big number(around 100 digits) arithmetic

[ Please keep me in CC as I'm not subscribed to the list]

HI all,

I=E2=80=99m looking for a =E2=80=9CC=E2=80=9D program for big number(around=
 100 digits)
arithmetic i.e.
mltiplication\addition\division\subtraction\exponentiation and
modulus, etc.

Basically I want to use it for =E2=80=98Extended Euclidean Algorithm=E2=80=
=99 and
public-key encryption with the RSA algorithm which typically requires
larger integers and it will not fit into C data types. Can someone
point me the to the either source code or logical explanation on how
to handle big number arithmetic?

--=20
Thanks,
Sekhar