[R] Help with decrypting

Marc Schwartz marc_schwartz at me.com
Tue Nov 8 00:30:42 CET 2016

> On Nov 7, 2016, at 4:47 PM, MacQueen, Don <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 <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 <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 <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... :-)


Marc Schwartz

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