The right Perl cryptomodules need to be installed.
Do an apt-get install libcrypt-des-perl
to get the right module.
Additionally, apt-get install libdigest-hmac-perl
will install the Digest/HMAC module. If this is skipped then following error will be displayed:
# Dropping host '10.0.0.2': SNMPv3 support is unavailable (Required module Digest/HMAC.pm not found)