Date: Mon, 25 May 2009 23:57:00 +0100 From: RW <rwmaillists@googlemail.com> To: freebsd-questions@freebsd.org Subject: Re: Secure unsalted or fixed salt symmetric encryption? Message-ID: <20090525235700.5907deaf@gumby.homeunix.com> In-Reply-To: <20090525215205.GA45395@slackbox.xs4all.nl> References: <26face530905242257m7030933cy4a1171de7a06ee59@mail.gmail.com> <20090525190039.GA39139@slackbox.xs4all.nl> <20090525220601.1a9f7109@gumby.homeunix.com> <20090525215205.GA45395@slackbox.xs4all.nl>
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On Mon, 25 May 2009 23:52:05 +0200 Roland Smith <rsmith@xs4all.nl> wrote: > On Mon, May 25, 2009 at 10:06:01PM +0100, RW wrote: > > On Mon, 25 May 2009 21:00:39 +0200 > > Roland Smith <rsmith@xs4all.nl> wrote: > > > > > > > Or you can use the -nosalt option. But as explained in > > > [http://www.openssl.org/docs/apps/enc.html], using a random salt > > > by default is a design decision because: "Without the -salt > > > option it is possible to perform efficient dictionary attacks on > > > the password". That doesn't sound good, does it? > > > > It's not a problem since she's using a random key file, not a weak > > password. > > But a key alone is not sufficient. You'll need to specify an > initialization vector as well, using the -iv option. E.g.: > > openssl enc -aes256 -in <infile> -out <outfile>.aes \ > -K 971001EE50DCDBCAF3F521851E773B0285838CA549E2258C1A195565D61F2145 \ > -iv FD246E34A631AE38 > > If you try it with only a key or keyfile, you'll get a 'iv undefined' > error, resulting in a zero-length output file. :-( > It works for me: $ echo "hello world" > infile $ head -c32 /dev/random |sha256 > keyfile $ openssl enc -aes256 -nosalt -kfile keyfile -in infile -out outfile $ openssl enc -aes256 -nosalt -d -kfile keyfile -in outfile hello world
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