Re: libscrypt

[Solar Designer <solar@openwall.com>]

Hi all,

What's the current status on a libscrypt?  I will likely try optimizing
the scrypt code (in fact, I've already played with that a bit) and then
revising it (deviating from scrypt proper).  Indeed, it'd be convenient
to be doing that with a libscrypt rather than with the scrypt file
encryption program - and ultimately I'll need a library rather than a
standalone program (in fact, I'd need to have scrypt's memory allocation
split from the actual crypto).  Obviously, I'd want to contribute back
whatever is relevant.

On Sun, Jan 08, 2012 at 02:58:52PM -0800, Colin Percival wrote:
> On 01/03/12 09:40, Dan Kaminsky wrote:
> >    I just released phidelius, which basically uses the output of scrypt's PRNG
> > to feed /dev/random and the like.  Go to dankaminsky.com/phidelius
> > <http://dankaminsky.com/phidelius> to see why I'd do such a horrifying thing.
> 
> Cool. :-)

I took a look at Dan's phidelius-1.01 as downloaded from:

http://s3.amazonaws.com/dmk/phidelius-1.01.tgz

It contains a verbatim copy of scrypt-1.1.6 plus more files (specific to
Phidelius).  It does not turn scrypt into a library, but it does show
how the existing scrypt code can be linked to and invoked.

I also found an actual libscrypt, under that name even, as part of
Chromium OS:

http://git.chromium.org/gitweb/?p=chromiumos/third_party/libscrypt.git
git clone http://git.chromium.org/chromiumos/third_party/libscrypt.git

This one has a verbatim copy of scrypt-1.1.6 under libscrypt/src, and it
adds autofiles at top level to build a library.  It appears to always
use the slower crypto_scrypt-ref.c code.

There's also Crypt-Scrypt in CPAN, which reuses Chromium OS libscrypt:

http://search.cpan.org/~gray/Crypt-Scrypt/
https://github.com/gray/crypt-scrypt

Finally, there's Simon's modscrypt, which is a hack of the scrypt
program to make it print the test vectors instead of doing what it does
normally:

https://www.gitorious.org/scrypt/modscrypt
git clone git://gitorious.org/scrypt/modscrypt.git

The only changes are:

$ diff -urx .git scrypt-1.1.6 modscrypt | diffstat
 lib/crypto/crypto_scrypt-nosse.c |   13 +++++++++++++
 lib/crypto/crypto_scrypt-sse.c   |   13 +++++++++++++
 main.c                           |   30 ++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+)

(somehow the -ref file is not patched to print the test vectors as well)

modscrypt is not a library, yet it may be useful for my testing too.

> I've attached the autocrap files.

Would it be better to start with these or with those from Chromium OS?

BTW, earlier today I found that scrypt mailing list archive is finally
available via the web.  Here's the message I am replying to:

http://mail.tarsnap.com/scrypt/msg00035.html

> BTW, I'm planning on adding scrypt to Google
> code soon (to join kivaloo, spiped, and libcperciva, with which it shares some
> code).

What's the status on this?

Thanks,

Alexander