int BN_mod_mul_montgomery(BIGNUM *r, BIGNUM *a, BIGNUM *b,
			  BN_MONT_CTX *mont, BN_CTX *ctx)
	{
	BIGNUM *tmp,*tmp2;
	int ret=0;

	BN_CTX_start(ctx);
	tmp = BN_CTX_get(ctx);
	tmp2 = BN_CTX_get(ctx);
	if (tmp == NULL || tmp2 == NULL) goto err;

	bn_check_top(tmp);
	bn_check_top(tmp2);

	if (a == b)
		{
#if 0 /* buggy -- try squaring  g  in the following parameters
         (but note that squaring 2 or 4 works):
Diffie-Hellman-Parameters: (1024 bit)
    prime:
        00:ff:ff:ff:ff:ff:ff:ff:ff:c9:0f:da:a2:21:68:
        c2:34:c4:c6:62:8b:80:dc:1c:d1:29:02:4e:08:8a:
        67:cc:74:02:0b:be:a6:3b:13:9b:22:51:4a:08:79:
        8e:34:04:dd:ef:95:19:b3:cd:3a:43:1b:30:2b:0a:
        6d:f2:5f:14:37:4f:e1:35:6d:6d:51:c2:45:e4:85:
        b5:76:62:5e:7e:c6:f4:4c:42:e9:a6:37:ed:6b:0b:
        ff:5c:b6:f4:06:b7:ed:ee:38:6b:fb:5a:89:9f:a5:
        ae:9f:24:11:7c:4b:1f:e6:49:28:66:51:ec:e6:53:
        81:ff:ff:ff:ff:ff:ff:ff:ff
    generator: 8 (0x8)
-----BEGIN DH PARAMETERS-----
MIGHAoGBAP//////////yQ/aoiFowjTExmKLgNwc0SkCTgiKZ8x0Agu+pjsTmyJR
Sgh5jjQE3e+VGbPNOkMbMCsKbfJfFDdP4TVtbVHCReSFtXZiXn7G9ExC6aY37WsL
/1y29Aa37e44a/taiZ+lrp8kEXxLH+ZJKGZR7OZTgf//////////AgEI
-----END DH PARAMETERS-----
*/
		bn_wexpand(tmp,a->top*2);
		bn_wexpand(tmp2,a->top*4);
		bn_sqr_recursive(tmp->d,a->d,a->top,tmp2->d);
		tmp->top=a->top*2;
		if (tmp->top > 0 && tmp->d[tmp->top-1] == 0)
			tmp->top--;
#else
		if (!BN_sqr(tmp,a,ctx)) goto err;
#endif
		}
	else
		{
		if (!BN_mul(tmp,a,b,ctx)) goto err;
		}
	/* reduce from aRR to aR */
	if (!BN_from_montgomery(r,tmp,mont,ctx)) goto err;
	ret=1;
err:
	BN_CTX_end(ctx);
	return(ret);
	}