[Novalug] how to lock a file with a key

[Rob Payne]

On Wed, Feb 20, 2008 at 07:03:35PM -0500, Nino Pereira wrote:
> A simple question for security experts:
> 
> I'd like to scramble a file, send it by email,
> and then unscamble it at the other end. I'd like
> it to be scrambled with a key, which only I know,
> so that I can unscramble it at the other end with
> this same key.
> 
> Any earlier discussion about hashes and md5 and such
> mostly went by me because I didn't expect to ever want to do
> this, but now that I do I can't remember what to google for.
> 
> Any suggestions?

Nino,

There are many types of encryption.  Depending upon what tools you
have available, how much you want to protect the file contents, the
methods you have available to protect the keying material, etc. there
are many different choices of encryption.  Hashes are one-way,
creating a hash of a file does not let you get the file back from the
hash.

There is probably more than you ever wanted to know about cryptology
is available: http://en.wikipedia.org/wiki/Cryptology

Here are some instructions on doing what you want to do, with gpg:

http://www.cyberciti.biz/tips/linux-how-to-encrypt-and-decrypt-files-with-a-password.html

Be paranoid! :)

				 -rob
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