime(1);

for ($i=0;$i<100000;$i++)

   hash('md5', 'string');

echo microtime(1)-$time,': hash/md5<br>';



$time=microtime(1);

for ($i=0;$i<100000;$i++)

   md5('string');

echo microtime(1)-$time,': md5<br>';



$time=microtime(1);

for ($i=0;$i<100000;$i++)

   hash('sha1', 'string');

echo microtime(1)-$time,': hash/sha1<br>';



$time=microtime(1);

for ($i=0;$i<100000;$i++)

   sha1('string');

echo microtime(1)-$time,': sha1<br>';

?>------------------------<br><?php

$time=microtime(1);

for ($i=0;$i<100000;$i++)

   hash('md5', $i);

echo microtime(1)-$time,': hash/md5<br>';



$time=microtime(1);

for ($i=0;$i<100000;$i++)

   md5($i);

echo microtime(1)-$time,': md5<br>';



$time=microtime(1);

for ($i=0;$i<100000;$i++)

   hash('sha1', $i);

echo microtime(1)-$time,': hash/sha1<br>';



$time=microtime(1);

for ($i=0;$i<100000;$i++)

   sha1($i);

echo microtime(1)-$time,': sha1<br>';

?>

Gives:

0.33311605453491: hash/md5

1.0671429634094: md5

0.383131980896: hash/sha1

1.3252220153809: sha1

------------------------

0.37684988975525: hash/md5

1.1258299350739: md5

0.43960785865784: hash/sha1

1.3876020908356: sha1

add a note

Mcrypt

hash_update

Last updated: Fri, 30 Oct 2009