Hello,
After several hours of research, I've come to the following discovery. Hopping it will help someone as much in distress as I was :
The VICredStore.pm module allows to use VIFP authentication and therefore avoid using hard-coded password for you Perl scripts.
If you want to use this module, you will have to point your script to the credential store which defaut location is in $HOME/.vmware/credstore/vicredentials.xml. However, if you registered your targets to VIFP using the vifp binary, the file created is in the same location (given that you use the vi-admin of vi-user accounts) but named vmacredentials.xml. Don't be fooled. Even though the two files have exactly the same structure, VICredStore.pm can't only desobfuscate password created through credstore_admin.pl add. Moreover this perl script will create the vicredentials.xml file in the home directory of the user, not the vi-admin and vi-user directories.
What's really misleading is that VICredStore::get_password() return the obfuscated password if you point it to the vmacredentials.xml file, not an error message.
Hopping you'll find this post if you are looking for a solution to this problem.
Regards,
Clement.