Big_int a^x mod m

Big_int a^x mod m

[Julian Assange]

 val (**/) : num -> num -> num 
 val power_num : num -> num -> num
   Exponentiation

The num library documentation doesn't seem to support modular
exponentiation. This is seems to be an unusual oversight, and means
the library isn't useful for real-world cryptographic applications.

Is anyone working on adding mod exp's? Or are there other bigint
ocaml libraries?

Cheers,
Julian.

Re: Big_int a^x mod m

[Remi VANICAT]

Julian Assange <proff@iq.org> writes:

>  val (**/) : num -> num -> num 
>  val power_num : num -> num -> num
>    Exponentiation
> 
> The num library documentation doesn't seem to support modular
> exponentiation. This is seems to be an unusual oversight, and means
> the library isn't useful for real-world cryptographic applications.
> 
> Is anyone working on adding mod exp's? Or are there other bigint
> ocaml libraries?

there is at least two other bigint libraries :
one is MLGMP a binding for GNU MP :
  http://www.di.ens.fr/~monniaux/programmes.html.en 
the other is numerix : http://pauillac.inria.fr/~quercia/

-- 
Rémi Vanicat
vanicat@labri.u-bordeaux.fr
http://dept-info.labri.u-bordeaux.fr/~vanicat

Re: Big_int a^x mod m

[Michel Quercia]

Le Mon, 24 Jul 2000, Remi VANICAT a écrit :
> Julian Assange <proff@iq.org> writes:

> > Is anyone working on adding mod exp's? Or are there other bigint
> > ocaml libraries?
>
> there is at least two other bigint libraries :
> one is MLGMP a binding for GNU MP :
>   http://www.di.ens.fr/~monniaux/programmes.html.en 
> the other is numerix : http://pauillac.inria.fr/~quercia/

As GMP has such a function, MLGMP should have a binding for it (I can't swear as
I haven't the docs here). My own library, numerix, has no builtin modular
exponentiation, but you'll find one in the examples (file
exemples/nextpp/ocaml/nextpp.ml, lines 54-64). It may go into the core
library in a future release.

-- 
Michel Quercia
23 rue de Montchapet, 21000 Dijon
http://pauillac.inria.fr/~quercia
mailto:quercia@cal.enst.fr

Re: Big_int a^x mod m

[Julian Assange]

Julian Assange <proff@iq.org> writes:

>  val (**/) : num -> num -> num 
>  val power_num : num -> num -> num
>    Exponentiation
> 
> The num library documentation doesn't seem to support modular
> exponentiation. This is seems to be an unusual oversight, and means
> the library isn't useful for real-world cryptographic applications.
> 
> Is anyone working on adding mod exp's? Or are there other bigint
> ocaml libraries?

Following this up, there is the fast Numerix library, an extended
replacement for Big_int, which also contains a subset of bindings to
libgmp (Numerix native code is usally faster than gmp2.x -- but it's
worth noting that gmp3.0 has recently been released).

It would be nice to see this library replace Big_int entirely,
with wrappers for for backwards compatability.

Unfortunately Numerix doesn't support modular exponents either,
although it does support a lot of other nice operations that Big_int
does not, and is well structured.

Numerix, btw is not listed either in the Hump or in Gerd's O'Caml
link database.

But you can find it here:

    http://pauillac.inria.fr/~quercia/

There is also a naive libgmp ocaml wrapper:

   http://www.di.ens.fr/~monniaux/download/mlgmp_0.13.tar.gz  

Which *does* contain bindings to the gmp modular exponentiation
functions mpz_powm and mpz_powm_ui.

Cheers,
Julian.