SHA1 - set initial key/state?

[Nick Aschberger]

Hi Folks,

I may be missing something in my use of the SHA1 algorithm, I am
hoping you can explain it to me.

I have an unencrypted string, I make a function call like:
my_sha1_object.calculateDigest(outputdigest, inputstring, length);

No problems there, my digest is created.


However, I am sending this information across a socket, so I'm
thinking that anyone can snoop my unencrypted string,
and assuming they were also using cryptopp sha algorithm, they would
easily be able to recreate the same digest.

Am I wrong in thinking this is insecure - am I thinking about this
incorrectly?

I've been wondering if there is some way to initialise the "state" of
the sha object with our own key/values, which would be secure, and
unrepeatable.

I have looked in to the sha1.InitState function - this retrieves the
intial state - but how do you set it?

Is the "transform" function what I am after? There is no documentation/
usage guide/examples or even comments (or my google-fu is weak!) for
either InitState or Transform functions.
So, what are they for, and do they do what I want?

thanks!

Nick Aschberger

[Jeffrey Walton]

Hi Nick,

Use an HMAC.

Jeff

[Nick Aschberger]

Oh.... duh. It's so simple!

Thanks Jeff.

On Jun 25, 4:29 pm, Jeffrey Walton <noloa...@gmail.com> wrote:
> Hi Nick,
>
> Use an HMAC.
>
> Jeff
>