Re: [TLS] DSS with other than SHA-1 algorithms

[Nikos Mavrogiannopoulos <[e-mail]>]

On Thu, Feb 10, 2011 at 9:11 AM, Nikos Mavrogiannopoulos
<[e-mail]> wrote:
> Hello,
>  According to FIPS-186-3 the DSA algorithm might
> be used with hashes other than SHA-1. Moreover
> it mentions:
> "A hash function that provides a lower security strength than the (L, N)
> pair ordinarily should not be used, since this would reduce the
> security strength of the digital signature process to a level no greater
> than that provided by the hash function."
[...]
> For TLS 1.2 I suppose that the hash being negotiated
> by the signature algorithm extension will be used,
> and if it is larger than N, then it will be truncated.

I've tried to clarify a bit the issues and make a "best
current practice text":
http://homes.esat.kuleuven.be/~nikos/draft-mavrogiannopoulos-tls-dss.txt

Does this clarification match with what other implementations
have done in supporting DSA? (in gnutls for example we didn't
truncate the hash, if a larger hash was available to be selected, but
rather use the next available...), Would be better if truncation be
avoided at all?

regards,
Nikos