Date: Mon, 25 May 2009 23:52:05 +0200 From: Roland Smith <rsmith@xs4all.nl> To: RW <rwmaillists@googlemail.com> Cc: freebsd-questions@freebsd.org Subject: Re: Secure unsalted or fixed salt symmetric encryption? Message-ID: <20090525215205.GA45395@slackbox.xs4all.nl> In-Reply-To: <20090525220601.1a9f7109@gumby.homeunix.com> References: <26face530905242257m7030933cy4a1171de7a06ee59@mail.gmail.com> <20090525190039.GA39139@slackbox.xs4all.nl> <20090525220601.1a9f7109@gumby.homeunix.com>
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--opJtzjQTFsWo+cga Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable 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: >=20 >=20 > > 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? >=20 > 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. :-( If you use a password (-pass) you don't need an iv. Roland --=20 R.F.Smith http://www.xs4all.nl/~rsmith/ [plain text _non-HTML_ PGP/GnuPG encrypted/signed email much appreciated] pgp: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 (KeyID: C321A725) --opJtzjQTFsWo+cga Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.11 (FreeBSD) iEYEARECAAYFAkobEwUACgkQEnfvsMMhpyW6ewCgg2Y7n2+YDvlZO5H/jfYgL6vV GpQAoKZp6F4Ojrv36rDF6FLTYfcix/vY =ksp5 -----END PGP SIGNATURE----- --opJtzjQTFsWo+cga--
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