[R] Help with decrypting

MacQueen, Don
Wed, 09 Nov 2016 18:11:46 -0000

Thanks, Marc,

Unfortunately, I didn't choose the encryption method. My (only) need is to
be able to decrypt an existing file that is maintained by others. I am able to
use system() on a simple perl script to do the job, but I'm hoping for an
R-only solution, primarily for portability.

-Don

--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062


From: Marc Schwartz <marc_schwartz at me.com<mailto:marc_schwartz at
me.com>>
Date: Monday, November 7, 2016 at 3:30 PM
To: dh m <macqueen1 at llnl.gov<mailto:macqueen1 at llnl.gov>>
Cc: R-help <R-help at r-project.org<mailto:R-help at r-project.org>>
Subject: Re: [R] Help with decrypting


On Nov 7, 2016, at 4:47 PM, MacQueen, Don <macqueen1 at
llnl.gov<mailto:macqueen1 at llnl.gov>> wrote:

I have a file containing encrypted contents. The contents can be decrypted
using perl, like this:

open (FILEHANDLE, "/path/to/file")
chomp ($ciphertext = <FILEHANDLE>);


use Crypt::CBC;
$cipher = Crypt::CBC->new( -key    => 'my secret key',
                          -cipher => 'Blowfish'
                         );

$plaintext  = $cipher->decrypt($ciphertext);


(See http://search.cpan.org/~lds/Crypt-CBC-2.33/CBC.pm)

M goal is to have the value of $plaintext in an R object, so, is there an
R equivalent to this decrypt() perl function?

I've found R packages
 bcrypt
 sodium
that appear to have potential, but I don't understand this business well
enough to figure out how to use them, if indeed they can be used, for
this. Help would be much appreciated.

Thanks
-Don



Hi Don,

Blowfish is Bruce Schneier's algorithm from the early 90's, which even
Bruce suggested some time ago not be used. Bruce has some alternative Blowfish
implementations available via his web site:

  https://www.schneier.com/academic/blowfish/download.html

and there is a link there for some third party products that still have it and
might provide for a CLI based interface as an alternative (e.g. GnuPG) if you
need to use it.

>From what I can tell, 'sodium' does not support Blowfish and the
implementation in bcrypt, if I am reading correctly, only provides for a one-way
hash implementation, as opposed to encrypt/decrypt functions.

Thus, barring that my searching for alternative R implementations of Blowfish
resulted in a Type II error, I do not see any R implementations of Blowfish that
support encrypt/decrypt.

If you want to use the Perl module implementation via R, you can take a look at
my WriteXLS package on GitHub:

  https://github.com/marcschwartz/WriteXLS

and see how I call Perl scripts within WriteXLS.R:

  https://github.com/marcschwartz/WriteXLS/blob/master/R/WriteXLS.R

around line 242.

That might provide one method for you.

That all being said, as per Bruce's recommendation, there are
"better" encryption/decryption algorithms these days (some in the
'digest' package by Dirk), depending upon who you are trying to protect
the data from... :-)

Regards,

Marc Schwartz



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