bcrypt($password, $subtype, $cost, $salt)

This computes the bcrypt hash for $password in $subtype, with $cost and $salt.

Valid subtypes are:

• "2b"

  This is the subtype the rest of the world has been using since 2014, you should use this unless you have a very specific reason to use something else.

• "2a"

  This is an old and subtly buggy version of bcrypt. This is mainly useful for Crypt::Eksblowfish compatibility.

• "2y"

  This type is considered equivalent to "2b", and is only commonly used on php.

• "2x"

  This is a very broken version that is only useful for compatibility with ancient php versions.

$cost must be between 4 and 31 (inclusive). $salt must be exactly 16 bytes.

bcrypt_check($password, $hash)

This checks if the $password satisfies the $hash, and does so in a timing-safe manner.

bcrypt_prehashed($password, $subtype, $cost, $salt, $hash_algorithm)

This works like the "bcrypt" functions, but pre-hashes the password using the specified hash. This is mainly useful to get around the 72 character limit. Currently 'sha256', 'sha384' and 'sha512' are supported (but note that sha512 doesn't actually fit in bcrypt's input limit so is a bit moot), this is keyed with the salt to prevent password shucking. If $hash_algorithm is an empty string it will perform a normal "bcrypt" operation.

bcrypt_check_prehashed($password, $hash)

This verifies pre-hashed passwords as generated by "bcrypt_prehashed".

bcrypt_needs_rehash($hash, $wanted_subtype, $wanted_cost, $wanted_hash = '')

This returns true if the bcrypt hash uses a different subtype, cost or hash algorithm than desired.

bcrypt_supported_prehashes()

This returns a list of supported prehashes. Current that's "('sha256', 'sha384', 'sha512')" but in the future it may include more.