Installing SSL Certs to Use with gFTP

[Peter Axup]

Dear MacPorts-Users,

I'm a new MacPorts user.  For my first installation, I installed gFTP  
because I wanted to use FTP with an IBackup.com account.

I have an iBook G4 running Mac OS X 10.4.8 (PPC), MacPorts 1.320, X11  
1.1.1 and Xcode 2.4.

I successfully installed MacPorts and gFTP.  I successfully used gFTP  
in the unencrypted FTP mode and both uploaded and downloaded a file  
from IBackup.com.

I also successfully uploaded and downloaded a file using a trial copy  
of Panic Transmit 3 using FTP with SSL, so I'm pretty sure I got the  
IBackup.com settings right.

I would like to use gFTP in the SSL mode.  When I tried it, I got an  
error message.  Here is the activity log:
Looking up secure3.ibackup.com
Trying secure3.ibackup.com:27
Connected to secure3.ibackup.com:27
220-FTP with SSL Encryption Enabled
220 IBackup FTP Server Ready.
AUTH TLS
234 AUTH Command OK. Initializing SSL connection.
Error with certificate at depth: 0
Issuer = /C=GB/O=Comodo Limited/OU=Comodo Trust Network/OU=Terms and  
Conditions of use: http://www.comodo.net/repository/OU=(c)2002 Comodo  
Limited/CN=Comodo Class 3 Security Services CA
Subject = /C=US/postalCode=91367/ST=California/L=Woodland Hills/ 
streetAddress=Suite 270/streetAddress=21300 Victory Blvd/O=Pro  
Softnet Corp/OU=IBackup Division/OU=Issued through Pro Softnet Corp.  
E-PKI Manager/OU=InstantSSL/CN=secure.ibackup.com
Error 20:unable to get local issuer certificate
Disconnecting from site secure3.ibackup.com

So, I have a certificate problem.  I looked through the MacPorts  
GMANE archive and couldn't find anything related to gFTP.  This may  
be more of an SSL question, but I don't have a clue where to start.
a.  Do I need to install another application using MacPorts, such as  
openssl?
b.  How do I get and install certificates?

Thank you.
Peter