<dd>The restriction of access to network realms. In an Apache context
usually the restriction of access to certain <em>URLs</em>.<br />
See: <a href="howto/auth.html">Authentication, Authorization, and Access
Control</a></dd>
<dt><a name="algorithm">Algorithm</a></dt>
<dd>An unambiguous formula or set of rules for solving a problem in
a finite number of steps. Algorithms for encryption are usually called
<dfn>Ciphers</dfn>.</dd>
<dt><a name="apacheextensiontool">APache eXtension Tool</a> <a name="apxs">(apxs)</a></dt> <dd>A perl script that aids in compiling <a href="#module">module</a> sources into Dynamic Shared Objects (<a href="#dso">DSO</a>s) and helps install them in the Apache Web
<a name="csr">(CSR)</a></dt> <dd>An unsigned <a href="#certificate">certificate</a> for submission to a <a href="#certificationauthority">Certification Authority</a>, which signs it
with the <a href="#privatekey">Private Key</a> of their CA
<em>Certificate</em>. Once the CSR is signed, it becomes a real
certificate.<br />
See: <a href="ssl/">SSL/TLS Encryption</a></dd>
<dt><a name="cipher">Cipher</a></dt> <dd>An algorithm or system for
data encryption. Examples are DES, IDEA, RC4, etc.<br />
See: <a href="ssl/">SSL/TLS Encryption</a></dd>
<dt><a name="ciphertext">Ciphertext</a></dt> <dd>The result after <a href="#plaintext">Plaintext</a> is passed through a <a href="#cipher">Cipher</a>.<br /> See: <a href="ssl/">SSL/TLS
Encryption</a></dd>
<dt><a name="commongatewayinterface">Common Gateway Interface</a> <a name="cgi">(CGI)</a></dt> <dd>A standard definition for an interface
between a web server and an external program that allows the external
program to service requests. The interface was originally defined by
<a href="http://hoohoo.ncsa.uiuc.edu/cgi/overview.html">NCSA</a> but
there is also an <a href="http://cgi-spec.golux.com/">RFC
project</a>.<br />
See: <a href="howto/cgi.html">Dynamic Content with CGI</a></dd>
<dd>A hash of a message, which can be used to verify that the contents of
the message have not been altered in transit.<br />
See: <a href="ssl/">SSL/TLS Encryption</a></dd>
<dt><a name="mime-type">MIME-type</a></dt> <dd>A way to describe the
kind of document being transmitted. Its name comes from that fact
that its format is borrowed from the Multipurpose Internet Mail
Extensions. It consists of a major type and a minor type, separated
by a slash. Some examples are <code>text/html</code>,
<code>image/gif</code>, and <code>application/octet-stream</code>. In
HTTP, the MIME-type is transmitted in the <code>Content-Type</code> <a href="#header">header</a>.<br /> See: <a href="mod/mod_mime.html">mod_mime</a></dd>
<dt><a name="module">Module</a></dt> <dd>An independent part of a
program. Much of Apache's functionality is contained in modules that
you can choose to include or exclude. Modules that are compiled into
the Apache httpd binary are called <em>static modules</em>, while
modules that are stored separately and can be optionally loaded at
run-time are called <em>dynamic modules</em> or <a href="#dso">DSOs</a>. Modules that are included by default are called
<em>base modules</em>. Many modules are available for Apache that are
not distributed as part of the Apache HTTP Server <a href="#tarball">tarball</a>. These are referred to as <em>third-party