To tar and compress a directory, then encrypt it with the AES algorithm:
tar -czf - [directory] | gpg -c --cipher-algo AES -o [directory].tgz.gpg
You will be prompted to input a password.
To decrypt, decompress and untar:
gpg -d [directory].tgz.gpg | tar -xzf -
To can see a list of available cipher algorithms:
gpg --version
If you do not specify a cipher algorithm that uses MDC by default (like AES), gpg will default to encrypting using the CAST5 algorithm and you will get a warning message when you decrypt:
gpg: CAST5 encrypted data gpg: encrypted with 1 passphrase gpg: WARNING: message was not integrity protected
Example
steph@slap ~/tmp/gpgtest $ ls -l
total 0
drwxr-xr-x 2 steph users 80 2008-09-27 17:35 testdir
steph@slap ~/tmp/gpgtest $ ls -l testdir/
total 4
-rw-r--r-- 1 steph users 20 2008-09-27 17:34 test1.txt
steph@slap ~/tmp/gpgtest $ cat testdir/test1.txt
testing testing 123
steph@slap ~/tmp/gpgtest $ tar -czf - testdir | gpg -c --cipher-algo AES -o testdir.tgz.gpg
steph@slap ~/tmp/gpgtest $ rm -rf testdir
steph@slap ~/tmp/gpgtest $ ls -l
total 4
-rw-r--r-- 1 steph users 236 2008-09-27 17:36 testdir.tgz.gpg
steph@slap ~/tmp/gpgtest $ gpg -d testdir.tgz.gpg | tar -xzf -
gpg: AES encrypted data
gpg: encrypted with 1 passphrase
steph@slap ~/tmp/gpgtest $ ls -l
total 4
drwxr-xr-x 2 steph users 80 2008-09-27 17:35 testdir
-rw-r--r-- 1 steph users 236 2008-09-27 17:36 testdir.tgz.gpg
steph@slap ~/tmp/gpgtest $ ls -l testdir
total 4
-rw-r--r-- 1 steph users 20 2008-09-27 17:34 test1.txt
steph@slap ~/tmp/gpgtest $ cat testdir/test1.txt
testing testing 123
