modexp
======

Modular exponentiation core for implementing public key algorithms such
as RSA, DH, ElGamal etc.

The core calculates the following functions:

  C = M ** e mod N
  M = C ** d mod N

  d is the private key exponent.
  M is a message with a length of n bits
  e is the exponent with a length of at most 32 bits
  N is the modulus  with a length of n bits
  n is can be 32 and up to and including 8192 bits in steps
  of 32 bits.

The core has a 32-bit memory like interface.

The core is written in Verilog 2001 and suitable for implementation in
FPGA and ASIC devices. No vendor specific macros are used in the code.


## Implementation details ##

The core is using Montgomery multiplication with 32-bit operands. The
core is iterative and will not be the fastest core on the
planet.

The core will perform blinding to protect against side channel
attacks.


## FPGA-results ##

No results yet.


## Status ##

***(2015-03-13)***

A working, bit exact C model with test cases has been developed and is
used to drive the HW development. There is also a Java functional model
available as support for high level undertanding.

Development of the Montgomery product module started. Top level modexp
module with memories for all operands are being worked on.