if (!a->neg && BN_ucmp(a,m) >= 0)
if (a->neg || BN_ucmp(a,m) >= 0)
int BN_mod_exp_mont(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,		    const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *in_mont)	{	int i,j,bits,ret=0,wstart,wend,window,wvalue;	int start=1,ts=0;	BIGNUM *d,*r;	const BIGNUM *aa;	BIGNUM val[TABLE_SIZE];	BN_MONT_CTX *mont=NULL;	bn_check_top(a);	bn_check_top(p);	bn_check_top(m);	if (!(m->d[0] & 1))		{		BNerr(BN_F_BN_MOD_EXP_MONT,BN_R_CALLED_WITH_EVEN_MODULUS);		return(0);		}	bits=BN_num_bits(p);	if (bits == 0)		{		BN_one(rr);		return(1);		}	BN_CTX_start(ctx);	d = BN_CTX_get(ctx);	r = BN_CTX_get(ctx);	if (d == NULL || r == NULL) goto err;	/* If this is not done, things will break in the montgomery	 * part */	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;		}	BN_init(&val[0]);	ts=1;	if (!a->neg && BN_ucmp(a,m) >= 0)		{		if (!BN_nnmod(&(val[0]),a,m,ctx))			goto err;		aa= &(val[0]);		}	else		aa=a;	if (!BN_to_montgomery(&(val[0]),aa,mont,ctx)) goto err; /* 1 */	window = BN_window_bits_for_exponent_size(bits);	if (window > 1)		{		if (!BN_mod_mul_montgomery(d,&(val[0]),&(val[0]),mont,ctx)) goto err; /* 2 */		j=1<<(window-1);		for (i=1; i<j; i++)			{			BN_init(&(val[i]));			if (!BN_mod_mul_montgomery(&(val[i]),&(val[i-1]),d,mont,ctx))				goto err;			}		ts=i;		}	start=1;	/* This is used to avoid multiplication etc			 * when there is only the value '1' in the			 * buffer. */	wvalue=0;	/* The 'value' of the window */	wstart=bits-1;	/* The top bit of the window */	wend=0;		/* The bottom bit of the window */	if (!BN_to_montgomery(r,BN_value_one(),mont,ctx)) goto err;	for (;;)		{		if (BN_is_bit_set(p,wstart) == 0)			{			if (!start)				{				if (!BN_mod_mul_montgomery(r,r,r,mont,ctx))				goto err;				}			if (wstart == 0) break;			wstart--;			continue;			}		/* We now have wstart on a 'set' bit, we now need to work out		 * how bit a window to do.  To do this we need to scan		 * forward until the last set bit before the end of the		 * window */		j=wstart;		wvalue=1;		wend=0;		for (i=1; i<window; i++)			{			if (wstart-i < 0) break;			if (BN_is_bit_set(p,wstart-i))				{				wvalue<<=(i-wend);				wvalue|=1;				wend=i;				}			}		/* wend is the size of the current window */		j=wend+1;		/* add the 'bytes above' */		if (!start)			for (i=0; i<j; i++)				{				if (!BN_mod_mul_montgomery(r,r,r,mont,ctx))					goto err;				}				/* wvalue will be an odd number < 2^window */		if (!BN_mod_mul_montgomery(r,r,&(val[wvalue>>1]),mont,ctx))			goto err;		/* move the 'window' down further */		wstart-=wend+1;		wvalue=0;		start=0;		if (wstart < 0) break;		}	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);	for (i=0; i<ts; i++)		BN_clear_free(&(val[i]));	return(ret);	}