wget http://www.tcpdump.org/tcpdump-workers.asc
gpg --import tcpdump-workers.asc
gpg: directory `/home/bozo/.gnupg' created
gpg: new configuration file `/home/bozo/.gnupg/gpg.conf' created
gpg: WARNING: options in `/home/bozo/.gnupg/gpg.conf' are not yet active during this run
gpg: keyring `/home/bozo/.gnupg/secring.gpg' created
gpg: keyring `/home/bozo/.gnupg/pubring.gpg' created
gpg: /home/bozo/.gnupg/trustdb.gpg: trustdb created
gpg: key 89E917F3: public key "tcpdump.org (SIGNING KEY) <tcpdump-workers@tcpdump.org>" imported
gpg: Total number processed: 1
gpg: imported: 1
gpg: no ultimately trusted keys found
wget http://www.tcpdump.org/release/libpcap-0.9.7.tar.gz
wget http://www.tcpdump.org/release/libpcap-0.9.7.tar.gz.sig
gpg --verify libpcap-0.9.7.tar.gz.sig
gpg: Signature made Tue Jul 24 09:46:13 2007 ICT using RSA key ID E99DD5FD
gpg: Can't check signature: public key not found
Either sign with the key in tcpdump-workers.asc or update that file. I cannot upgrade libpcap because it appears to be hacked (or at least your web site was) since the gpg signatures for libpcap (and tcpdump) cannot be verified
Administrators of the "libpcap" SourceForge project have superseded this tracker item (formerly artifact 1773453, now bug 95) with issue 97 of the "libpcap" GitHub project.