First of all, sorry for a late posting on this issue (i was on vacation and
just
caught it). Now: in his message of 02/22/02 6:46 AM, albert.mietus says:

>> Is MD5 really that much faster than SHA1? (MD5 has known problems
>> and there are RFC's saying not to use it)

> Yes, MD5 for hashing should be at least twice as fast. However hashing
> isn't
> the bottleneck
Agreed. Hashing is the least problem, since any good hashing algorithm is
way
faster than a symmetric cipher.

[snip]

> But, his first suggestions, as alternatives to SHA1/DSA are:
>  1) SHA1 with RSA             RSA is a lot faster then DSA
>  2) MD5  with RSA             MD5 & RSA are faster:  quite fast
>  3) DES in CBC mode           very fast
>        This (3) gives a MAC not a signature (see note 1)

(3) should be discarded as it does not provide a valid signature, i.e.,
it does not have non-repudiation properties.
A fast and compact scheme, providing also low resource consumption so to
be used in lightweight devices (as light as a smartcard, btw), is achieved
by using elliptic curves, e.g. EC-DSA (ANSI X9.62), see FIPS 186-2. A scheme
implementing SHA-1 with EC-DSA will be the fastest option.

> Alternative 3 should be the fastest one. Alternative 1 is faster then
> SHA1/DSA, but hardly used because alt-2 is better (faster) at no cost.

Except for the collision effects in MD5, besides the fact that MD5's 
hash length makes it non-recommendable for environments with many
messages (as the case is).

[snip]

> Not quite. The problems with WEP are not due to the algorithm (witch is
> MD5
> it think), but a "bug" in the design.
WEP uses RC4, which has its own weaknesses besides the design flaw of the
cryptosystem.

[snip]

Regards,

Enrique

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