if (!(m->d[0] & 1))
if (m->top == 0 || !(m->d[0] & 1))
int BN_mod_exp_mont_word(BIGNUM *rr, BN_ULONG a, const BIGNUM *p,                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)	{	BN_MONT_CTX *mont = NULL;	int b, bits, ret=0;	int r_is_one;	BN_ULONG w, next_w;	BIGNUM *d, *r, *t;	BIGNUM *swap_tmp;#define BN_MOD_MUL_WORD(r, w, m) \		(BN_mul_word(r, (w)) && \		(/* BN_ucmp(r, (m)) < 0 ? 1 :*/  \			(BN_mod(t, r, m, ctx) && (swap_tmp = r, r = t, t = swap_tmp, 1))))		/* BN_MOD_MUL_WORD is only used with 'w' large,		  * so the BN_ucmp test is probably more overhead		  * than always using BN_mod (which uses BN_copy if		  * a similar test returns true). */#define BN_TO_MONTGOMERY_WORD(r, w, mont) \		(BN_set_word(r, (w)) && BN_to_montgomery(r, r, (mont), ctx))	bn_check_top(p);	bn_check_top(m);	if (!(m->d[0] & 1))		{		BNerr(BN_F_BN_MOD_EXP_MONT_WORD,BN_R_CALLED_WITH_EVEN_MODULUS);		return(0);		}	bits = BN_num_bits(p);	if (bits == 0)		{		ret = BN_one(rr);		return ret;		}	if (a == 0)		{		ret = BN_zero(rr);		return ret;		}	BN_CTX_start(ctx);	d = BN_CTX_get(ctx);	r = BN_CTX_get(ctx);	t = BN_CTX_get(ctx);	if (d == NULL || r == NULL || t == NULL) goto err;	if (in_mont != NULL)		mont=in_mont;	else		{		if ((mont = BN_MONT_CTX_new()) == NULL) goto err;		if (!BN_MONT_CTX_set(mont, m, ctx)) goto err;		}	r_is_one = 1; /* except for Montgomery factor */	/* bits-1 >= 0 */	/* The result is accumulated in the product r*w. */	w = a; /* bit 'bits-1' of 'p' is always set */	for (b = bits-2; b >= 0; b--)		{		/* First, square r*w. */		next_w = w*w;		if ((next_w/w) != w) /* overflow */			{			if (r_is_one)				{				if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;				r_is_one = 0;				}			else				{				if (!BN_MOD_MUL_WORD(r, w, m)) goto err;				}			next_w = 1;			}		w = next_w;		if (!r_is_one)			{			if (!BN_mod_mul_montgomery(r, r, r, mont, ctx)) goto err;			}		/* Second, multiply r*w by 'a' if exponent bit is set. */		if (BN_is_bit_set(p, b))			{			next_w = w*a;			if ((next_w/a) != w) /* overflow */				{				if (r_is_one)					{					if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;					r_is_one = 0;					}				else					{					if (!BN_MOD_MUL_WORD(r, w, m)) goto err;					}				next_w = a;				}			w = next_w;			}		}	/* Finally, set r:=r*w. */	if (w != 1)		{		if (r_is_one)			{			if (!BN_TO_MONTGOMERY_WORD(r, w, mont)) goto err;			r_is_one = 0;			}		else			{			if (!BN_MOD_MUL_WORD(r, w, m)) goto err;			}		}	if (r_is_one) /* can happen only if a == 1*/		{		if (!BN_one(rr)) goto err;		}	else		{		if (!BN_from_montgomery(rr, r, mont, ctx)) goto err;		}	ret = 1;err:	if ((in_mont == NULL) && (mont != NULL)) BN_MONT_CTX_free(mont);	BN_CTX_end(ctx);	return(ret);	}