Secure apt feature has been added to 0.5 and experimental repositories.  
Although apt-get complains about the key is missing, you could still be able to 
add the packages from voyage apt repository with the key.

To add the public key to apt key rings and get rid of the error messages:

# wget http://www.voyage.hk/dists/experimental/archive.key -O - | apt-key add -

Icon  Name                    Last modified      Size  Description
[DIR] Parent Directory - [   ] Packages 18-May-2012 15:00 81K [   ] Packages.gz 18-May-2012 15:00 19K [TXT] Readme.txt 03-Jun-2008 09:27 370 [   ] Release 18-May-2012 15:00 1.1K [   ] Release.gpg 18-May-2012 15:00 197 [   ] Sources 18-May-2012 15:00 21K [   ] Sources.gz 18-May-2012 15:00 6.7K [DIR] aircrack-ng/ 08-Feb-2011 14:28 - [DIR] alsa-driver/ 30-Jun-2011 01:34 - [DIR] alsa-lib/ 12-Oct-2011 17:03 - [DIR] alsa-tools/ 12-Oct-2011 17:03 - [DIR] alsa-utils/ 12-Oct-2011 17:03 - [DIR] alsa/ 13-May-2012 23:30 - [   ] archive.key 18-May-2012 15:00 1.7K [DIR] asterisk-addons/ 15-Oct-2010 18:18 - [DIR] asterisk-core-sounds/ 25-Oct-2011 11:38 - [DIR] asterisk-extra-sounds/ 30-Jun-2011 01:34 - [DIR] asterisk-gui/ 25-Oct-2011 11:38 - [DIR] asterisk-moh-opsound/ 15-Oct-2010 18:30 - [DIR] asterisk/ 15-May-2012 00:01 - [DIR] atl1e/ 08-Jul-2009 01:44 - [DIR] atl2/ 08-Jul-2009 01:44 - [DIR] aufs/ 12-Sep-2011 17:11 - [DIR] awds/ 27-May-2010 13:16 - [DIR] batctl/ 30-Jun-2011 01:34 - [DIR] batman/ 13-May-2012 23:30 - [DIR] batmand/ 13-May-2012 23:31 - [DIR] bcm43xx-fwcutter/ 01-Jun-2006 22:24 - [TXT] build.sh 31-May-2008 12:02 576 [DIR] busybox/ 15-Nov-2006 23:07 - [DIR] casper/ 07-Oct-2006 00:42 - [DIR] crda/ 30-Jun-2011 01:34 - [DIR] dahdi-firmware/ 15-May-2012 00:01 - [DIR] dahdi-linux/ 15-May-2012 00:02 - [DIR] dahdi-tools/ 15-May-2012 00:02 - [DIR] dahdi/ 15-May-2012 00:03 - [DIR] et131x/ 08-Jul-2009 01:44 - [DIR] frottle/ 01-Jun-2006 22:24 - [DIR] fxload/ 15-Oct-2010 18:23 - [DIR] glib1.2/ 30-Jun-2011 01:34 - [DIR] haserl/ 15-Nov-2006 23:07 - [DIR] hostapd/ 25-Oct-2011 11:38 - [DIR] ieee80211/ 01-Jun-2006 22:39 - [DIR] ieee80211softmac/ 01-Jun-2006 22:39 - [DIR] ipw2100/ 01-Jun-2006 22:39 - [DIR] ipw2200/ 01-Jun-2006 22:39 - [DIR] iw/ 25-Oct-2011 11:38 - [DIR] lame/ 07-Apr-2012 15:13 - [DIR] lcr/ 08-Feb-2011 14:28 - [DIR] libav/ 22-Apr-2012 22:03 - [DIR] libcue/ 22-Feb-2010 12:13 - [DIR] libffado/ 25-Oct-2011 11:38 - [DIR] libgea2/ 23-Jun-2008 01:44 - [DIR] libgea3/ 27-May-2010 13:16 - [DIR] libnl3/ 25-Oct-2011 11:38 - [DIR] libpri/ 13-Feb-2012 19:07 - [DIR] libresample/ 15-Oct-2010 18:26 - [DIR] libss7/ 15-Oct-2010 18:17 - [DIR] linux/ 15-May-2012 00:00 - [DIR] lirc/ 12-Sep-2011 17:11 - [DIR] lzma/ 08-Jul-2009 01:44 - [DIR] madwifi-ifupdown/ 28-Jan-2007 23:43 - [DIR] madwifi-ng/ 15-Nov-2006 23:07 - [DIR] madwifi-tools/ 08-Feb-2011 14:28 - [DIR] madwifi/ 12-Sep-2011 17:11 - [TXT] maintainers.sh 17-Mar-2005 10:23 108 [DIR] minidlna/ 17-Feb-2012 00:52 - [DIR] misdn-kernel/ 08-Feb-2011 14:28 - [DIR] misdn-user/ 08-Feb-2011 14:28 - [DIR] misdn/ 11-Oct-2011 01:44 - [DIR] misdnv2user/ 08-Feb-2011 14:28 - [DIR] mpd/ 15-May-2012 00:00 - [DIR] ncurses/ 12-Oct-2011 17:02 - [DIR] ndiswrapper/ 12-Sep-2011 17:11 - [DIR] nginx/ 01-Apr-2012 16:14 - [DIR] nocatauth/ 01-Jun-2006 22:24 - [DIR] nocatsplash/ 30-Jun-2011 01:34 - [DIR] olsrd/ 27-May-2010 13:16 - [DIR] openr2/ 13-Feb-2012 19:07 - [DIR] openssl/ 22-Feb-2010 12:13 - [DIR] openswan/ 13-Jul-2008 12:11 - [DIR] p910nd/ 23-Jul-2007 14:23 - [DIR] parprouted/ 01-Jun-2006 22:24 - [TXT] promote.sh 08-Jan-2009 13:05 241 [DIR] rt2400/ 01-Jun-2006 22:39 - [DIR] rt2500/ 01-Jun-2006 22:39 - [DIR] rt2860/ 08-Jul-2009 01:44 - [DIR] spandsp/ 15-May-2012 00:02 - [DIR] squashfs-tools/ 22-Feb-2010 12:13 - [DIR] squashfs/ 22-Feb-2010 12:13 - [DIR] sysvinit/ 11-Oct-2011 14:59 - [DIR] voyage-util/ 23-Nov-2011 16:42 - [DIR] wavemon/ 27-May-2010 13:16 - [DIR] wifidog/ 01-Jun-2006 22:24 - [DIR] wireless-regdb/ 30-Jun-2011 01:34 - [DIR] wireless-tools/ 13-Jul-2008 12:11 - [DIR] wpasupplicant/ 25-Oct-2011 11:38 - [DIR] x264/ 20-Apr-2012 14:32 - [DIR] xvidcore/ 20-Apr-2012 14:33 - [DIR] zaptel/ 08-Jul-2009 01:44 -
Apache/2.2.9 (Debian) DAV/2 SVN/1.5.1 PHP/5.2.6-1+lenny16 with Suhosin-Patch Server at www.voyage.hk Port 80