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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY VERSION "1.0">
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<!ENTITY COMMANDNAME "password-request">
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<!ENTITY TIMESTAMP "2008-09-03">
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<!ENTITY COMMANDNAME "mandos-client">
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<!ENTITY TIMESTAMP "2009-01-24">
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<!ENTITY % common SYSTEM "../common.ent">
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<refentry xmlns:xi="http://www.w3.org/2001/XInclude">
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<title>Mandos Manual</title>
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<!-- Nwalsh’s docbook scripts use this to generate the footer: -->
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<!-- NWalsh’s docbook scripts use this to generate the footer: -->
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<productname>Mandos</productname>
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<productnumber>&VERSION;</productnumber>
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<productnumber>&version;</productnumber>
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<date>&TIMESTAMP;</date>
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<refname><command>&COMMANDNAME;</command></refname>
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Client for <application>Mandos</application>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--connect
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<replaceable>IPADDR</replaceable><literal>:</literal
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<replaceable>ADDRESS</replaceable><literal>:</literal
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><replaceable>PORT</replaceable></option></arg>
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<arg choice="plain"><option>-c
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<replaceable>IPADDR</replaceable><literal>:</literal
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<replaceable>ADDRESS</replaceable><literal>:</literal
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><replaceable>PORT</replaceable></option></arg>
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<arg choice="plain"><option>--keydir
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg choice="plain"><option>-d
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg choice="plain"><option>--interface
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<replaceable>NAME</replaceable></option></arg>
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<arg choice="plain"><option>-i
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</refsynopsisdiv>
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<refsect1 id="description">
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<title>DESCRIPTION</title>
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<command>&COMMANDNAME;</command> is a client program that
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communicates with <citerefentry><refentrytitle
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>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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to get a password. It uses IPv6 link-local addresses to get
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network connectivity, Zeroconf to find the server, and TLS with
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an OpenPGP key to ensure authenticity and confidentiality. It
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keeps running, trying all servers on the network, until it
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receives a satisfactory reply.
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to get a password. In slightly more detail, this client program
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brings up a network interface, uses the interface’s IPv6
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link-local address to get network connectivity, uses Zeroconf to
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find servers on the local network, and communicates with servers
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using TLS with an OpenPGP key to ensure authenticity and
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confidentiality. This client program keeps running, trying all
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servers on the network, until it receives a satisfactory reply
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or a TERM signal is received. If no servers are found, or after
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all servers have been tried, it waits indefinitely for new
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This program is not meant to be run directly; it is really meant
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This program could, theoretically, be used as a keyscript in
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<filename>/etc/crypttab</filename>, but it would then be
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impossible to enter the encrypted root disk password at the
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console, since this program does not read from the console at
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all. This is why a separate plugin does that, which will be run
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in parallell to this one.
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impossible to enter a password for the encrypted root disk at
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the console, since this program does not read from the console
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at all. This is why a separate plugin runner (<citerefentry>
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<refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
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both this program and others in in parallel,
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<emphasis>one</emphasis> of which will prompt for passwords on
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<refsect1 id="files">
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<title>FILES</title>
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<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
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<term><filename>/conf/conf.d/mandos/seckey.txt</filename
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OpenPGP public and private key files, in <quote>ASCII
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Armor</quote> format. These are the default file names,
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they can be changed with the <option>--pubkey</option> and
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<option>--seckey</option> options.
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<!-- <refsect1 id="bugs"> -->
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<!-- <title>BUGS</title> -->
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<refsect1 id="example">
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<title>EXAMPLE</title>
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Note that normally, command line options will not be given
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directly, but via options for the Mandos <citerefentry
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><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>.
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Normal invocation needs no options, if the network interface
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is <quote>eth0</quote>:
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<userinput>&COMMANDNAME;</userinput>
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Search for Mandos servers (and connect to them) using another
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<userinput>&COMMANDNAME; --interface eth1</userinput>
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Run in debug mode, and use a custom key:
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
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Run in debug mode, with a custom key, and do not use Zeroconf
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to locate a server; connect directly to the IPv6 address
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<quote><systemitem class="ipaddress"
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>2001:db8:f983:bd0b:30de:ae4a:71f2:f672</systemitem></quote>,
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port 4711, using interface eth2:
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect 2001:db8:f983:bd0b:30de:ae4a:71f2:f672:4711 --interface eth2</userinput>
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<refsect1 id="security">
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<title>SECURITY</title>
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This program is set-uid to root, but will switch back to the
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original (and presumably non-privileged) user and group after
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bringing up the network interface.
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To use this program for its intended purpose (see <xref
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linkend="purpose"/>), the password for the root file system will
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have to be given out to be stored in a server computer, after
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having been encrypted using an OpenPGP key. This encrypted data
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which will be stored in a server can only be decrypted by the
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OpenPGP key, and the data will only be given out to those
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clients who can prove they actually have that key. This key,
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however, is stored unencrypted on the client side in its initial
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<acronym>RAM</acronym> disk image file system. This is normally
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readable by all, but this is normally fixed during installation
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of this program; file permissions are set so that no-one is able
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The only remaining weak point is that someone with physical
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access to the client hard drive might turn off the client
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computer, read the OpenPGP keys directly from the hard drive,
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and communicate with the server. To safeguard against this, the
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server is supposed to notice the client disappearing and stop
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giving out the encrypted data. Therefore, it is important to
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set the timeout and checker interval values tightly on the
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server. See <citerefentry><refentrytitle
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>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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It will also help if the checker program on the server is
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configured to request something from the client which can not be
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spoofed by someone else on the network, unlike unencrypted
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<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
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<emphasis>Note</emphasis>: This makes it completely insecure to
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have <application >Mandos</application> clients which dual-boot
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to another operating system which is <emphasis>not</emphasis>
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trusted to keep the initial <acronym>RAM</acronym> disk image
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<refsect1 id="see_also">
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<title>SEE ALSO</title>
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<citerefentry><refentrytitle>cryptsetup</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>crypttab</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>mandos</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>password-prompt</refentrytitle>
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<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>
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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
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<ulink url="http://www.avahi.org/">Avahi</ulink>
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url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
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url="http://www.gnupg.org/related_software/gpgme/"
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<citation>RFC 4880: <citetitle>OpenPGP Message
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Format</citetitle></citation>
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<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
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Transport Layer Security</citetitle></citation>
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<citation>RFC 4291: <citetitle>IP Version 6 Addressing
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Architecture</citetitle>, section 2.5.6, Link-Local IPv6
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Unicast Addresses</citation>
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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
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Zeroconf is the network protocol standard used for finding
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Mandos servers on the local network.
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<ulink url="http://www.avahi.org/">Avahi</ulink>
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Avahi is the library this program calls to find Zeroconf
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<ulink url="http://www.gnu.org/software/gnutls/"
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GnuTLS is the library this client uses to implement TLS for
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communicating securely with the server, and at the same time
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send the public OpenPGP key to the server.
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<ulink url="http://www.gnupg.org/related_software/gpgme/"
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GPGME is the library used to decrypt the OpenPGP data sent
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RFC 4291: <citetitle>IP Version 6 Addressing
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Architecture</citetitle>
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<term>Section 2.2: <citetitle>Text Representation of
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Addresses</citetitle></term>
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<listitem><para/></listitem>
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<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
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Address</citetitle></term>
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<listitem><para/></listitem>
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<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
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Addresses</citetitle></term>
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This client uses IPv6 link-local addresses, which are
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immediately usable since a link-local addresses is
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automatically assigned to a network interfaces when it
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RFC 4346: <citetitle>The Transport Layer Security (TLS)
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Protocol Version 1.1</citetitle>
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TLS 1.1 is the protocol implemented by GnuTLS.
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RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
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The data received from the server is binary encrypted
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RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
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This is implemented by GnuTLS and used by this program so
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that OpenPGP keys can be used.
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