OK, I see.  There's a line feed in the string I'm hashing with sha256sum
and, of course, there isn't one in my simple sample.  Drat!  I'm not sure
when I would have seen that on my own.

At least that answers my question: there should NOT be any difference
between the output of sha256sum and the Cryptopp::SHA256().CalculateDigest
function.  Sanity has been restored.

 -ap

On Sat, 21 Apr 2012, Geoff Beier wrote:

> On Sat, Apr 21, 2012 at 14:29, Alan Partis <[email protected]> wrote:
> > $ echo this |sha256sum
> >
> > produces a 32-byte hex string "c18d ..."
> >
> > On the other hand, when I pass a 32-byte message buffer containing "this"
> > followed by 28 nulls as follows:
> >
> >  CryptoPP::SHA256().CalculateDigest(digest, msg, 4)
> >
> > I get an output digest containing a 32-byte hex string "1e87 ..."
>
> You mean like this?
>
> $ echo this |openssl dgst -sha256
> c18d547cafb43e30a993439599bd08321bea17bfedbe28b13bce8a7f298b63a2
> $ echo -n this |openssl dgst -sha256
> 1eb79602411ef02cf6fe117897015fff89f80face4eccd50425c45149b148408
>
> As the last reply pointed out, pay attention to the -n.
>
> On my system, the first is hashing 5 bytes:
> 0x74, 0x68, 0x69, 0x73, 0x0A
> while the second is hashing the 4 bytes
> 0x74, 0x68, 0x69, 0x73
>
> HTH,
>
> Geoff

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