password_get_info
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.
password_hash
(PHP 5 >= 5.5.0)
password_hash — Creates 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.
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 theCRYPT_BLOWFISHalgorithm 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, orFALSEon 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 ommitted, 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.
-
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.
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:
$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:
$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(22, MCRYPT_DEV_URANDOM),
];
echo password_hash("rasmuslerdorf", PASSWORD_BCRYPT, $options)."\n";
?>
The above example will output:
$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:
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
- password_verify() - Verifies that a password matches a hash
- crypt() - One-way string hashing
- » userland implementation
add a note
User Contributed Notes
password_hash - [5 notes]
chris at acsdi dot com ¶
10 days ago
lekensteyn at gmail dot com ¶
6 months ago
The length of the hash returned by password_hash() for for PASSWORD_BCRYPT is 60 chars.
martinstoeckli ¶
6 months 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
martinstoeckli ¶
3 months 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.
Alan ¶
11 days ago
Fyi, I ran into an issue when not providing the salt to crypt() which coincides with the documentation on the crypt() page: "If not provided, the behavior is defined by the algorithm implementation and can lead to unexpected results." Encrypting text on a windows platform could not be decrypted on a linux platform because the default algorithms were different. I had to specifically provide a salt to ensure the same algorithm was used on both platforms. I would imagine this would occur with password_hash() as well.