Re: [RFC][PATCH] Make cryptoapi non-optional?

David Wagner
2003-08-14T19:41:21Z

Val Henson wrote:
>Throwing away 80 bits of the 160 bit output is much better
>than folding the two halves together. In all the cases we've
>discussed where folding might improve matters, throwing away half the
>output would be even better.

I don't see where you are getting this from. Define
F(x) = first80bits(SHA(x))
G(x) = first80bits(SHA(x)) xor last80bits(SHA(x)).
What makes you think that F is a better (or worse) hash function than G?

I think there is little basis for discriminating between them.
If SHA is cryptographically secure, both F and G are fine.
If SHA is insecure, then all bets are off, and both F and G might be weak.