How to write a script for the below mentioned issue

hello Forum members,

I have a encrypted file which consist Unames and Pwd in the encrypted form and i have to write a script the PWD from the file and redirect into a log file.please find below the file and please help write a script.
_config.id_dbs is the file which will open with a customized command ie
mkidcfg.while we run with this command it displays 4 options
1 - Search for an ID
2 - Add an ID
3 - Update an ID
0 - Exit.
now i have to extract pwd from the above file and redirect into log file .
for example.
if we do cat _config.id_dbs
tag_id uname pwd
t_bca_db:Q@JbZF@:yGn8EaX
q_ertu_c:62:yC
a_xcvb_f:1NrsYUC:fEDEWv@bY9
please let me know for best script for the file .Its Urgent.iam looking forward from you.

Thanks & Reagrads
Rajkumar g:)