Weaknesses in SHA-1

[Thomas Sjögren]

On Sat, Oct 02, 2004 at 02:56:27AM -0400, Atom 'Smasher' wrote:
> with all this talk of (allegedly!) weak and broken hashes, i'd like to 
> throw out a construct to combine 2 or more hashes and (it seems) make the 
> construct more secure than either one of the hashes independently: take 
> two or more hashes and XOR them.

And this creates what? Neither a sha1 or ripemed verification is
possible.

r = H(H(M))

or

H' = H(M)
H' -> H1,H2
H" = H(H1 xor H2)  
r = H(H")

seems to me are better options, the first obviously faster than the
second. 
the security improvements? none i guess if you're using anything else
than md5 or sha{0,1}.

/Thomas
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