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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.6 $ -->
<refentry xml:id="function.mhash-keygen-s2k" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>mhash_keygen_s2k</refname>
<refpurpose>Generates a key</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>string</type><methodname>mhash_keygen_s2k</methodname>
<methodparam><type>int</type><parameter>hash</parameter></methodparam>
<methodparam><type>string</type><parameter>password</parameter></methodparam>
<methodparam><type>string</type><parameter>salt</parameter></methodparam>
<methodparam><type>int</type><parameter>bytes</parameter></methodparam>
</methodsynopsis>
<para>
Generates a key according to the <parameter>hash</parameter> given a user
provided <parameter>password</parameter>.
</para>
<para>
This is the Salted S2K algorithm as specified in the OpenPGP
document (<link xlink:href="&url.rfc;2440">RFC 2440</link>).
</para>
<para>
Keep in mind that user supplied passwords are not really suitable
to be used as keys in cryptographic algorithms, since users normally
choose keys they can write on keyboard. These passwords use
only 6 to 7 bits per character (or less). It is highly recommended
to use some kind of transformation (like this function) to the user
supplied key.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>hash</parameter></term>
<listitem>
<para>
The hash id used to create the key.
One of the <literal>MHASH_XXX</literal> constants.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>password</parameter></term>
<listitem>
<para>
User supplied password.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>salt</parameter></term>
<listitem>
<para>
Must be different and random enough for every key you generate in
order to create different keys. That salt must be known when you check
the keys, thus it is a good idea to append the key to it. Salt has a
fixed length of 8 bytes and will be padded with zeros if you supply
less bytes.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>bytes</parameter></term>
<listitem>
<para>
The key length, in bytes.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns the generated key as a string, or &false; on error.
</para>
</refsect1>
</refentry>
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