decrypt.rb

[Dave]

Per the Dovecot site here:
https://wiki.dovecot.org/Plugins/MailCrypt
... the "decrypt.rb" ruby script can be used to decrypt a 
Dovecot-encrypted message file from the command line.  The script sort 
of runs successfully for me, in the sense that it doesn't error out, but 
it doesn't show the decrypted message.

I've called it like so:
decrypt.rb -k <PATH_TO_DOVECOT_KEYFILE> -f ./encrypted_message

But when I do it just displays the info below and exits (I've subbed 
<DATA> tags for the actual data):

------------------[OUTPUT]-----------------------

Key(s) (total: 1)
   - Key type  : EC
   - Key digest: <DATA1>
   - Peer key  : <DATA2>
   - Encrypted : <DATA3>
   - Kd hash   : <DATA4>

-------------------------------------------------------

I've tried specifying an output file as well, per the script's command 
line options, but the output file is 0 bytes.  Does anyone have any 
suggestions?  I *think* I'm using it the way it's intended to be used, 
but maybe I'm not?!

-Dave