encryption bloats file

[Scott Lambdin]

The vender told our trading partner their PGP software bloats the file and
that is just the way it is.  I do not understand how the encrypted file (or
the file that contains the encrypted file) can be over twice the size of the
original, when the senders believe they have used compression.

I also wonder why gpg doesn't report whatever extra junk exists in the file.

--Scott

$ gpg --list-packets archive/somefile.061610.081519.pgp
gpg: WARNING: using insecure memory!
gpg: please see http://www.gnupg.org/faq.html for more information
:pubkey enc packet: version 3, algo 1, keyid BOOBFACEB00BFACE
        data: [2048 bits]
You need a passphrase to unlock the secret key for
user: "Bob Lawblaw <nacho4 at woof.gov>"
2048-bit RSA key, ID B00BFACE, created 1846-17-15
:encrypted data packet:
        length: 50160977
gpg: encrypted with 2048-bit RSA key, ID B00BFACE, created 1846-17-15
      "Bob Lawblaw <nacho4 at woof.gov>"
:compressed packet: algo=1
:literal data packet:
        mode t (74), created 1509949440, name="BLAH.BLAHBLAH.BLA.BLAHBL",
        raw data: 271163905 bytes
gpg: WARNING: message was not integrity protected
$



On Fri, Jan 9, 2009 at 11:49 PM, David Shaw <dshaw at jabberwocky.com> wrote:

>  On Fri, Jan 09, 2009 at 10:33:52PM -0500, Scott Lambdin wrote:
> > I found a file in rejects, but it may be partial.  It gives us some
> > information, though.
> >
> > The pgp file was 406184088 bytes and unencrypted is 175246253 bytes.
> >
> > gpg -v -v -o a_file.out -d a_file.pgp
> >
> > gpg: armor: BEGIN PGP MESSAGE
> > gpg: armor header: Version: McAfee E-Business Server v7.5 - Full License
> > :pubkey enc packet: version 3, algo 1, keyid 123456789012345
> >         data: [2047 bits]
> > gpg: public key is ABCD1234
> > You need a passphrase to unlock the secret key for
> > user: "Janeane Garofalo <JG at thyservice.com>"
> > 2048-bit RSA key, ID ABCD4321
> >
> > gpg: public key encrypted data: good DEK
> > :encrypted data packet:
> >         length: 42097820
> > gpg: encrypted with 2048-bit RSA key, ID ABCD4321
> > gpg: IDEA encrypted data
> > :compressed packet: algo=1
> > :literal data packet:
> >         mode t (74), created 1509949440, name="file-100-1",
> >         raw data: 227869810 bytes
> > gpg: original file name="file100"
> > gpg: no valid OpenPGP data found.
> > gpg: fatal: zlib inflate problem: invalid block type
> > secmem usage: 2208/4704 bytes in 5/15 blocks of pool 4960/32768
>
> That's helpful, as it indicates that the file was corrupt.  This could
> explain why an encrypted file is so much larger than the decrypted
> file - the decrypted file is truncated because the decryption failed
> partway through.  Of course, that could just be this rejected file.
>
> Can you check if your real file has some non-OpenPGP cruft glued to
> the end of it?
>
> David
>
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>



-- 
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