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crypt

(PHP 4, PHP 5, PHP 7)

cryptOne-way string hashing

Descrierea

string crypt ( string $str [, string $salt ] )

crypt() will return a hashed string using the standard Unix DES-based algorithm or alternative algorithms that may be available on the system.

The salt parameter is optional. However, crypt() creates a weak password without the salt. PHP 5.6 or later raise an E_NOTICE error without it. Make sure to specify a strong enough salt for better security.

password_hash() uses a strong hash, generates a strong salt, and applies proper rounds automatically. password_hash() is a simple crypt() wrapper and compatible with existing password hashes. Use of password_hash() is encouraged.

Some operating systems support more than one type of hash. In fact, sometimes the standard DES-based algorithm is replaced by an MD5-based algorithm. The hash type is triggered by the salt argument. Prior to 5.3, PHP would determine the available algorithms at install-time based on the system's crypt(). If no salt is provided, PHP will auto-generate either a standard two character (DES) salt, or a twelve character (MD5), depending on the availability of MD5 crypt(). PHP sets a constant named CRYPT_SALT_LENGTH which indicates the longest valid salt allowed by the available hashes.

The standard DES-based crypt() returns the salt as the first two characters of the output. It also only uses the first eight characters of str, so longer strings that start with the same eight characters will generate the same result (when the same salt is used).

On systems where the crypt() function supports multiple hash types, the following constants are set to 0 or 1 depending on whether the given type is available:

Notă:

As of PHP 5.3.0, PHP contains its own implementation and will use that if the system lacks of support for one or more of the algorithms.

Parametri

str

The string to be hashed.

Precauţie

Using the CRYPT_BLOWFISH algorithm, will result in the str parameter being truncated to a maximum length of 72 characters.

salt

An optional salt string to base the hashing on. If not provided, the behaviour is defined by the algorithm implementation and can lead to unexpected results.

Valorile întoarse

Returns the hashed string or a string that is shorter than 13 characters and is guaranteed to differ from the salt on failure.

Avertizare

When validating passwords, a string comparison function that isn't vulnerable to timing attacks should be used to compare the output of crypt() to the previously known hash. PHP 5.6 onwards provides hash_equals() for this purpose.

Istoricul schimbărilor

Versiune Descriere
5.6.5 When the failure string "*0" is given as the salt, "*1" will now be returned for consistency with other crypt implementations. Prior to this version, PHP 5.6 would incorrectly return a DES hash.
5.6.0 Raise E_NOTICE security warning if salt is omitted.
5.5.21 When the failure string "*0" is given as the salt, "*1" will now be returned for consistency with other crypt implementations. Prior to this version, PHP 5.5 (and earlier branches) would incorrectly return a DES hash.
5.3.7 Added $2x$ and $2y$ Blowfish modes to deal with potential high-bit attacks.
5.3.2 Added SHA-256 and SHA-512 crypt based on Ulrich Drepper's » implementation.
5.3.2 Fixed Blowfish behaviour on invalid rounds to return "failure" string ("*0" or "*1"), instead of falling back to DES.
5.3.0 PHP now contains its own implementation for the MD5 crypt, Standard DES, Extended DES and the Blowfish algorithms and will use that if the system lacks of support for one or more of the algorithms.

Exemple

Example #1 crypt() examples

<?php
$hashed_password 
crypt('mypassword'); // let the salt be automatically generated

/* You should pass the entire results of crypt() as the salt for comparing a
   password, to avoid problems when different hashing algorithms are used. (As
   it says above, standard DES-based password hashing uses a 2-character salt,
   but MD5-based hashing uses 12.) */
if (hash_equals($hashed_passwordcrypt($user_input$hashed_password))) {
   echo 
"Password verified!";
}
?>

Example #2 Using crypt() with htpasswd

<?php
// Set the password
$password 'mypassword';

// Get the hash, letting the salt be automatically generated
$hash crypt($password);
?>

Example #3 Using crypt() with different hash types

<?php
/* These salts are examples only, and should not be used verbatim in your code.
   You should generate a distinct, correctly-formatted salt for each password.
*/
if (CRYPT_STD_DES == 1) {
    echo 
'Standard DES: ' crypt('rasmuslerdorf''rl') . "\n";
}

if (
CRYPT_EXT_DES == 1) {
    echo 
'Extended DES: ' crypt('rasmuslerdorf''_J9..rasm') . "\n";
}

if (
CRYPT_MD5 == 1) {
    echo 
'MD5:          ' crypt('rasmuslerdorf''$1$rasmusle$') . "\n";
}

if (
CRYPT_BLOWFISH == 1) {
    echo 
'Blowfish:     ' crypt('rasmuslerdorf''$2a$07$usesomesillystringforsalt$') . "\n";
}

if (
CRYPT_SHA256 == 1) {
    echo 
'SHA-256:      ' crypt('rasmuslerdorf''$5$rounds=5000$usesomesillystringforsalt$') . "\n";
}

if (
CRYPT_SHA512 == 1) {
    echo 
'SHA-512:      ' crypt('rasmuslerdorf''$6$rounds=5000$usesomesillystringforsalt$') . "\n";
}
?>

Exemplul de mai sus va afișa ceva similar cu:

Standard DES: rl.3StKT.4T8M
Extended DES: _J9..rasmBYk8r9AiWNc
MD5:          $1$rasmusle$rISCgZzpwk3UhDidwXvin0
Blowfish:     $2a$07$usesomesillystringfore2uDLvp1Ii2e./U9C8sBjqp8I90dH6hi
SHA-256:      $5$rounds=5000$usesomesillystri$KqJWpanXZHKq2BOB43TSaYhEWsQ1Lr5QNyPCDH/Tp.6
SHA-512:      $6$rounds=5000$usesomesillystri$D4IrlXatmP7rx3P3InaxBeoomnAihCKRVQP22JZ6EY47Wc6BkroIuUUBOov1i.S5KPgErtP/EN5mcO.ChWQW21

Note

Notă: There is no decrypt function, since crypt() uses a one-way algorithm.

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