Hello,
Is this a known bug, am I doing something wrong, or maybe it's even a
feature that I don't understand?
When encrypting a file that starts with 4 binary 0 bytes then gnupg does
not automatically compress it (you'd have to explicitely specify -z6,
which normally is the default).
Anything else gets compressed fine. Please have a look at the examples
below...
I'm using GnuPG v1.0.7 on a 32bit x86 Linux system.
Example #1. File looks like: <3 times 0><1001 times 1>
GnuPG DOES compress this file (as it should be!).
max at scotty:/tmp$ perl -e 'print "\0"x3' > file
max at scotty:/tmp$ perl -e 'print "\1"x1001' >> file
max at scotty:/tmp$ gpg -r markus --encrypt file
max at scotty:/tmp$ gpg --list-packets file.gpg
:pubkey enc packet: version 3, algo 1, keyid 661C7ADBE6401E5B
data: [4095 bits]
You need a passphrase to unlock the secret key for
user: "Markus Stoeger <markus_stoeger at gmx.at>"
4096-bit RSA key, ID E6401E5B, created 2002-05-01 (main key ID 5514D918)
:encrypted data packet:
length: 67
^^-- looks compressed!
mdc_method: 2
gpg: encrypted with 4096-bit RSA key, ID E6401E5B, created 2002-05-01
"Markus Stoeger <markus_stoeger at gmx.at>"
:compressed packet: algo=2
^^^^^^^^^^^^^^^^^^^^^^^^^^-- all ok!
:literal data packet:
mode b, created 1032104276, name="file",
raw data: 1004 bytes
Example #2. File looks like: <4 times 0><1000 times 1>
GnuPG does NOT compress this file.
max at scotty:/tmp$ perl -e 'print "\0"x4' > file
max at scotty:/tmp$ perl -e 'print "\1"x1000' >> file
max at scotty:/tmp$ gpg -r markus --encrypt file
max at scotty:/tmp$ gpg --list-packets file.gpg
:pubkey enc packet: version 3, algo 1, keyid 661C7ADBE6401E5B
data: [4096 bits]
You need a passphrase to unlock the secret key for
user: "Markus Stoeger <markus_stoeger at gmx.at>"
4096-bit RSA key, ID E6401E5B, created 2002-05-01 (main key ID 5514D918)
:encrypted data packet:
length: 1027
^^^^-- no compression here...
mdc_method: 2
gpg: encrypted with 4096-bit RSA key, ID E6401E5B, created 2002-05-01
"Markus Stoeger <markus_stoeger at gmx.at>"
??????????????????????????-- no compression here...
:literal data packet:
mode b, created 1032104224, name="file",
raw data: 1004 bytes
:mdc packet: length=20