Description
string crypt(string str, string [
salt]);
crypt() will encrypt a string using the
standard Unix DES encryption method. Arguments
are a string to be encrypted and an optional two-character salt
string to base the encryption on. See the Unix man page for your
crypt function for more information.
If the salt argument is not provided, it will be randomly generated
by PHP.
Some operating systems support more than one type of encryption.
In fact, sometimes the standard DES encryption is replaced by an
MD5 based encryption algorithm. The encryption type is triggered by
the salt argument. At install time, PHP determines the capabilities
of the crypt function and will accept salts for other encryption
types. If no salt is provided, PHP will auto-generate a standard
2-character DES salt by default unless the default encryption type
on the system is MD5 in which case a random MD5-compatible salt
is generated. PHP sets a constant named CRYPT_SALT_LENGTH which
tells you whether a regular 2-character salt applies to your system
or the longer 12-char MD5 salt is applicable.
The standard DES encryption crypt() contains
the salt as the first two characters of the output.
On systems where the crypt() function supports multiple encryption
types, the following constants are set to 0 or 1 depending on whether
the given type is available:
CRYPT_STD_DES - Standard DES encryption with a 2-char SALT
CRYPT_EXT_DES - Extended DES encryption with a 9-char SALT
CRYPT_MD5 - MD5 encryption with a 12-char SALT starting with $1$
CRYPT_BLOWFISH - Extended DES encryption with a 16-char SALT starting with $2$
There is no decrypt function, since crypt()
uses a one-way algorithm.
Manual: crypt
