[Authentication] Fwd: Re: Session negotiation

[Michael Leupold]

On Thursday 16 July 2009 01:46:17 Stef Walter wrote:
> Michael Leupold wrote:
> > I imagined the IV to be transmitted once during negotiation. The
> > constructed cipher would then be used in streaming mode. As far as I
> > understand it we wouldn't need to retransmit the iv as the service as
> > well as the client would just keep some handle to an encryption struct
> > around (eg. gcry_cipher_hd_t for gcrypt). Please tell me if I'm
> > completely getting this wrong.
>
> An IV can never be reused. Doing so, especially with short data like
> secrets a big security hole.

I wasn't talking about reuse, I was more or less considering the secrets to be 
passed through a stream cipher that whose state was established on session 
start. After trying I figured it's not the right approach though as while the 
same secret encrypted over and over produces different encrypted results they 
have to be manually padded/unpadded as apparently crypto libraries only 
support padding on the last block encrypted (at least libqca does).

So yeah, we'll need the iv as parameter.

Regards,
Michael

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