diff --git a/programs/pkey/mpi_demo.c b/programs/pkey/mpi_demo.c
new file mode 100644
index 0000000..699fa5a
--- /dev/null
+++ b/programs/pkey/mpi_demo.c
@@ -0,0 +1,76 @@
+/*
+ *  Simple MPI demonstration program
+ *
+ *  Copyright (C) 2006-2007  Christophe Devine
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef _CRT_SECURE_NO_DEPRECATE
+#define _CRT_SECURE_NO_DEPRECATE 1
+#endif
+
+#include <stdio.h>
+
+#include "xyssl/bignum.h"
+
+int main( void )
+{
+    mpi E, P, Q, N, H, D, X, Y, Z;
+
+    mpi_init( &E, &P, &Q, &N, &H,
+              &D, &X, &Y, &Z, NULL );
+
+    mpi_read_string( &P, 10, "2789" );
+    mpi_read_string( &Q, 10, "3203" );
+    mpi_read_string( &E, 10,  "257" );
+    mpi_mul_mpi( &N, &P, &Q );
+
+    printf( "\n  Public key:\n\n" );
+    mpi_write_file( "  N = ", &N, 10, NULL );
+    mpi_write_file( "  E = ", &E, 10, NULL );
+
+    printf( "\n  Private key:\n\n" );
+    mpi_write_file( "  P = ", &P, 10, NULL );
+    mpi_write_file( "  Q = ", &Q, 10, NULL );
+
+    mpi_sub_int( &P, &P, 1 );
+    mpi_sub_int( &Q, &Q, 1 );
+    mpi_mul_mpi( &H, &P, &Q );
+    mpi_inv_mod( &D, &E, &H );
+
+    mpi_write_file( "  D = E^-1 mod (P-1)*(Q-1) = ",
+                    &D, 10, NULL );
+
+    mpi_read_string( &X, 10, "55555" );
+    mpi_exp_mod( &Y, &X, &E, &N, NULL );
+    mpi_exp_mod( &Z, &Y, &D, &N, NULL );
+
+    printf( "\n  RSA operation:\n\n" );
+    mpi_write_file( "  X (plaintext)  = ", &X, 10, NULL );
+    mpi_write_file( "  Y (ciphertext) = X^E mod N = ", &Y, 10, NULL );
+    mpi_write_file( "  Z (decrypted)  = Y^D mod N = ", &Z, 10, NULL );
+    printf( "\n" );
+
+    mpi_free( &Z, &Y, &X, &D, &H,
+              &N, &Q, &P, &E, NULL );
+
+#ifdef WIN32
+    printf( "  Press Enter to exit this program.\n" );
+    fflush( stdout ); getchar();
+#endif
+
+    return( 0 );
+}