linux/lib/crypto/mpi/mpi-mod.c

/* mpi-mod.c -  Modular reduction
 * Copyright (C) 1998, 1999, 2001, 2002, 2003,
 *               2007  Free Software Foundation, Inc.
 *
 * This file is part of Libgcrypt.
 */


#include "mpi-internal.h"
#include "longlong.h"

/* Context used with Barrett reduction.  */
struct barrett_ctx_s { … };



void mpi_mod(MPI rem, MPI dividend, MPI divisor)
{ … }

/* This function returns a new context for Barrett based operations on
 * the modulus M.  This context needs to be released using
 * _gcry_mpi_barrett_free.  If COPY is true M will be transferred to
 * the context and the user may change M.  If COPY is false, M may not
 * be changed until gcry_mpi_barrett_free has been called.
 */
mpi_barrett_t mpi_barrett_init(MPI m, int copy)
{ … }

void mpi_barrett_free(mpi_barrett_t ctx)
{ … }


/* R = X mod M
 *
 * Using Barrett reduction.  Before using this function
 * _gcry_mpi_barrett_init must have been called to do the
 * precalculations.  CTX is the context created by this precalculation
 * and also conveys M.  If the Barret reduction could no be done a
 * straightforward reduction method is used.
 *
 * We assume that these conditions are met:
 * Input:  x =(x_2k-1 ...x_0)_b
 *     m =(m_k-1 ....m_0)_b	  with m_k-1 != 0
 * Output: r = x mod m
 */
void mpi_mod_barrett(MPI r, MPI x, mpi_barrett_t ctx)
{ … }


void mpi_mul_barrett(MPI w, MPI u, MPI v, mpi_barrett_t ctx)
{ … }