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<HTML
><HEAD
><TITLE
>crypt</TITLE
><META
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><H1
><A
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>crypt</A
></H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN36372"
></A
><P
> (PHP3 , PHP4 )</P
>crypt -- DES-encrypt a string</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN36375"
></A
><H2
>Description</H2
><DIV
CLASS="funcsynopsis"
><A
NAME="AEN36377"
></A
><P
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>string <B
CLASS="function"
>crypt</B
></CODE
> (string str [, string
salt])</CODE
></P
><P
></P
></DIV
><P
> <B
CLASS="function"
>crypt()</B
> will encrypt a string using the
standard Unix <SPAN
CLASS="abbrev"
>DES</SPAN
> 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.
</P
><P
> If the salt argument is not provided, one will be randomly
generated by PHP.
</P
><P
> 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.
</P
><P
> If you are using the supplied salt, you should be aware that the
salt is generated once. If you are calling this function
recursively, this may impact both appearance and, to a certain
extent, security.
</P
><P
> The standard DES encryption <B
CLASS="function"
>crypt()</B
> contains
the salt as the first two characters of the output.
</P
><P
> 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:
</P
><P
></P
><UL
><LI
><P
> CRYPT_STD_DES - Standard DES encryption with a 2-char SALT
</P
></LI
><LI
><P
> CRYPT_EXT_DES - Extended DES encryption with a 9-char SALT
</P
></LI
><LI
><P
> CRYPT_MD5 - MD5 encryption with a 12-char SALT starting with
$1$
</P
></LI
><LI
><P
> CRYPT_BLOWFISH - Extended DES encryption with a 16-char SALT
starting with $2$
</P
></LI
></UL
><P
> There is no decrypt function, since <B
CLASS="function"
>crypt()</B
>
uses a one-way algorithm.
</P
><P
> See also: <A
HREF="function.md5.html"
><B
CLASS="function"
>md5()</B
></A
>.
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