[racket] string->bytes/locale on an HMAC-SHA1 hash returns error

Hi Norman,

Thanks, that looks great.  I'll give it a shot.

Shawn

On Mon, May 14, 2012 at 2:23 AM, Norman Gray <norman at astro.gla.ac.uk> wrote:

>
> Shawn, hello.
>
> On 2012 May 14, at 09:12, Shawn Smith wrote:
>
> > I guess I've tracked the problem down to the fact that the Racket hash is
> > not a digest.
>
> I think it is, but the problem is that you're not displaying the resulting
> byte string correctly.
>
> > echo -n "foo" | openssl dgst -sha1 -hmac "privatekey"
> >
> > I get what I'm looking for, a 40 character hex hash:
> >
> > 6d1198d3c8770f2409c6b73ed11af9d2076e4588
> >
> > I'm not sure how to get Racket to do this as well.  Does anyone know?
>
> (require web-server/stuffers/hmac-sha1
>         file/sha1) ; or openssl/sha1
>
> (bytes->hex-string (HMAC-SHA1 #"privatekey" #"foo"))
>
> => "6d1198d3c8770f2409c6b73ed11af9d2076e4588"
>
> HMAC-SHA1 produces the result as a byte string (which is different from a
> string).  Base-64 encoding writes out that string of bytes in a form which
> can be safely mailed -- that's not what you want.
>
> Instead, bytes->hex-string formats each byte in the string as a two-digit
> hex number, resulting in a string.
>
> All the best,
>
> Norman
>
>
> --
> Norman Gray  :  http://nxg.me.uk
> SUPA School of Physics and Astronomy, University of Glasgow, UK
>
>
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