PHP 5.6.0beta1 released

password_hash

(PHP 5 >= 5.5.0)

password_hashCreates a password hash

Description

string password_hash ( string $password , integer $algo [, array $options ] )

password_hash() creates a new password hash using a strong one-way hashing algorithm. password_hash() is compatible with crypt(). Therefore, password hashes created by crypt() can be used with password_hash().

The following algorithms are currently supported:

  • PASSWORD_DEFAULT - Use the bcrypt algorithm (default as of PHP 5.5.0). Note that this constant is designed to change over time as new and stronger algorithms are added to PHP. For that reason, the length of the result from using this identifier can change over time. Therefore, it is recommended to store the result in a database column that can expand beyond 60 characters (255 characters would be a good choice).
  • PASSWORD_BCRYPT - Use the CRYPT_BLOWFISH algorithm to create the hash. This will produce a standard crypt() compatible hash using the "$2y$" identifier. The result will always be a 60 character string, or FALSE on failure.

    Supported Options:

    • salt - to manually provide a salt to use when hashing the password. Note that this will override and prevent a salt from being automatically generated.

      If omitted, a random salt will be generated by password_hash() for each password hashed. This is the intended mode of operation.

    • cost - which denotes the algorithmic cost that should be used. Examples of these values can be found on the crypt() page.

      If omitted, a default value of 10 will be used. This is a good baseline cost, but you may want to consider increasing it depending on your hardware.

Parameters

password

The user's password.

Caution

Using the PASSWORD_BCRYPT for the algo parameter, will result in the password parameter being truncated to a maximum length of 72 characters. This is only a concern if are using the same salt to hash strings with this algorithm that are over 72 bytes in length, as this will result in those hashes being identical.

algo

A password algorithm constant denoting the algorithm to use when hashing the password.

options

An associative array containing options. See the password algorithm constants for documentation on the supported options for each algorithm.

If omitted, a random salt will be created and the default cost will be used.

Return Values

Returns the hashed password, or FALSE on failure.

The used algorithm, cost and salt are returned as part of the hash. Therefore, all information that's needed to verify the hash is included in it. This allows the password_verify() function to verify the hash without needing separate storage for the salt or algorithm information.

Examples

Example #1 password_hash() example

<?php
/**
 * We just want to hash our password using the current DEFAULT algorithm.
 * This is presently BCRYPT, and will produce a 60 character result.
 *
 * Beware that DEFAULT may change over time, so you would want to prepare
 * By allowing your storage to expand past 60 characters (255 would be good)
 */
echo password_hash("rasmuslerdorf"PASSWORD_DEFAULT)."\n";
?>

The above example will output something similar to:

$2y$10$.vGA1O9wmRjrwAVXD98HNOgsNpDczlqm3Jq7KnEd1rVAGv3Fykk1a

Example #2 password_hash() example setting cost manually

<?php
/**
 * In this case, we want to increase the default cost for BCRYPT to 12.
 * Note that we also switched to BCRYPT, which will always be 60 characters.
 */
$options = [
    
'cost' => 12,
];
echo 
password_hash("rasmuslerdorf"PASSWORD_BCRYPT$options)."\n";
?>

The above example will output something similar to:

$2y$12$QjSH496pcT5CEbzjD/vtVeH03tfHKFy36d4J0Ltp3lRtee9HDxY3K

Example #3 password_hash() example setting salt manually

<?php
/**
 * Note that the salt here is randomly generated.
 * Never use a static salt or one that is not randomly generated.
 *
 * For the VAST majority of use-cases, let password_hash generate the salt randomly for you
 */
$options = [
    
'cost' => 11,
    
'salt' => mcrypt_create_iv(22MCRYPT_DEV_URANDOM),
];
echo 
password_hash("rasmuslerdorf"PASSWORD_BCRYPT$options)."\n";
?>

The above example will output something similar to:

$2y$11$q5MkhSBtlsJcNEVsYh64a.aCluzHnGog7TQAKVmQwO9C8xb.t89F.

Example #4 password_hash() example finding a good cost

<?php
/**
 * This code will benchmark your server to determine how high of a cost you can
 * afford. You want to set the highest cost that you can without slowing down
 * you server too much. 10 is a good baseline, and more is good if your servers
 * are fast enough.
 */
$timeTarget 0.2

$cost 9;
do {
    
$cost++;
    
$start microtime(true);
    
password_hash("test"PASSWORD_BCRYPT, ["cost" => $cost]);
    
$end microtime(true);
} while ((
$end $start) < $timeTarget);

echo 
"Appropriate Cost Found: " $cost "\n";
?>

The above example will output something similar to:

Appropriate Cost Found: 11

Notes

Caution

It is strongly recommended that you do not generate your own salt for this function. It will create a secure salt automatically for you if you do not specify one.

Note:

It is recommended that you should test this function on your servers, and adjust the cost parameter so that execution of the function takes approximately 0.1 to 0.5 seconds. The script in the above example will help you choose a good cost value for your hardware.

Note: Updates to supported algorithms by this function (or changes to the default one) must follow the follwoing rules:

  • Any new algorithm must be in core for at least 1 full release of PHP prior to becoming default. So if, for example, a new algorithm is added in 5.5.5, it would not be eligible for default until 5.7 (since 5.6 would be the first full release). But if a different algorithm was added in 5.6.0, it would also be eligible for default at 5.7.0.
  • The default should only change on a full release (5.6.0, 6.0.0, etc) and not on a revision release. The only exception to this is in an emergency when a critical security flaw is found in the current default.

See Also

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User Contributed Notes 8 notes

up
52
martinstoeckli
1 year ago
There is a compatibility pack available for PHP versions 5.3.7 and later, so you don't have to wait on version 5.5 for using this function. It comes in form of a single php file:
https://github.com/ircmaxell/password_compat
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9
nicoSWD
6 months ago
I agree with martinstoeckli,

don't create your own salts unless you really know what you're doing.

By default, it'll use /dev/urandom to create the salt, which is based on noise from device drivers.

And on Windows, it uses CryptGenRandom().

Both have been around for many years, and are considered secure for cryptography (the former probably more than the latter, though).

Don't try to outsmart these defaults by creating something less secure. Anything that is based on rand(), mt_rand(), uniqid(), or variations of these is *not* good.
up
9
chris at acsdi dot com
9 months ago
Alan is entirely wrong, please ignore his comment and/or vote it down. This method encodes the algorithm and other parameters into the returned hash.

Deliberately specifying the algorithm to use should only be done in a carefully considered scenario, and these functions are designed and policies have been decided to ensure wide compatibility.

The risk of forcing a particular algorithm is that your code will continue to use a weaker algorithm as newer ones are implemented and strengthened.
up
11
Cloxy
5 months ago
You can produce the same hash in php 5.3.7+ with crypt() function:

<?php

$salt
= mcrypt_create_iv(22, MCRYPT_DEV_URANDOM);
$salt = base64_encode($salt);
$salt = str_replace('+', '.', $salt);
$hash = crypt('rasmuslerdorf', '$2y$10$'.$salt.'$');

echo
$hash;

?>
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8
martinstoeckli
1 year ago
In most cases it is best to omit the salt parameter. Without this parameter, the function will generate a cryptographically safe salt, from the random source of the operating system.
up
0
ic dot czech at gmail dot com
29 days ago
@dmp
If you need to generate $2a$ hash you must have php version older than 5.3.7 or use crypt() function instead
<?php
$cost
= 10;
$salt = 'usesomesillystringforsalt';
$hash = crypt('rasmuslerdorf', '$2a$'.$cost.'$'.$salt.'$');
?>
but it's less secured than  $2y$
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0
cottton
1 month ago
if you thought
"why is the salt included in the hash and is it save when i store it as it is in my db?"

Answer i found:
The salt just has to be unique. It not meant to be a secret.

As mentioned in notes and docu before: let password_hash() take care of the salt.

With the unique salt you force the attacker to crack the hash.
The hash is unique and cannot be found at rainbow tables.
up
-2
dmp
1 month ago
How do you use this to generate a $2a$ BCRYPT hash?
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