sodium_crypto_pwhash_str

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_pwhash_str — Get an ASCII-encoded hash

Description

sodium_crypto_pwhash_str(#[\SensitiveParameter] string $password, int $opslimit, int $memlimit): string

Uses a CPU- and memory-hard hash algorithm along with a randomly-generated salt, and memory and CPU limits to generate an ASCII-encoded hash suitable for password storage.

Parameters

password: string; The password to generate a hash for.
opslimit: Represents a maximum amount of computations to perform. Raising this number will make the function require more CPU cycles to compute a key. There are constants available to set the operations limit to appropriate values depending on intended use, in order of strength: SODIUM_CRYPTO_PWHASH_OPSLIMIT_INTERACTIVE, SODIUM_CRYPTO_PWHASH_OPSLIMIT_MODERATE and SODIUM_CRYPTO_PWHASH_OPSLIMIT_SENSITIVE.
memlimit: The maximum amount of RAM that the function will use, in bytes. There are constants to help you choose an appropriate value, in order of size: SODIUM_CRYPTO_PWHASH_MEMLIMIT_INTERACTIVE, SODIUM_CRYPTO_PWHASH_MEMLIMIT_MODERATE, and SODIUM_CRYPTO_PWHASH_MEMLIMIT_SENSITIVE. Typically these should be paired with the matching opslimit values.

Return Values

Returns the hashed password.

In order to produce the same password hash from the same password, the same values for opslimit and memlimit must be used. These are embedded within the generated hash, so everything that's needed to verify the hash is included. This allows the sodium_crypto_pwhash_str_verify() function to verify the hash without needing separate storage for the other parameters.

Examples

Example #1 sodium_crypto_pwhash_str() example

<?php
$password = 'password';
echo sodium_crypto_pwhash_str(
    $password,
    SODIUM_CRYPTO_PWHASH_OPSLIMIT_INTERACTIVE,
    SODIUM_CRYPTO_PWHASH_MEMLIMIT_INTERACTIVE
);

The above example will output something similar to:

$argon2id$v=19$m=65536,t=2,p=1$oWIfdaXwWwhVmovOBc2NAQ$EbsZ+JnZyyavkafS0hoc4HdaOB0ILWZESAZ7kVGa+Iw

Notes

Note:
Hashes are calculated using the Argon2ID algorithm, providing resistance to both GPU and side-channel attacks. In contrast to the password_hash() function, there is no salt parameter (a salt is generated automatically), and the opslimit and memlimit parameters are not optional.

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User Contributed Notes 1 note

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marcus at synchromedia dot co dot uk ¶

3 years ago

If you want to ensure that the hashes you generate with sodium_crypto_pwhash_str are compatible with those generated by password_hash, you need to keep an eye on that memory setting. According to the docs, the password_hash memory_cost param is given in "kibibytes", whereas sodium_crypto_pwhash_str uses bytes. I did some experiments to see what the difference is and ran into this:

echo password_hash('password',
                   PASSWORD_ARGON2ID,
                   [
                       'memory_cost' => 15000,
                       'time_cost'   => 26,
                       'threads'     => 1,
                   ];

echo sodium_crypto_pwhash_str(
        'password', 26,
        15000000);

These result in:
$argon2id$v=19$m=15000,t=26,p=1$VG5MSkhUdEdFaGwyVG5sWA$laRHogIVAnC4ggLI8RdCDWlITTdicrdq0tK6SHGf4CI
$argon2id$v=19$m=14648,t=26,p=1$ClQ37/z9u7K6V1C2bkD4QA$51m8KhQQ9gujFSF+JyQR9d5QesayJiKsFmDU4HnGBHg

Notice that the "m=" numbers are different, and also different from what we asked for. It's down to the "kibibytes" unit. If we multiply the 15000 we used for password_hash by 1,024 instead of 1,000, we get 15,360,000, and using that number gives us the expected hash params:

echo sodium_crypto_pwhash_str(
        'password', 26,
        15360000);

$argon2id$v=19$m=15000,t=26,p=1$Qz3pWktOvT6X/LvdAk0bgQ$KosSFPfHUtWg+ppyRs3Op5/zIV6F6iy2Q7Gom8wP29c

This should be compatible with password_hash.

Incidentally the numbers I'm using for the Argon2id hash params are taken from the OWASP password guide, which recommend values different from PHP's default: https://cheatsheetseries.owasp.org/cheatsheets/Password_Storage_Cheat_Sheet.html#argon2id