[PLUG] Command to encrypt files

[Martin A. Brown]

> My OS: Mint Linux 16

> New member here. I would like to know if there is a command to 
> encrypt files? I thought it was "crypt" but I see that is in 
> section 3 of the man pages, meaning it's a programming function.

I'm a command-line monster, so I would reach first for 'gpg'.  It's 
part of the 'gnupg' package.  I had a PDF hanging around in my home 
directory, and am using that as an example file below. These two 
commands do the same thing, just that one of them allows you to 
explicitly name the output file.  Regardless of the invocation, you 
will be prompted to type the encryption passphrase twice.

   gpg --output W472242.PDF.gpg --symmetric -- W472242.PDF
   gpg --symmetric -- W472242.PDF

Then, to recover your data, you would decrypt as follows.

   gpg --output W472242.PDF.aaa --decrypt -- W472242.PDF.gp
   gpg --decrypt -- W472242.PDF.gpg  > W472242.PDF.bbb

And, to verify that the encryption and decryption worked, you can 
see that I used the 'md5sum' utility to get a checksum of my data 
before and after.

   $ md5sum  W472242.PDF*
   c787744f66f790efeef893016c4ad587  W472242.PDF
   c787744f66f790efeef893016c4ad587  W472242.PDF.aaa
   c787744f66f790efeef893016c4ad587  W472242.PDF.bbb
   f464112b24fe58c06f5a6f2eab6d7e2a  W472242.PDF.gpg

Note that gpg can also handle public-key cryptography (which 
involves key-pairs) in addition to the simpler encryption shown 
above.  It is called symmetric, because you use the same passphrase 
for encryption as for decryption.

-Martin

-- 
Martin A. Brown
http://linux-ip.net/