/* $OpenBSD: bn_nist.c,v 1.22 2022/07/31 14:38:38 jsing Exp $ */
/*
 * Written by Nils Larsch for the OpenSSL project
 */
/* ====================================================================
 * Copyright (c) 1998-2005 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include <endian.h>
#include <stdint.h>
#include <string.h>

#include "bn_lcl.h"

#define CTASSERT(x)     extern char  _ctassert[(x) ? 1 : -1 ]   \
                            __attribute__((__unused__))

#define BN_NIST_192_TOP (192+BN_BITS2-1)/BN_BITS2
#define BN_NIST_224_TOP (224+BN_BITS2-1)/BN_BITS2
#define BN_NIST_256_TOP (256+BN_BITS2-1)/BN_BITS2
#define BN_NIST_384_TOP (384+BN_BITS2-1)/BN_BITS2
#define BN_NIST_521_TOP (521+BN_BITS2-1)/BN_BITS2

/* pre-computed tables are "carry-less" values of modulus*(i+1) */
#if BN_BITS2 == 64
static const BN_ULONG _nist_p_192[][BN_NIST_192_TOP] = {
        {0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFEULL, 0xFFFFFFFFFFFFFFFFULL},
        {0xFFFFFFFFFFFFFFFEULL, 0xFFFFFFFFFFFFFFFDULL, 0xFFFFFFFFFFFFFFFFULL},
        {0xFFFFFFFFFFFFFFFDULL, 0xFFFFFFFFFFFFFFFCULL, 0xFFFFFFFFFFFFFFFFULL}
};
static const BN_ULONG _nist_p_192_sqr[] = {
        0x0000000000000001ULL, 0x0000000000000002ULL, 0x0000000000000001ULL,
        0xFFFFFFFFFFFFFFFEULL, 0xFFFFFFFFFFFFFFFDULL, 0xFFFFFFFFFFFFFFFFULL
};
static const BN_ULONG _nist_p_224[][BN_NIST_224_TOP] = {
        {
                0x0000000000000001ULL, 0xFFFFFFFF00000000ULL,
                0xFFFFFFFFFFFFFFFFULL, 0x00000000FFFFFFFFULL
        },
        {
                0x0000000000000002ULL, 0xFFFFFFFE00000000ULL,
                0xFFFFFFFFFFFFFFFFULL, 0x00000001FFFFFFFFULL
        } /* this one is "carry-full" */
};
static const BN_ULONG _nist_p_224_sqr[] = {
        0x0000000000000001ULL, 0xFFFFFFFE00000000ULL,
        0xFFFFFFFFFFFFFFFFULL, 0x0000000200000000ULL,
        0x0000000000000000ULL, 0xFFFFFFFFFFFFFFFEULL,
        0xFFFFFFFFFFFFFFFFULL
};
static const BN_ULONG _nist_p_256[][BN_NIST_256_TOP] = {
        {
                0xFFFFFFFFFFFFFFFFULL, 0x00000000FFFFFFFFULL,
                0x0000000000000000ULL, 0xFFFFFFFF00000001ULL
        },
        {
                0xFFFFFFFFFFFFFFFEULL, 0x00000001FFFFFFFFULL,
                0x0000000000000000ULL, 0xFFFFFFFE00000002ULL
        },
        {
                0xFFFFFFFFFFFFFFFDULL, 0x00000002FFFFFFFFULL,
                0x0000000000000000ULL, 0xFFFFFFFD00000003ULL
        },
        {
                0xFFFFFFFFFFFFFFFCULL, 0x00000003FFFFFFFFULL,
                0x0000000000000000ULL, 0xFFFFFFFC00000004ULL
        },
        {
                0xFFFFFFFFFFFFFFFBULL, 0x00000004FFFFFFFFULL,
                0x0000000000000000ULL, 0xFFFFFFFB00000005ULL
        },
};
static const BN_ULONG _nist_p_256_sqr[] = {
        0x0000000000000001ULL, 0xFFFFFFFE00000000ULL,
        0xFFFFFFFFFFFFFFFFULL, 0x00000001FFFFFFFEULL,
        0x00000001FFFFFFFEULL, 0x00000001FFFFFFFEULL,
        0xFFFFFFFE00000001ULL, 0xFFFFFFFE00000002ULL
};
static const BN_ULONG _nist_p_384[][BN_NIST_384_TOP] = {
        {
                0x00000000FFFFFFFFULL, 0xFFFFFFFF00000000ULL,
                0xFFFFFFFFFFFFFFFEULL, 0xFFFFFFFFFFFFFFFFULL,
                0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL
        },
        {
                0x00000001FFFFFFFEULL, 0xFFFFFFFE00000000ULL,
                0xFFFFFFFFFFFFFFFDULL, 0xFFFFFFFFFFFFFFFFULL,
                0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL
        },
        {
                0x00000002FFFFFFFDULL, 0xFFFFFFFD00000000ULL,
                0xFFFFFFFFFFFFFFFCULL, 0xFFFFFFFFFFFFFFFFULL,
                0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL
        },
        {
                0x00000003FFFFFFFCULL, 0xFFFFFFFC00000000ULL,
                0xFFFFFFFFFFFFFFFBULL, 0xFFFFFFFFFFFFFFFFULL,
                0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL
        },
        {
                0x00000004FFFFFFFBULL, 0xFFFFFFFB00000000ULL,
                0xFFFFFFFFFFFFFFFAULL, 0xFFFFFFFFFFFFFFFFULL,
                0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL
        },
};
static const BN_ULONG _nist_p_384_sqr[] = {
        0xFFFFFFFE00000001ULL, 0x0000000200000000ULL, 0xFFFFFFFE00000000ULL,
        0x0000000200000000ULL, 0x0000000000000001ULL, 0x0000000000000000ULL,
        0x00000001FFFFFFFEULL, 0xFFFFFFFE00000000ULL, 0xFFFFFFFFFFFFFFFDULL,
        0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL
};
static const BN_ULONG _nist_p_521[] = {
        0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL,
        0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL,
        0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL, 0x00000000000001FFULL
};
static const BN_ULONG _nist_p_521_sqr[] = {
        0x0000000000000001ULL, 0x0000000000000000ULL, 0x0000000000000000ULL,
        0x0000000000000000ULL, 0x0000000000000000ULL, 0x0000000000000000ULL,
        0x0000000000000000ULL, 0x0000000000000000ULL, 0xFFFFFFFFFFFFFC00ULL,
        0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL,
        0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL, 0xFFFFFFFFFFFFFFFFULL,
        0xFFFFFFFFFFFFFFFFULL, 0x000000000003FFFFULL
};
#elif BN_BITS2 == 32
static const BN_ULONG _nist_p_192[][BN_NIST_192_TOP] = {
        {
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFE, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF
        },
        {
                0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFD, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF
        },
        {
                0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFC, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF
        }
};
static const BN_ULONG _nist_p_192_sqr[] = {
        0x00000001, 0x00000000, 0x00000002, 0x00000000, 0x00000001, 0x00000000,
        0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
};
static const BN_ULONG _nist_p_224[][BN_NIST_224_TOP] = {
        {
                0x00000001, 0x00000000, 0x00000000, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
        },
        {
                0x00000002, 0x00000000, 0x00000000, 0xFFFFFFFE,
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
        }
};
static const BN_ULONG _nist_p_224_sqr[] = {
        0x00000001, 0x00000000, 0x00000000, 0xFFFFFFFE,
        0xFFFFFFFF, 0xFFFFFFFF, 0x00000000, 0x00000002,
        0x00000000, 0x00000000, 0xFFFFFFFE, 0xFFFFFFFF,
        0xFFFFFFFF, 0xFFFFFFFF
};
static const BN_ULONG _nist_p_256[][BN_NIST_256_TOP] = {
        {
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000000,
                0x00000000, 0x00000000, 0x00000001, 0xFFFFFFFF
        },
        {
                0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000001,
                0x00000000, 0x00000000, 0x00000002, 0xFFFFFFFE
        },
        {
                0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000002,
                0x00000000, 0x00000000, 0x00000003, 0xFFFFFFFD
        },
        {
                0xFFFFFFFC, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000003,
                0x00000000, 0x00000000, 0x00000004, 0xFFFFFFFC
        },
        {
                0xFFFFFFFB, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000004,
                0x00000000, 0x00000000, 0x00000005, 0xFFFFFFFB
        },
};
static const BN_ULONG _nist_p_256_sqr[] = {
        0x00000001, 0x00000000, 0x00000000, 0xFFFFFFFE,
        0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFE, 0x00000001,
        0xFFFFFFFE, 0x00000001, 0xFFFFFFFE, 0x00000001,
        0x00000001, 0xFFFFFFFE, 0x00000002, 0xFFFFFFFE
};
static const BN_ULONG _nist_p_384[][BN_NIST_384_TOP] = {
        {
                0xFFFFFFFF, 0x00000000, 0x00000000, 0xFFFFFFFF,
                0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
        },
        {
                0xFFFFFFFE, 0x00000001, 0x00000000, 0xFFFFFFFE,
                0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
        },
        {
                0xFFFFFFFD, 0x00000002, 0x00000000, 0xFFFFFFFD,
                0xFFFFFFFC, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
        },
        {
                0xFFFFFFFC, 0x00000003, 0x00000000, 0xFFFFFFFC,
                0xFFFFFFFB, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
        },
        {
                0xFFFFFFFB, 0x00000004, 0x00000000, 0xFFFFFFFB,
                0xFFFFFFFA, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
                0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
        },
};
static const BN_ULONG _nist_p_384_sqr[] = {
        0x00000001, 0xFFFFFFFE, 0x00000000, 0x00000002, 0x00000000, 0xFFFFFFFE,
        0x00000000, 0x00000002, 0x00000001, 0x00000000, 0x00000000, 0x00000000,
        0xFFFFFFFE, 0x00000001, 0x00000000, 0xFFFFFFFE, 0xFFFFFFFD, 0xFFFFFFFF,
        0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF
};
static const BN_ULONG _nist_p_521[] = {
        0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
        0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
        0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
        0xFFFFFFFF, 0x000001FF
};
static const BN_ULONG _nist_p_521_sqr[] = {
        0x00000001, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000,
        0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000, 0x00000000,
        0x00000000, 0x00000000, 0x00000000, 0x00000000, 0xFFFFFC00, 0xFFFFFFFF,
        0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
        0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
        0xFFFFFFFF, 0xFFFFFFFF, 0x0003FFFF
};
#else
#error "unsupported BN_BITS2"
#endif

static const BIGNUM _bignum_nist_p_192 = {
        .d = (BN_ULONG *)_nist_p_192[0],
        .top = BN_NIST_192_TOP,
        .dmax = BN_NIST_192_TOP,
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_192_sqr = {
        .d = (BN_ULONG *)_nist_p_192_sqr,
        .top = sizeof(_nist_p_192_sqr) / sizeof(_nist_p_192_sqr[0]),
        .dmax = sizeof(_nist_p_192_sqr) / sizeof(_nist_p_192_sqr[0]),
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_224 = {
        .d = (BN_ULONG *)_nist_p_224[0],
        .top = BN_NIST_224_TOP,
        .dmax = BN_NIST_224_TOP,
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_224_sqr = {
        .d = (BN_ULONG *)_nist_p_224_sqr,
        .top = sizeof(_nist_p_224_sqr) / sizeof(_nist_p_224_sqr[0]),
        .dmax = sizeof(_nist_p_224_sqr) / sizeof(_nist_p_224_sqr[0]),
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_256 = {
        .d = (BN_ULONG *)_nist_p_256[0],
        .top = BN_NIST_256_TOP,
        .dmax = BN_NIST_256_TOP,
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_256_sqr = {
        .d = (BN_ULONG *)_nist_p_256_sqr,
        .top = sizeof(_nist_p_256_sqr) / sizeof(_nist_p_256_sqr[0]),
        .dmax = sizeof(_nist_p_256_sqr) / sizeof(_nist_p_256_sqr[0]),
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_384 = {
        .d = (BN_ULONG *)_nist_p_384[0],
        .top = BN_NIST_384_TOP,
        .dmax = BN_NIST_384_TOP,
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_384_sqr = {
        .d = (BN_ULONG *)_nist_p_384_sqr,
        .top = sizeof(_nist_p_384_sqr) / sizeof(_nist_p_384_sqr[0]),
        .dmax = sizeof(_nist_p_384_sqr) / sizeof(_nist_p_384_sqr[0]),
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_521 = {
        .d = (BN_ULONG *)_nist_p_521,
        .top = BN_NIST_521_TOP,
        .dmax = BN_NIST_521_TOP,
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

static const BIGNUM _bignum_nist_p_521_sqr = {
        .d = (BN_ULONG *)_nist_p_521_sqr,
        .top = sizeof(_nist_p_521_sqr) / sizeof(_nist_p_521_sqr[0]),
        .dmax = sizeof(_nist_p_521_sqr) / sizeof(_nist_p_521_sqr[0]),
        .neg = 0,
        .flags = BN_FLG_STATIC_DATA,
};

const BIGNUM *
BN_get0_nist_prime_192(void)
{
        return &_bignum_nist_p_192;
}

const BIGNUM *
BN_get0_nist_prime_224(void)
{
        return &_bignum_nist_p_224;
}

const BIGNUM *
BN_get0_nist_prime_256(void)
{
        return &_bignum_nist_p_256;
}

const BIGNUM *
BN_get0_nist_prime_384(void)
{
        return &_bignum_nist_p_384;
}

const BIGNUM *
BN_get0_nist_prime_521(void)
{
        return &_bignum_nist_p_521;
}

static void
nist_cp_bn_0(BN_ULONG *dst, const BN_ULONG *src, int top, int max)
{
        int i;

#ifdef BN_DEBUG
        OPENSSL_assert(top <= max);
#endif
        for (i = 0; i < top; i++)
                dst[i] = src[i];
        for (; i < max; i++)
                dst[i] = 0;
}

static void nist_cp_bn(BN_ULONG *dst, const BN_ULONG *src, int top)
{
        int i;

        for (i = 0; i < top; i++)
                dst[i] = src[i];
}

#if BN_BITS2 == 64
#define bn_cp_64(to, n, from, m)        (to)[n] = (m>=0)?((from)[m]):0;
#define bn_64_set_0(to, n)              (to)[n] = (BN_ULONG)0;
/*
 * two following macros are implemented under assumption that they
 * are called in a sequence with *ascending* n, i.e. as they are...
 */
#define bn_cp_32_naked(to, n, from, m)  (((n)&1)?(to[(n)/2]|=((m)&1)?(from[(m)/2]&BN_MASK2h):(from[(m)/2]<<32))\
                                                :(to[(n)/2] =((m)&1)?(from[(m)/2]>>32):(from[(m)/2]&BN_MASK2l)))
#define bn_32_set_0(to, n)              (((n)&1)?(to[(n)/2]&=BN_MASK2l):(to[(n)/2]=0));
#define bn_cp_32(to,n,from,m)           ((m)>=0)?bn_cp_32_naked(to,n,from,m):bn_32_set_0(to,n)
# if BYTE_ORDER == LITTLE_ENDIAN
#  if defined(_LP64)
#   define NIST_INT64 long
#  else
#   define NIST_INT64 long long
#  endif
# endif
#else
#define bn_cp_64(to, n, from, m) \
        { \
        bn_cp_32(to, (n)*2, from, (m)*2); \
        bn_cp_32(to, (n)*2+1, from, (m)*2+1); \
        }
#define bn_64_set_0(to, n) \
        { \
        bn_32_set_0(to, (n)*2); \
        bn_32_set_0(to, (n)*2+1); \
        }
#define bn_cp_32(to, n, from, m)        (to)[n] = (m>=0)?((from)[m]):0;
#define bn_32_set_0(to, n)              (to)[n] = (BN_ULONG)0;
# if defined(BN_LLONG)
#  define NIST_INT64 long long
# endif
#endif /* BN_BITS2 != 64 */

#define nist_set_192(to, from, a1, a2, a3) \
        { \
        bn_cp_64(to, 0, from, (a3) - 3) \
        bn_cp_64(to, 1, from, (a2) - 3) \
        bn_cp_64(to, 2, from, (a1) - 3) \
        }

int
BN_nist_mod_192(BIGNUM *r, const BIGNUM *a, const BIGNUM *field, BN_CTX *ctx)
{
        BN_ULONG bnbuf[BN_NIST_192_TOP] = { 0 };
        BN_ULONG c_d[BN_NIST_192_TOP] = { 0 };
        BN_ULONG *a_d = a->d;
        BN_ULONG *r_d, *res;
        uintptr_t mask;
        int top = a->top;
        int carry, i;

        field = &_bignum_nist_p_192; /* just to make sure */

        if (BN_is_negative(a) || BN_ucmp(a, &_bignum_nist_p_192_sqr) >= 0)
                return BN_nnmod(r, a, field, ctx);

        i = BN_ucmp(field, a);
        if (i == 0) {
                BN_zero(r);
                return 1;
        } else if (i > 0)
                return (r == a) ? 1 : (BN_copy(r , a) != NULL);

        if (r != a) {
                if (!bn_wexpand(r, BN_NIST_192_TOP))
                        return 0;
                r_d = r->d;
                nist_cp_bn(r_d, a_d, BN_NIST_192_TOP);
        } else
                r_d = a_d;

        nist_cp_bn_0(bnbuf, a_d + BN_NIST_192_TOP, top - BN_NIST_192_TOP,
            BN_NIST_192_TOP);

#if defined(NIST_INT64)
        {
                NIST_INT64 acc; /* accumulator */
                unsigned int bbuf[BN_NIST_192_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                unsigned int rbuf[BN_NIST_192_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                const unsigned int *bp = bbuf;
                unsigned int *rp = rbuf;

                CTASSERT(sizeof(bbuf) == sizeof(bnbuf));
                CTASSERT(sizeof(rbuf) == sizeof(bnbuf));

                /*
                 * Avoid strict aliasing violations by copying from an unsigned
                 * long array to an unsigned int array, then copying back the
                 * result. Any sensible compiler will omit the copies, while
                 * avoiding undefined behaviour that would result from unsafe
                 * type punning via pointer type casting.
                 */
                memcpy(bbuf, bnbuf, sizeof(bbuf));
                memcpy(rbuf, r_d, sizeof(rbuf));

                acc = rp[0];
                acc += bp[3 * 2 - 6];
                acc += bp[5 * 2 - 6];
                rp[0] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[1];
                acc += bp[3 * 2 - 5];
                acc += bp[5 * 2 - 5];
                rp[1] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[2];
                acc += bp[3 * 2 - 6];
                acc += bp[4 * 2 - 6];
                acc += bp[5 * 2 - 6];
                rp[2] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[3];
                acc += bp[3 * 2 - 5];
                acc += bp[4 * 2 - 5];
                acc += bp[5 * 2 - 5];
                rp[3] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[4];
                acc += bp[4 * 2 - 6];
                acc += bp[5 * 2 - 6];
                rp[4] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[5];
                acc += bp[4 * 2 - 5];
                acc += bp[5 * 2 - 5];
                rp[5] = (unsigned int)acc;

                memcpy(r_d, rbuf, sizeof(rbuf));

                carry = (int)(acc >> 32);
        }
#else
        {
                BN_ULONG t_d[BN_NIST_192_TOP] = {0};

                nist_set_192(t_d, bnbuf, 0, 3, 3);
                carry = (int)bn_add_words(r_d, r_d, t_d, BN_NIST_192_TOP);
                nist_set_192(t_d, bnbuf, 4, 4, 0);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_192_TOP);
                nist_set_192(t_d, bnbuf, 5, 5, 5)
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_192_TOP);
        }
#endif
        if (carry > 0)
                carry = (int)bn_sub_words(r_d, r_d, _nist_p_192[carry - 1],
                    BN_NIST_192_TOP);
        else
                carry = 1;

        /*
         * we need 'if (carry==0 || result>=modulus) result-=modulus;'
         * as comparison implies subtraction, we can write
         * 'tmp=result-modulus; if (!carry || !borrow) result=tmp;'
         * this is what happens below, but without explicit if:-) a.
         */
        mask = 0 - (uintptr_t)bn_sub_words(c_d, r_d, _nist_p_192[0],
            BN_NIST_192_TOP);
        mask &= 0 - (uintptr_t)carry;
        res = c_d;
        res = (BN_ULONG *)(((uintptr_t)res & ~mask) | ((uintptr_t)r_d & mask));
        nist_cp_bn(r_d, res, BN_NIST_192_TOP);
        r->top = BN_NIST_192_TOP;
        bn_correct_top(r);

        return 1;
}

typedef BN_ULONG (*bn_addsub_f)(BN_ULONG *, const BN_ULONG *,
    const BN_ULONG *, int);

#define nist_set_224(to, from, a1, a2, a3, a4, a5, a6, a7) \
        { \
        bn_cp_32(to, 0, from, (a7) - 7) \
        bn_cp_32(to, 1, from, (a6) - 7) \
        bn_cp_32(to, 2, from, (a5) - 7) \
        bn_cp_32(to, 3, from, (a4) - 7) \
        bn_cp_32(to, 4, from, (a3) - 7) \
        bn_cp_32(to, 5, from, (a2) - 7) \
        bn_cp_32(to, 6, from, (a1) - 7) \
        }

int
BN_nist_mod_224(BIGNUM *r, const BIGNUM *a, const BIGNUM *field, BN_CTX *ctx)
{
        BN_ULONG bnbuf[BN_NIST_224_TOP] = { 0 };
        BN_ULONG c_d[BN_NIST_224_TOP] = { 0 };
        BN_ULONG *a_d = a->d;
        BN_ULONG *r_d, *res;
        bn_addsub_f addsubf;
        uintptr_t mask;
        int top = a->top;
        int carry, i;

        field = &_bignum_nist_p_224; /* just to make sure */

        if (BN_is_negative(a) || BN_ucmp(a, &_bignum_nist_p_224_sqr) >= 0)
                return BN_nnmod(r, a, field, ctx);

        i = BN_ucmp(field, a);
        if (i == 0) {
                BN_zero(r);
                return 1;
        } else if (i > 0)
                return (r == a) ? 1 : (BN_copy(r, a) != NULL);

        if (r != a) {
                if (!bn_wexpand(r, BN_NIST_224_TOP))
                        return 0;
                r_d = r->d;
                nist_cp_bn(r_d, a_d, BN_NIST_224_TOP);
        } else
                r_d = a_d;

        memset(&bnbuf, 0, sizeof(bnbuf));

#if BN_BITS2==64
        /* copy upper 256 bits of 448 bit number ... */
        nist_cp_bn_0(c_d, a_d + (BN_NIST_224_TOP - 1),
            top - (BN_NIST_224_TOP - 1), BN_NIST_224_TOP);
        /* ... and right shift by 32 to obtain upper 224 bits */
        nist_set_224(bnbuf, c_d, 14, 13, 12, 11, 10, 9, 8);
        /* truncate lower part to 224 bits too */
        r_d[BN_NIST_224_TOP - 1] &= BN_MASK2l;
#else
        nist_cp_bn_0(bnbuf, a_d + BN_NIST_224_TOP,
            top - BN_NIST_224_TOP, BN_NIST_224_TOP);
#endif

#if defined(NIST_INT64) && BN_BITS2!=64
        {
                NIST_INT64 acc; /* accumulator */
                unsigned int bbuf[BN_NIST_224_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                unsigned int rbuf[BN_NIST_224_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                const unsigned int *bp = bbuf;
                unsigned int *rp = rbuf;

                CTASSERT(sizeof(bbuf) == sizeof(bnbuf));
                CTASSERT(sizeof(rbuf) == sizeof(bnbuf));

                /*
                 * Avoid strict aliasing violations by copying from an unsigned
                 * long array to an unsigned int array, then copying back the
                 * result. Any sensible compiler will omit the copies, while
                 * avoiding undefined behaviour that would result from unsafe
                 * type punning via pointer type casting.
                 */
                memcpy(bbuf, bnbuf, sizeof(bbuf));
                memcpy(rbuf, r_d, sizeof(rbuf));

                acc = rp[0];
                acc -= bp[7 - 7];
                acc -= bp[11 - 7];
                rp[0] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[1];
                acc -= bp[8 - 7];
                acc -= bp[12 - 7];
                rp[1] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[2];
                acc -= bp[9 - 7];
                acc -= bp[13 - 7];
                rp[2] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[3];
                acc += bp[7 - 7];
                acc += bp[11 - 7];
                acc -= bp[10 - 7];
                rp[3] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[4];
                acc += bp[8 - 7];
                acc += bp[12 - 7];
                acc -= bp[11 - 7];
                rp[4] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[5];
                acc += bp[9 - 7];
                acc += bp[13 - 7];
                acc -= bp[12 - 7];
                rp[5] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[6];
                acc += bp[10 - 7];
                acc -= bp[13 - 7];
                rp[6] = (unsigned int)acc;

                memcpy(r_d, rbuf, sizeof(rbuf));

                carry = (int)(acc >> 32);
# if BN_BITS2==64
                rp[7] = carry;
# endif
        }
#else
        {
                BN_ULONG t_d[BN_NIST_224_TOP] = {0};

                nist_set_224(t_d, bnbuf, 10, 9, 8, 7, 0, 0, 0);
                carry = (int)bn_add_words(r_d, r_d, t_d, BN_NIST_224_TOP);
                nist_set_224(t_d, bnbuf, 0, 13, 12, 11, 0, 0, 0);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_224_TOP);
                nist_set_224(t_d, bnbuf, 13, 12, 11, 10, 9, 8, 7);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_224_TOP);
                nist_set_224(t_d, bnbuf, 0, 0, 0, 0, 13, 12, 11);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_224_TOP);

#if BN_BITS2==64
                carry = (int)(r_d[BN_NIST_224_TOP - 1] >> 32);
#endif
        }
#endif
        addsubf = bn_sub_words;
        if (carry > 0) {
                carry = (int)bn_sub_words(r_d, r_d, _nist_p_224[carry - 1],
                    BN_NIST_224_TOP);
#if BN_BITS2==64
                carry = (int)(~(r_d[BN_NIST_224_TOP - 1] >> 32)) & 1;
#endif
        } else if (carry < 0) {
                /* it's a bit more complicated logic in this case.
                 * if bn_add_words yields no carry, then result
                 * has to be adjusted by unconditionally *adding*
                 * the modulus. but if it does, then result has
                 * to be compared to the modulus and conditionally
                 * adjusted by *subtracting* the latter. */
                carry = (int)bn_add_words(r_d, r_d, _nist_p_224[-carry - 1],
                    BN_NIST_224_TOP);
                if (carry == 0)
                        addsubf = bn_add_words;
        } else
                carry = 1;

        /* otherwise it's effectively same as in BN_nist_mod_192... */
        mask = 0 - (uintptr_t)(*addsubf)(c_d, r_d, _nist_p_224[0], BN_NIST_224_TOP);
        mask &= 0 - (uintptr_t)carry;
        res = c_d;
        res = (BN_ULONG *)(((uintptr_t)res & ~mask) | ((uintptr_t)r_d & mask));
        nist_cp_bn(r_d, res, BN_NIST_224_TOP);
        r->top = BN_NIST_224_TOP;
        bn_correct_top(r);

        return 1;
}

#define nist_set_256(to, from, a1, a2, a3, a4, a5, a6, a7, a8) \
        { \
        bn_cp_32(to, 0, from, (a8) - 8) \
        bn_cp_32(to, 1, from, (a7) - 8) \
        bn_cp_32(to, 2, from, (a6) - 8) \
        bn_cp_32(to, 3, from, (a5) - 8) \
        bn_cp_32(to, 4, from, (a4) - 8) \
        bn_cp_32(to, 5, from, (a3) - 8) \
        bn_cp_32(to, 6, from, (a2) - 8) \
        bn_cp_32(to, 7, from, (a1) - 8) \
        }

int
BN_nist_mod_256(BIGNUM *r, const BIGNUM *a, const BIGNUM *field, BN_CTX *ctx)
{
        BN_ULONG bnbuf[BN_NIST_256_TOP] = { 0 };
        BN_ULONG c_d[BN_NIST_256_TOP] = { 0 };
        BN_ULONG *a_d = a->d;
        BN_ULONG *r_d, *res;
        bn_addsub_f addsubf;
        uintptr_t mask;
        int top = a->top;
        int carry, i;

        field = &_bignum_nist_p_256; /* just to make sure */

        if (BN_is_negative(a) || BN_ucmp(a, &_bignum_nist_p_256_sqr) >= 0)
                return BN_nnmod(r, a, field, ctx);

        i = BN_ucmp(field, a);
        if (i == 0) {
                BN_zero(r);
                return 1;
        } else if (i > 0)
                return (r == a) ? 1 : (BN_copy(r, a) != NULL);

        if (r != a) {
                if (!bn_wexpand(r, BN_NIST_256_TOP))
                        return 0;
                r_d = r->d;
                nist_cp_bn(r_d, a_d, BN_NIST_256_TOP);
        } else
                r_d = a_d;

        nist_cp_bn_0(bnbuf, a_d + BN_NIST_256_TOP,
            top - BN_NIST_256_TOP, BN_NIST_256_TOP);

#if defined(NIST_INT64)
        {
                NIST_INT64 acc; /* accumulator */
                unsigned int bbuf[BN_NIST_256_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                unsigned int rbuf[BN_NIST_256_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                const unsigned int *bp = bbuf;
                unsigned int *rp = rbuf;

                CTASSERT(sizeof(bbuf) == sizeof(bnbuf));
                CTASSERT(sizeof(rbuf) == sizeof(bnbuf));

                /*
                 * Avoid strict aliasing violations by copying from an unsigned
                 * long array to an unsigned int array, then copying back the
                 * result. Any sensible compiler will omit the copies, while
                 * avoiding undefined behaviour that would result from unsafe
                 * type punning via pointer type casting.
                 */
                memcpy(bbuf, bnbuf, sizeof(bbuf));
                memcpy(rbuf, r_d, sizeof(rbuf));

                acc = rp[0];
                acc += bp[8 - 8];
                acc += bp[9 - 8];
                acc -= bp[11 - 8];
                acc -= bp[12 - 8];
                acc -= bp[13 - 8];
                acc -= bp[14 - 8];
                rp[0] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[1];
                acc += bp[9 - 8];
                acc += bp[10 - 8];
                acc -= bp[12 - 8];
                acc -= bp[13 - 8];
                acc -= bp[14 - 8];
                acc -= bp[15 - 8];
                rp[1] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[2];
                acc += bp[10 - 8];
                acc += bp[11 - 8];
                acc -= bp[13 - 8];
                acc -= bp[14 - 8];
                acc -= bp[15 - 8];
                rp[2] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[3];
                acc += bp[11 - 8];
                acc += bp[11 - 8];
                acc += bp[12 - 8];
                acc += bp[12 - 8];
                acc += bp[13 - 8];
                acc -= bp[15 - 8];
                acc -= bp[8 - 8];
                acc -= bp[9 - 8];
                rp[3] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[4];
                acc += bp[12 - 8];
                acc += bp[12 - 8];
                acc += bp[13 - 8];
                acc += bp[13 - 8];
                acc += bp[14 - 8];
                acc -= bp[9 - 8];
                acc -= bp[10 - 8];
                rp[4] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[5];
                acc += bp[13 - 8];
                acc += bp[13 - 8];
                acc += bp[14 - 8];
                acc += bp[14 - 8];
                acc += bp[15 - 8];
                acc -= bp[10 - 8];
                acc -= bp[11 - 8];
                rp[5] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[6];
                acc += bp[14 - 8];
                acc += bp[14 - 8];
                acc += bp[15 - 8];
                acc += bp[15 - 8];
                acc += bp[14 - 8];
                acc += bp[13 - 8];
                acc -= bp[8 - 8];
                acc -= bp[9 - 8];
                rp[6] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[7];
                acc += bp[15 - 8];
                acc += bp[15 - 8];
                acc += bp[15 - 8];
                acc += bp[8 - 8];
                acc -= bp[10 - 8];
                acc -= bp[11 - 8];
                acc -= bp[12 - 8];
                acc -= bp[13 - 8];
                rp[7] = (unsigned int)acc;

                memcpy(r_d, rbuf, sizeof(rbuf));

                carry = (int)(acc >> 32);
        }
#else
        {
                BN_ULONG t_d[BN_NIST_256_TOP] = {0};

                /*S1*/
                nist_set_256(t_d, bnbuf, 15, 14, 13, 12, 11, 0, 0, 0);
                /*S2*/
                nist_set_256(c_d, bnbuf, 0, 15, 14, 13, 12, 0, 0, 0);
                carry = (int)bn_add_words(t_d, t_d, c_d, BN_NIST_256_TOP);
                /* left shift */
                {
                        BN_ULONG *ap, t, c;
                        ap = t_d;
                        c = 0;
                        for (i = BN_NIST_256_TOP; i != 0; --i) {
                                t = *ap;
                                *(ap++) = ((t << 1) | c) & BN_MASK2;
                                c = (t & BN_TBIT) ? 1 : 0;
                        }
                        carry <<= 1;
                        carry |= c;
                }
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP);
                /*S3*/
                nist_set_256(t_d, bnbuf, 15, 14, 0, 0, 0, 10, 9, 8);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP);
                /*S4*/
                nist_set_256(t_d, bnbuf, 8, 13, 15, 14, 13, 11, 10, 9);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_256_TOP);
                /*D1*/
                nist_set_256(t_d, bnbuf, 10, 8, 0, 0, 0, 13, 12, 11);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);
                /*D2*/
                nist_set_256(t_d, bnbuf, 11, 9, 0, 0, 15, 14, 13, 12);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);
                /*D3*/
                nist_set_256(t_d, bnbuf, 12, 0, 10, 9, 8, 15, 14, 13);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);
                /*D4*/
                nist_set_256(t_d, bnbuf, 13, 0, 11, 10, 9, 0, 15, 14);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_256_TOP);

        }
#endif
        /* see BN_nist_mod_224 for explanation */
        addsubf = bn_sub_words;
        if (carry > 0)
                carry = (int)bn_sub_words(r_d, r_d, _nist_p_256[carry - 1],
                    BN_NIST_256_TOP);
        else if (carry < 0) {
                carry = (int)bn_add_words(r_d, r_d, _nist_p_256[-carry - 1],
                    BN_NIST_256_TOP);
                if (carry == 0)
                        addsubf = bn_add_words;
        } else
                carry = 1;

        mask = 0 - (uintptr_t)(*addsubf)(c_d, r_d, _nist_p_256[0], BN_NIST_256_TOP);
        mask &= 0 - (uintptr_t)carry;
        res = c_d;
        res = (BN_ULONG *)(((uintptr_t)res & ~mask) | ((uintptr_t)r_d & mask));
        nist_cp_bn(r_d, res, BN_NIST_256_TOP);
        r->top = BN_NIST_256_TOP;
        bn_correct_top(r);

        return 1;
}

#define nist_set_384(to,from,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10,a11,a12) \
        { \
        bn_cp_32(to, 0, from,  (a12) - 12) \
        bn_cp_32(to, 1, from,  (a11) - 12) \
        bn_cp_32(to, 2, from,  (a10) - 12) \
        bn_cp_32(to, 3, from,  (a9) - 12)  \
        bn_cp_32(to, 4, from,  (a8) - 12)  \
        bn_cp_32(to, 5, from,  (a7) - 12)  \
        bn_cp_32(to, 6, from,  (a6) - 12)  \
        bn_cp_32(to, 7, from,  (a5) - 12)  \
        bn_cp_32(to, 8, from,  (a4) - 12)  \
        bn_cp_32(to, 9, from,  (a3) - 12)  \
        bn_cp_32(to, 10, from, (a2) - 12)  \
        bn_cp_32(to, 11, from, (a1) - 12)  \
        }

int
BN_nist_mod_384(BIGNUM *r, const BIGNUM *a, const BIGNUM *field, BN_CTX *ctx)
{
        BN_ULONG bnbuf[BN_NIST_384_TOP] = { 0 };
        BN_ULONG c_d[BN_NIST_384_TOP] = { 0 };
        BN_ULONG *a_d = a->d;
        BN_ULONG *r_d, *res;
        bn_addsub_f addsubf;
        uintptr_t mask;
        int top = a->top;
        int carry, i;

        field = &_bignum_nist_p_384; /* just to make sure */

        if (BN_is_negative(a) || BN_ucmp(a, &_bignum_nist_p_384_sqr) >= 0)
                return BN_nnmod(r, a, field, ctx);

        i = BN_ucmp(field, a);
        if (i == 0) {
                BN_zero(r);
                return 1;
        } else if (i > 0)
                return (r == a) ? 1 : (BN_copy(r, a) != NULL);

        if (r != a) {
                if (!bn_wexpand(r, BN_NIST_384_TOP))
                        return 0;
                r_d = r->d;
                nist_cp_bn(r_d, a_d, BN_NIST_384_TOP);
        } else
                r_d = a_d;

        nist_cp_bn_0(bnbuf, a_d + BN_NIST_384_TOP,
            top - BN_NIST_384_TOP, BN_NIST_384_TOP);

#if defined(NIST_INT64)
        {
                NIST_INT64 acc; /* accumulator */
                unsigned int bbuf[BN_NIST_384_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                unsigned int rbuf[BN_NIST_384_TOP *
                    sizeof(BN_ULONG) / sizeof(unsigned int)];
                const unsigned int *bp = bbuf;
                unsigned int *rp = rbuf;

                CTASSERT(sizeof(bbuf) == sizeof(bnbuf));
                CTASSERT(sizeof(rbuf) == sizeof(bnbuf));

                /*
                 * Avoid strict aliasing violations by copying from an unsigned
                 * long array to an unsigned int array, then copying back the
                 * result. Any sensible compiler will omit the copies, while
                 * avoiding undefined behaviour that would result from unsafe
                 * type punning via pointer type casting.
                 */
                memcpy(bbuf, bnbuf, sizeof(bbuf));
                memcpy(rbuf, r_d, sizeof(rbuf));

                acc = rp[0];
                acc += bp[12 - 12];
                acc += bp[21 - 12];
                acc += bp[20 - 12];
                acc -= bp[23 - 12];
                rp[0] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[1];
                acc += bp[13 - 12];
                acc += bp[22 - 12];
                acc += bp[23 - 12];
                acc -= bp[12 - 12];
                acc -= bp[20 - 12];
                rp[1] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[2];
                acc += bp[14 - 12];
                acc += bp[23 - 12];
                acc -= bp[13 - 12];
                acc -= bp[21 - 12];
                rp[2] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[3];
                acc += bp[15 - 12];
                acc += bp[12 - 12];
                acc += bp[20 - 12];
                acc += bp[21 - 12];
                acc -= bp[14 - 12];
                acc -= bp[22 - 12];
                acc -= bp[23 - 12];
                rp[3] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[4];
                acc += bp[21 - 12];
                acc += bp[21 - 12];
                acc += bp[16 - 12];
                acc += bp[13 - 12];
                acc += bp[12 - 12];
                acc += bp[20 - 12];
                acc += bp[22 - 12];
                acc -= bp[15 - 12];
                acc -= bp[23 - 12];
                acc -= bp[23 - 12];
                rp[4] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[5];
                acc += bp[22 - 12];
                acc += bp[22 - 12];
                acc += bp[17 - 12];
                acc += bp[14 - 12];
                acc += bp[13 - 12];
                acc += bp[21 - 12];
                acc += bp[23 - 12];
                acc -= bp[16 - 12];
                rp[5] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[6];
                acc += bp[23 - 12];
                acc += bp[23 - 12];
                acc += bp[18 - 12];
                acc += bp[15 - 12];
                acc += bp[14 - 12];
                acc += bp[22 - 12];
                acc -= bp[17 - 12];
                rp[6] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[7];
                acc += bp[19 - 12];
                acc += bp[16 - 12];
                acc += bp[15 - 12];
                acc += bp[23 - 12];
                acc -= bp[18 - 12];
                rp[7] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[8];
                acc += bp[20 - 12];
                acc += bp[17 - 12];
                acc += bp[16 - 12];
                acc -= bp[19 - 12];
                rp[8] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[9];
                acc += bp[21 - 12];
                acc += bp[18 - 12];
                acc += bp[17 - 12];
                acc -= bp[20 - 12];
                rp[9] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[10];
                acc += bp[22 - 12];
                acc += bp[19 - 12];
                acc += bp[18 - 12];
                acc -= bp[21 - 12];
                rp[10] = (unsigned int)acc;
                acc >>= 32;

                acc += rp[11];
                acc += bp[23 - 12];
                acc += bp[20 - 12];
                acc += bp[19 - 12];
                acc -= bp[22 - 12];
                rp[11] = (unsigned int)acc;

                memcpy(r_d, rbuf, sizeof(rbuf));

                carry = (int)(acc >> 32);
        }
#else
        {
                BN_ULONG t_d[BN_NIST_384_TOP] = {0};

                /*S1*/
                nist_set_256(t_d, bnbuf, 0, 0, 0, 0, 0, 23 - 4, 22 - 4,
                    21 - 4);
                /* left shift */
                {
                        BN_ULONG *ap, t, c;
                        ap = t_d;
                        c = 0;
                        for (i = 3; i != 0; --i) {
                                t= *ap;
                                *(ap++) = ((t << 1)|c) & BN_MASK2;
                                c = (t & BN_TBIT) ? 1 : 0;
                        }
                        *ap = c;
                }
                carry = (int)bn_add_words(r_d + (128 / BN_BITS2),
                    r_d + (128 / BN_BITS2), t_d, BN_NIST_256_TOP);
                /*S2 */
                carry += (int)bn_add_words(r_d, r_d, bnbuf, BN_NIST_384_TOP);
                /*S3*/
                nist_set_384(t_d, bnbuf, 20, 19, 18, 17, 16, 15, 14, 13, 12,
                    23, 22, 21);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
                /*S4*/
                nist_set_384(t_d, bnbuf, 19, 18, 17, 16, 15, 14, 13, 12, 20,
                    0, 23, 0);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
                /*S5*/
                nist_set_384(t_d, bnbuf, 0,0, 0,0, 23, 22, 21, 20, 0,0, 0, 0);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
                /*S6*/
                nist_set_384(t_d, bnbuf, 0,0, 0,0, 0,0, 23, 22, 21, 0,0, 20);
                carry += (int)bn_add_words(r_d, r_d, t_d, BN_NIST_384_TOP);
                /*D1*/
                nist_set_384(t_d, bnbuf, 22, 21, 20, 19, 18, 17, 16, 15, 14,
                    13, 12, 23);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
                /*D2*/
                nist_set_384(t_d, bnbuf, 0,0, 0,0, 0,0, 0,23, 22, 21, 20, 0);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);
                /*D3*/
                nist_set_384(t_d, bnbuf, 0,0, 0,0, 0,0, 0,23, 23, 0,0, 0);
                carry -= (int)bn_sub_words(r_d, r_d, t_d, BN_NIST_384_TOP);

        }
#endif
        /* see BN_nist_mod_224 for explanation */
        addsubf = bn_sub_words;
        if (carry > 0)
                carry = (int)bn_sub_words(r_d, r_d, _nist_p_384[carry - 1],
                    BN_NIST_384_TOP);
        else if (carry < 0) {
                carry = (int)bn_add_words(r_d, r_d, _nist_p_384[-carry - 1],
                    BN_NIST_384_TOP);
                if (carry == 0)
                        addsubf = bn_add_words;
        } else
                carry = 1;

        mask = 0 - (uintptr_t)(*addsubf)(c_d, r_d, _nist_p_384[0], BN_NIST_384_TOP);
        mask &= 0 - (uintptr_t)carry;
        res = c_d;
        res = (BN_ULONG *)(((uintptr_t)res & ~mask) | ((uintptr_t)r_d & mask));
        nist_cp_bn(r_d, res, BN_NIST_384_TOP);
        r->top = BN_NIST_384_TOP;
        bn_correct_top(r);

        return 1;
}

#define BN_NIST_521_RSHIFT      (521%BN_BITS2)
#define BN_NIST_521_LSHIFT      (BN_BITS2-BN_NIST_521_RSHIFT)
#define BN_NIST_521_TOP_MASK    ((BN_ULONG)BN_MASK2>>BN_NIST_521_LSHIFT)

int
BN_nist_mod_521(BIGNUM *r, const BIGNUM *a, const BIGNUM *field, BN_CTX *ctx)
{
        BN_ULONG t_d[BN_NIST_521_TOP] = { 0 };
        BN_ULONG *a_d = a->d;
        BN_ULONG *r_d, *res;
        BN_ULONG tmp, val;
        uintptr_t mask;
        int top = a->top;
        int i;

        field = &_bignum_nist_p_521; /* just to make sure */

        if (BN_is_negative(a) || BN_ucmp(a, &_bignum_nist_p_521_sqr) >= 0)
                return BN_nnmod(r, a, field, ctx);

        i = BN_ucmp(field, a);
        if (i == 0) {
                BN_zero(r);
                return 1;
        } else if (i > 0)
                return (r == a) ? 1 : (BN_copy(r, a) != NULL);

        if (r != a) {
                if (!bn_wexpand(r, BN_NIST_521_TOP))
                        return 0;
                r_d = r->d;
                nist_cp_bn(r_d, a_d, BN_NIST_521_TOP);
        } else
                r_d = a_d;

        /* upper 521 bits, copy ... */
        nist_cp_bn_0(t_d, a_d + (BN_NIST_521_TOP - 1),
            top - (BN_NIST_521_TOP - 1), BN_NIST_521_TOP);
        /* ... and right shift */
        for (val = t_d[0], i = 0; i < BN_NIST_521_TOP - 1; i++) {
                tmp = val >> BN_NIST_521_RSHIFT;
                val = t_d[i + 1];
                t_d[i] = (tmp | val << BN_NIST_521_LSHIFT) & BN_MASK2;
        }
        t_d[i] = val >> BN_NIST_521_RSHIFT;
        /* lower 521 bits */
        r_d[i] &= BN_NIST_521_TOP_MASK;

        bn_add_words(r_d, r_d, t_d, BN_NIST_521_TOP);
        mask = 0 - (uintptr_t)bn_sub_words(t_d, r_d, _nist_p_521,
            BN_NIST_521_TOP);
        res = t_d;
        res = (BN_ULONG *)(((uintptr_t)res & ~mask) | ((uintptr_t)r_d & mask));
        nist_cp_bn(r_d, res, BN_NIST_521_TOP);
        r->top = BN_NIST_521_TOP;
        bn_correct_top(r);

        return 1;
}