Decrypting 2 files which were merged into 1

[ravi shankar]

Hi All,

We have been using gnupg to decrypt files pulled from a customer FTP
server. On the customer side, the software used is some financial
gateway software which sets flags for each of the files.
Based on those flags we are given permission to pull those and
decrypt. Sometimes there are 2 encrypted files placed on the customer
side with the same name, not sure how thats possible on that financial
gateway.So we have 2 encrypted files at their end with same name, say
suppose one of 2 MB and the other 3 MB, when we fetch those at one go
using FTP we are getting a combined encrypted file of 5 MB.

This 5 MB file is then decrypted using our gnupg key to get the data
out of it. Now when we decrypt, we are only seeing one set of data and
other 3 MB data of the second file is lost.
We are using the following command to decrypt
echo "password" | gpg --verbose --no-tty --no-secmem-warning
--passphrase-fd 0 "$fpgp"

And we get the following trace

> gpg: armor header: Version: GnuPG v1.2.1 (AIX) stderr
> gpg: Signature made Wed Apr 2 16:32:08 2008 EDT using DSA key ID F83564E3 stderr
> gpg: Can't check signature: public key not found stderr
> gpg: onepass_sig with unknown version 73 stderr
> gpg: WARNING: encrypted message has been manipulated!
stderr> gpg: [don't know]: invalid packet (ctb=42)

Though we get data of 1 file out of it correctly.

Is there a way to decrypt the merged file correctly and extract entire
data of both encrypted files within it correctly using gnupg?

Thanks,
Ravi