Pass Through Scenario adding extension

Hi Experts,

I have a simple pass through scenario where I am picking A.TXT, B.TXT and C.TXT using sender communication channel and encrypting then using .pgp keys. I want to

1. keep the names same

2. want to add the timestamp to it

3. want to add .pgp extension.

I am able to achieve 1 & 2 however not able to add the .pgp extension. Please advice how i can do it. Please note, i do not have mapping and the receiver is FTP(not SFTP, its possible in SFTP)

Thanks,

Nishant