Bignum modular types in Ada95

[Markus Kuhn <Markus.Kuhn@cl.cam.ac.uk>]

One of the especially nice things about Ada seem to be the modular
types. Many of the calculations in asymmetric cryptography are done
over the integers modulo N, where N is a huge number (typically
1024 bits long or more).

I wonder how many Ada compilers support bignum arithmetic directly
without any special library calls, as in

  type Unsigned1024 is range 0..2**1024-1;
  Modulus, Public_Key: Unsigned1024;
  type Message is mod Modulus;
  Clear_Text, Cipher_Text: Message;

  Cipher_Text := Clear_Text ** Public_Key;

Considering that the next generation of server processors
will feature 1024-bit registers and hardware for fast modular
exponentiation, it is nice to know that Ada95 has already the
language constructs available today to use these forthcoming
capabilities comfortably. Neither C nor Java has. I wonder
however, whether existing Ada95 compilers for existing processors
do already support bignum modular arithmetic in a (certainly
slower) software emulation. If not, bignum arithmetic would not be
a portable feature and would therefore be of limited use once
the crypto-coprocessor with suitable hardware registers and
ALUs become available.

Which Ada95 compilers do support 1024-bit integers today and can
do an efficient modular exponentiation over them?

Markus

-- 
Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK
email: mkuhn at acm.org,  home page: <http://www.cl.cam.ac.uk/~mgk25/>