Change submitted files so that they compile (in particular,

use BN_CTX_start/get/end instead of accessing ctx->tos).

Change indentation to "EAY" style.

crypto/bn/bn_modfs.c

@@ -20,70 +20,69 @@
 
 
 int BN_legendre(BIGNUM *a, BIGNUM *p, BN_CTX *ctx) 
-{
+	{
 	BIGNUM *x, *y, *y2;
 	BN_ULONG m;
 	int L;
 
 	assert(a != NULL && p != NULL && ctx != NULL);
 
-	x = ctx->bn[ctx->tos]; 
-	y = ctx->bn[ctx->tos + 1]; 
-	y2 = ctx->bn[ctx->tos + 2]; 
-
-	ctx->tos += 3;
+	BN_CTX_start(ctx);
+	x = BN_CTX_get(ctx);
+	y = BN_CTX_get(ctx);
+	y2 = BN_CTX_get(ctx);
+	if (y2 == NULL) goto err;
 
 	if (!BN_nnmod(x, a, p, ctx)) goto err;
 	if (BN_is_zero(x)) 
-	{
-
-		ctx->tos -= 3;
+		{
+		BN_CTX_end(ctx);
 		return 0;
-	}
+		}
 
 	if (BN_copy(y, p) == NULL) goto err;
 	L = 1;
 
 	while (1)
-	{
+		{
 		if (!BN_rshift1(y2, y)) goto err;
 		if (BN_cmp(x, y2) > 0)
-		{
+			{
 			if (!BN_sub(x, y, x)) goto err;
 			if (BN_mod_word(y, 4) == 3)
 				L = -L;			
-		}
+			}
 		while (BN_mod_word(x, 4) == 0)
 			BN_div_word(x, 4);
 		if (BN_mod_word(x, 2) == 0)
-		{
+			{
 			BN_div_word(x, 2);
 			m = BN_mod_word(y, 8);
 			if (m == 3 || m == 5) L = -L;			
-		}
+			}
 		if (BN_is_one(x)) 
-		{
-			ctx->tos -= 3;
+			{
+			BN_CTX_end(ctx);
 			return L;
-		}
+			}
 		
 		if (BN_mod_word(x, 4) == 3 && BN_mod_word(y, 4) == 3) L = -L;
-		if (!BN_swap(x, y)) goto err;
+		BN_swap(x, y);
 
 		if (!BN_nnmod(x, x, y, ctx)) goto err;
 
-	}
+		}
 
 
 err:
-	ctx->tos -= 3;
+	BN_CTX_end(ctx);
 	return -2;
 
-}
+	}
 
 int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx) 
 /* x^2 = a (mod p) */
-{
+	{
 	int ret;
 	BIGNUM *n0, *n1, *r, *b, *m;
 	int max;
@@ -94,14 +93,15 @@ int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
 	ret = BN_legendre(a, p, ctx);
 	if (ret < 0 || ret > 1) return 0;
 	if (ret == 0)
-	{
+		{
 		if (!BN_zero(x)) return 0;
 		return 1;
-	}
+		}
 
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	ctx->tos += 2;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	if (n1 == NULL) goto err;
 
 	if ((r = BN_new()) == NULL) goto err;
 	if ((b = BN_new()) == NULL) goto err;
@@ -116,22 +116,23 @@ int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
 
 	max = 0;
 
-	do{
+	do
+		{
 		if (max++ > MAX_ROUNDS) goto err; /* if p is not prime could never stop*/
 		if (!BN_add_word(m, 1)) goto err;
 		ret = BN_legendre(m, p, ctx);
 		if (ret < -1 || ret > 1) goto err;
-
-	}while(ret != -1);
+		}
+	while (ret != -1);
 
 	if (BN_copy(n1, p) == NULL) goto err;
 	if (!BN_sub_word(n1, 1)) goto err;
 
 	while (!BN_is_odd(n1))
-	{
+		{
 		if (!BN_add_word(r, 1)) goto err;
 		if (!BN_rshift1(n1, n1)) goto err;
-	}
+		}
 
 	if (!BN_mod_exp_simple(n0, m, n1, p, ctx)) goto err;
 
@@ -145,15 +146,14 @@ int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
 	if (!BN_mod_mul(x, x, a, p, ctx)) goto err;
 
 	while (!BN_is_one(b))
-	{
-		
+		{
 		if (!BN_one(m)) goto err;
 		if (!BN_mod_sqr(n1, b, p, ctx)) goto err;
 		while(!BN_is_one(n1))
-		{
+			{
 			if (!BN_mod_mul(n1, n1, n1, p, ctx)) goto err;
 			if (!BN_add_word(m, 1)) goto err;
-		}
+			}
 
 		if (!BN_sub(r, r, m)) goto err;
 		if (!BN_sub_word(r, 1)) goto err;
@@ -161,16 +161,16 @@ int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
 
 		if (BN_copy(n1, n0) == NULL) goto err;
 		while(!BN_is_zero(r))
-		{
+			{
 			if (!BN_mod_mul(n1, n1, n1, p, ctx)) goto err;
 			if (!BN_sub_word(r, 1)) goto err;
-		}
+			}
 
 		if (!BN_mod_mul(n0, n1, n1, p, ctx)) goto err;
 		if (BN_copy(r, m) == NULL) goto err;
 		if (!BN_mod_mul(x, x, n1, p, ctx)) goto err;
 		if (!BN_mod_mul(b, b, n0, p, ctx)) goto err;
-	}
+		}
 
 
 #ifdef TEST
@@ -181,12 +181,12 @@ int BN_mod_sqrt(BIGNUM *x, BIGNUM *a, BIGNUM *p, BN_CTX *ctx)
 	if (r != NULL) BN_clear_free(r);
 	if (b != NULL) BN_clear_free(b);
 	if (m != NULL) BN_clear_free(m);
-	ctx->tos -= 2;
+	BN_CTX_end(ctx);
 	return 1;
 err:
 	if (r != NULL) BN_clear_free(r);
 	if (b != NULL) BN_clear_free(b);
 	if (m != NULL) BN_clear_free(m);
-	ctx->tos -= 2;
+	BN_CTX_end(ctx);
 	return 0;
-}
+	}

crypto/ec/ec.h

@@ -15,7 +15,7 @@
 
 
 #include <openssl/bn.h>
-#include "bn_mont2.h"
+#include "../bn/bn_mont2.h" /* XXX */
 
 typedef struct bn_ec_struct		/* E: y^2 = x^3 + Ax + B  (mod p) */
 {

crypto/ec/ec_point.c

@@ -16,12 +16,13 @@
 
 #include <openssl/bn.h>
 
-#include "bn_modfs.h"
-#include "bn_mont2.h"
+#include "../bn/bn_modfs.h" /* XXX */
+#include "../bn/bn_mont2.h" /* XXX */
 #include "ec.h"
 
+
 EC_POINT *ECP_new()
-{
+	{
 	EC_POINT *ret;
 
 	ret=(EC_POINT *)malloc(sizeof(EC_POINT));
@@ -31,19 +32,20 @@ EC_POINT *ECP_new()
 	ret->Z = BN_new();
 	ret->is_in_mont = 0;
 
-	if (ret->X == NULL || ret->Y == NULL || ret->Z == NULL) 
-	{
+	if (ret->X == NULL || ret->Y == NULL || ret->Z == NULL)
+		{
 		if (ret->X != NULL) BN_free(ret->X);
 		if (ret->Y != NULL) BN_free(ret->Y);
 		if (ret->Z != NULL) BN_free(ret->Z);
 		free(ret);
 		return(NULL);
-	}
+		}
 	return(ret);
-}
+	}
+
 
 void ECP_clear_free(EC_POINT *P)
-{
+	{
 	if (P == NULL) return;
 	
 	P->is_in_mont = 0;
@@ -51,31 +53,34 @@ void ECP_clear_free(EC_POINT *P)
 	if (P->Y != NULL) BN_clear_free(P->Y);
 	if (P->Z != NULL) BN_clear_free(P->Z);
 	free(P);
-}
+	}
+
 
 void ECP_clear_free_precompute(ECP_PRECOMPUTE *prec)
-{
+	{
 	int i;
 	int max;
 
 	if (prec == NULL) return;
 	if (prec->Pi != NULL)
-	{
+		{
 		max = 1;
 		max <<= (prec->r - 1);
 
 		for (i = 0; i < max; i++)
-		{
+			{
 			if (prec->Pi[i] != NULL) ECP_clear_free(prec->Pi[i]);
+			}
 		}
-	}
 	free(prec);
-}
+	}
+
 
 int ECP_is_on_ec(EC_POINT *P, EC *E, BN_CTX *ctx)
-{
+	{
 	BIGNUM *n0, *n1, *n2, *p;
 	int Pnorm;
+	int ret = -1;
 
 	assert(P != NULL);
 	assert(P->X != NULL && P->Y != NULL && P->Z != NULL);
@@ -89,70 +94,67 @@ int ECP_is_on_ec(EC_POINT *P, EC *E, BN_CTX *ctx)
 
 	if (ECP_is_infty(P)) return 1;
 	
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	n2 = ctx->bn[ctx->tos + 2]; 
-	ctx->tos += 3;
-
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	n2 = BN_CTX_get(ctx);
+	if (n2 == NULL)
+		goto err;
 
 	p = E->p;
 
 	Pnorm = (ECP_is_norm(P));
 
 	if (!Pnorm)
-	{
+		{
 		if (!BN_mod_mul(n0, P->Z, P->Z, p, ctx)) goto err;
 		if (!BN_mod_mul(n1, n0, n0, p, ctx)) goto err;
 		if (!BN_mod_mul(n2, n0, n1, p, ctx)) goto err;
-	}
+		}
 
 	if (!BN_mod_mul(n0, P->X, P->X, p, ctx)) goto err;
 	if (!BN_mod_mul(n0, n0, P->X, p, ctx)) goto err;
 
 	if (Pnorm)
-	{
+		{
 		if (!BN_mod_mul(n1, P->X, E->A, p, ctx)) goto err;
-	}
+		}
 	else
-	{
+		{
 		if (!BN_mod_mul(n1, n1, P->X, p, ctx)) goto err;
 		if (!BN_mod_mul(n1, n1, E->A, p, ctx)) goto err;
-	}
+		}
 	if (!BN_mod_add(n0, n0, n1, p, ctx)) goto err;
 
 	if (Pnorm)
-	{
+		{
 		if (!BN_mod_add(n0, n0, E->B, p, ctx)) goto err;
-	}
+		}
 	else
-	{
+		{
 		if (!BN_mod_mul(n2, n2, E->B,  p, ctx)) goto err;
 		if (!BN_mod_add(n0, n0, n2, p, ctx)) goto err;
-	}
-
+		}
+	
 	if (!BN_mod_mul(n1, P->Y, P->Y, p, ctx)) goto err;
 
-	if (BN_cmp(n0, n1)) 
-	{ 
-		ctx->tos -= 3;
-		return 0;
-	}
+	if (BN_cmp(n0, n1))
+		ret = 0;
+	else
+		ret = 1;
 
-	ctx->tos -= 3;
-	return 1;
-	
 err:
-	ctx->tos -= 3;
-	return -1;
-}
+	BN_CTX_end(ctx);
+	return ret;
+	}
 
 
 EC_POINT *ECP_generate(BIGNUM *x, BIGNUM *z,EC *E, BN_CTX *ctx)
 /* x == NULL || z = 0  -> point of infinity	*/
 /* z == NULL || z = 1  -> normalized		*/
-{
+	{
 	BIGNUM *n0, *n1;
-	EC_POINT *ret;
+	EC_POINT *ret = NULL;
 	int Pnorm, Pinfty, X0, A0;
 
 	assert(E != NULL);
@@ -162,22 +164,22 @@ EC_POINT *ECP_generate(BIGNUM *x, BIGNUM *z,EC *E, BN_CTX *ctx)
 
 	Pinfty = (x == NULL);
 	Pnorm = (z == NULL);
-	if (!Pnorm) 
-	{
+	if (!Pnorm)
+		{
 		Pnorm = BN_is_one(z);
 		Pinfty = (Pinfty || BN_is_zero(z));
-	}
+		}
 
-	if (Pinfty) 
-	{
+	if (Pinfty)
+		{
 		if ((ret = ECP_new()) == NULL) return NULL;
-		if (!BN_zero(ret->Z)) 
-		{ 
+		if (!BN_zero(ret->Z))
+			{
 			ECP_clear_free(ret);
 			return NULL;
-		}
+			}
 		return ret;
-	}
+		}
 
 	X0 = BN_is_zero(x);
 	A0 = BN_is_zero(E->A);
@@ -186,24 +188,25 @@ EC_POINT *ECP_generate(BIGNUM *x, BIGNUM *z,EC *E, BN_CTX *ctx)
 
 	ret->is_in_mont = 0;
 
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	if (!BN_zero(n0)) return NULL;
-	if (!BN_zero(n1)) return NULL;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	if (n1 == NULL) goto err;
 
-	ctx->tos += 2;
+	if (!BN_zero(n0)) goto err;
+	if (!BN_zero(n1)) goto err;
 
 	if (!X0)
-	{
+		{
 		if (!BN_mod_sqr(n0, x, E->p, ctx)) goto err;
 		if (!BN_mod_mul(n0, n0, x, E->p, ctx)) goto err;	/* x^3 */
-	}
+		}
 
 	if (!X0 && !A0)
-	{
+		{
 		if (!BN_mod_mul(n1, E->A, x, E->p, ctx)) goto err;	/* Ax */
 		if (!BN_mod_add(n0, n0, n1, E->p, ctx)) goto err;	/* x^3 + Ax */
-	}
+		}
 
 	if (!BN_is_zero(E->B))
 		if (!BN_mod_add(n0, n0, E->B, E->p, ctx)) goto err;	/* x^3 + Ax +B */
@@ -212,36 +215,37 @@ EC_POINT *ECP_generate(BIGNUM *x, BIGNUM *z,EC *E, BN_CTX *ctx)
 	if (BN_copy(ret->X, x) == NULL) goto err;
 	
 	if (Pnorm)
-	{
+		{
 		if (!BN_one(ret->Z)) goto err;
-	}
+		}
 	else
-	{
+		{
 		if (BN_copy(ret->Z, z) == NULL) goto err;
 		if (!BN_mod_sqr(n0, z, E->p, ctx)) goto err;
 		if (!BN_mod_mul(ret->X, ret->X, n0, E->p, ctx)) goto err;
 		if (!BN_mod_mul(n0, n0, z, E->p, ctx)) goto err;
 		if (!BN_mod_mul(ret->Y, ret->Y, n0, E->p, ctx)) goto err;
-	}
+		}
 
 #ifdef TEST
 	if (!ECP_is_on_ec(ret, E, ctx)) goto err;
 #endif
 	
-	ctx->tos -= 2;
+	BN_CTX_end(ctx);
 	return ret;
 
 err:
 	if (ret != NULL) ECP_clear_free(ret);
-	ctx->tos -= 2;
+	BN_CTX_end(ctx);
 	return NULL;
-}
+	}
+
 
 int ECP_ecp2bin(EC_POINT *P, unsigned char *to, int form)
 /* form =	1 ... compressed
-			2 ... uncompressed
-			3 ... hybrid */
-{
+                2 ... uncompressed
+                3 ... hybrid */
+	{
 	int bytes, bx, by;
 
 	assert (P != NULL);
@@ -252,41 +256,42 @@ int ECP_ecp2bin(EC_POINT *P, unsigned char *to, int form)
 	assert (form > 0 && form < 4);
 
 	if (BN_is_zero(P->Z))
-	{
+		{
 		to[0] = 0;
 		return 1;
-	}
+		}
 
 	bx = BN_num_bytes(P->X);
 	if (form == 1 ) bytes = bx + 1;
-	else 
-	{
+	else
+		{
 		by = BN_num_bytes(P->Y);
 		bytes = (bx > by ? bx : by);
 		bytes = bytes * 2 + 1;
-	}
+		}
 	memset(to, 0, bytes);
 
 	switch (form)
-	{
+		{
 	case 1: to[0] = 2;	break;
 	case 2: to[0] = 4;	break;
 	case 3: to[0] = 6;	break;
-	}
+		}
 	if (form != 2) to[0] += BN_is_bit_set(P->Y, 0);
 
 	
 	if ((BN_bn2bin(P->X, to + 1)) != bx) return 0;
 	if (form != 1)
-	{
+		{
 		if ((BN_bn2bin(P->Y, to + bx + 1)) != by) return 0;
-	}
+		}
 
 	return bytes;
-}
+	}
+
 
 int ECP_bin2ecp(unsigned char *from, int len, EC_POINT *P, EC *E, BN_CTX *ctx)
-{
+	{
 	int y;
 	BIGNUM *x;
 	EC_POINT *pp;
@@ -303,13 +308,13 @@ int ECP_bin2ecp(unsigned char *from, int len, EC_POINT *P, EC *E, BN_CTX *ctx)
 	if (len == 1 && from[0] != 0) return 0;
 
 	if (len == 0 || len == 1)
-	{ 
+		{
 		if (!BN_zero(P->Z)) return 0;
 		return 1;
-	}
+		}
 
 	switch (from[0])
-	{
+		{
 	case 2:
 	case 3:
 		y = from[0] - 2;
@@ -339,14 +344,15 @@ int ECP_bin2ecp(unsigned char *from, int len, EC_POINT *P, EC *E, BN_CTX *ctx)
 	default:
 		assert(0);
 
-	}
+		}
 
 	if (!ECP_is_on_ec(P, E, ctx)) return 0;
 	return 1;
-}
+	}
+
 
 int ECP_normalize(EC_POINT *P, EC *E, BN_CTX *ctx)
-{
+	{
 	BIGNUM *z, *zm;
 
 	assert (P != NULL);
@@ -365,8 +371,9 @@ int ECP_normalize(EC_POINT *P, EC *E, BN_CTX *ctx)
 	assert(!P->is_in_mont);
 
 
-	z = ctx->bn[ctx->tos]; 
-	ctx->tos++;
+	BN_CTX_start(ctx);
+	z = BN_CTX_get(ctx);
+	if (z == NULL) goto err;
 
 	if (!BN_mod_mul(z, zm, zm, E->p, ctx)) goto err;
 	if (!BN_mod_mul(P->X, P->X, z, E->p, ctx)) goto err;
@@ -378,17 +385,18 @@ int ECP_normalize(EC_POINT *P, EC *E, BN_CTX *ctx)
 
 	if (zm != NULL) BN_clear_free(zm);
 
-	ctx->tos--;
+	BN_CTX_end(ctx);
 	return 1;
 
 err:
 	if (zm != NULL) BN_clear_free(zm);
-	ctx->tos--;
+	BN_CTX_end(ctx);
 	return 0;
-}
+	}
+
 
 int ECP_copy(EC_POINT *R, EC_POINT *P)
-{
+	{
 	assert(P != NULL);
 	assert(P->X != NULL && P->Y != NULL && P->Z != NULL);
 
@@ -401,27 +409,28 @@ int ECP_copy(EC_POINT *R, EC_POINT *P)
 	R->is_in_mont = P->is_in_mont;
 
 	return 1;
-}
+	}
+
 
 EC_POINT *ECP_dup(EC_POINT *P)
-{
+	{
 	EC_POINT *ret;
 
 	ret = ECP_new();
 	if (ret == NULL) return NULL;
 
 	if (!ECP_copy(ret, P))
-	{
+		{
 		ECP_clear_free(ret);
 		return(NULL);
-	}
+		}
 
 	return(ret);
-}
+	}
 
 
 EC_POINT *ECP_minus(EC_POINT *P, BIGNUM *p) /* mont || non-mont */
-{
+	{
 	EC_POINT *ret;
 
 	assert(P != NULL);
@@ -437,24 +446,24 @@ EC_POINT *ECP_minus(EC_POINT *P, BIGNUM *p) /* mont || non-mont */
 	if (BN_is_zero(ret->Y)) return ret;
 
 	if (!BN_sub(ret->Y, p, ret->Y))
-	{
+		{
 		ECP_clear_free(ret);
 		return NULL;
-	}
+		}
 
 	return ret;
-}
+	}
 
 
 #ifdef SIMPLE
 int ECP_cmp(EC_POINT *P, EC_POINT *Q, BIGNUM *p, BN_CTX *ctx)
-/* return values: 
+/* return values:
 	-2 ... error
-	 0 ... P = Q 
+	 0 ... P = Q
 	-1 ... P = -Q
 	 1 ... else
 */
-{
+	{
 	BIGNUM *n0, *n1, *n2, *n3, *n4;
 	int Pnorm, Qnorm;
 
@@ -477,68 +486,70 @@ int ECP_cmp(EC_POINT *P, EC_POINT *Q, BIGNUM *p, BN_CTX *ctx)
 	Pnorm = (ECP_is_norm(P));
 	Qnorm = (ECP_is_norm(Q));
 	
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	n2 = ctx->bn[ctx->tos + 2]; 
-	n3 = ctx->bn[ctx->tos + 3]; 
-	n4 = ctx->bn[ctx->tos + 4]; 
-	ctx->tos += 5;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	n2 = BN_CTX_get(ctx);
+	n3 = BN_CTX_get(ctx);
+	n4 = BN_CTX_get(ctx);
+	if (n4 == NULL) goto err;
 	
 	if (Qnorm)
-	{
+		{
 		if (BN_copy(n1, P->X) == NULL) goto err;			/* L1 = x_p */
 		if (BN_copy(n2, P->Y) == NULL) goto err;			/* L2 = y_p */
-	}
+		}
 	else
-	{
+		{
 		if (!BN_sqr(n0, Q->Z, ctx)) goto err;
 		if (!BN_mod_mul(n1, P->X, n0, p, ctx)) goto err;	/* L1 = x_p * z_q^2 */
 
-		if (!BN_mod_mul(n0, n0, Q->Z, p, ctx)) goto err; 
+		if (!BN_mod_mul(n0, n0, Q->Z, p, ctx)) goto err;
 		if (!BN_mod_mul(n2, P->Y, n0, p, ctx)) goto err;	/* L2 = y_p * z_q^3 */
-	}
+		}
 
 	if (Pnorm)
-	{
+		{
 		if (BN_copy(n3, Q->X) == NULL) goto err;			/* L3 = x_q */
 		if (BN_copy(n4, Q->Y) == NULL) goto err;			/* L4 = y_q */
-	}
+		}
 	else
-	{
+		{
 		if (!BN_sqr(n0, P->Z, ctx)) goto err;
 		if (!BN_mod_mul(n3, Q->X, n0, p, ctx)) goto err;	/* L3 = x_q * z_p^2 */
 
-		if (!BN_mod_mul(n0, n0, P->Z, p, ctx)) goto err; 
+		if (!BN_mod_mul(n0, n0, P->Z, p, ctx)) goto err;
 		if (!BN_mod_mul(n4, Q->Y, n0, p, ctx)) goto err;	/* L4 = y_q * z_p^3 */
-	}
-
+		}
+	
 	if (!BN_mod_sub(n0, n1, n3, p, ctx)) goto err;			/* L5 = L1 - L3 */
 
 	if (!BN_is_zero(n0))
-	{
-		ctx->tos -= 5;
+		{
+		BN_CTX_end(ctx);
 		return 1;
-	}
+		}
 	
 	if (!BN_mod_sub(n0, n2, n4, p, ctx)) goto err;			/* L6 = L2 - L4 */
 
 	if (!BN_is_zero(n0))
-	{
-		ctx->tos -= 5;
+		{
+		BN_CTX_end(ctx);
 		return -1;
-	}
+		}
 
-	ctx->tos -= 5;
+	BN_CTX_end(ctx);
 	return 0;
 
 err:
-	ctx->tos -= 5;
+	BN_CTX_end(ctx);
 	return -2;
-}
+	}
+
 
 int ECP_double(EC_POINT *R, EC_POINT *P, EC *E, BN_CTX *ctx)
 /* R <- 2P (on E) */
-{
+	{
 	BIGNUM *n0, *n1, *n2, *n3, *p;
 	int Pnorm, A0;
 
@@ -556,71 +567,72 @@ int ECP_double(EC_POINT *R, EC_POINT *P, EC *E, BN_CTX *ctx)
 	assert(!P->is_in_mont);
 
 	if (ECP_is_infty(P))
-	{
+		{
 		if (!BN_zero(R->Z)) return 0;
 		return 1;
-	}
+		}
 
 	Pnorm = (ECP_is_norm(P));
 	A0 = (BN_is_zero(E->A));
 
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	n2 = ctx->bn[ctx->tos + 2]; 
-	n3 = ctx->bn[ctx->tos + 3]; 
-	ctx->tos += 4;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	n2 = BN_CTX_get(ctx);
+	n3 = BN_CTX_get(ctx);
+	if (n3 == NULL) goto err;
 
 	p = E->p;
 
 	/* L1 */
 	if (Pnorm || A0)
-	{
+		{
 		if (!BN_mod_sqr(n1, P->X, p, ctx)) goto err;
-		if (!BN_mul_word(n1, 3)) goto err;  
+		if (!BN_mul_word(n1, 3)) goto err;
 		if (!A0)                                   /* if A = 0: L1 = 3 * x^2 + a * z^4 = 3 * x ^2    */
 			if (!BN_mod_add(n1, n1, E->A, p, ctx)) goto err; /* L1 = 3 * x^2 + a * z^4 = 3 * x^2 + a */
-	}
+		}
 	else
-	{
+		{
 		if (!BN_mod_sqr(n0, P->Z, p, ctx)) goto err;
 		if (!BN_mod_mul(n0, n0, n0, p, ctx)) goto err;
-		if (!BN_mod_mul(n0, n0, E->A, p, ctx)) goto err; 
+		if (!BN_mod_mul(n0, n0, E->A, p, ctx)) goto err;
 		if (!BN_mod_sqr(n1, P->X, p, ctx)) goto err;
-		if (!BN_mul_word(n1, 3)) goto err;  
+		if (!BN_mul_word(n1, 3)) goto err;
 		if (!BN_mod_add(n1, n1, n0, p, ctx)) goto err;		/* L1 = 3 * x^2 + a * z^4 */
-	}
+		}
 
 	/* Z */
 	if (Pnorm)
-	{
+		{
 		if (BN_copy(n0, P->Y) == NULL) goto err;
-	}
+		}
 	else
-	{
-		if (!BN_mod_mul(n0, P->Y, P->Z, p, ctx)) goto err; 
-	}
-	if (!BN_lshift1(n0, n0)) goto err; 
+		{
+		if (!BN_mod_mul(n0, P->Y, P->Z, p, ctx)) goto err;
+		}
+	if (!BN_lshift1(n0, n0)) goto err;
 	if (!BN_smod(R->Z, n0, p, ctx)) goto err;				/* Z = 2 * y * z */
 
 	/* L2 */
 	if (!BN_mod_sqr(n3, P->Y, p, ctx)) goto err;
-	if (!BN_mod_mul(n2, P->X, n3, p, ctx)) goto err; 
-	if (!BN_lshift(n2, n2, 2)) goto err; 
+	if (!BN_mod_mul(n2, P->X, n3, p, ctx)) goto err;
+	if (!BN_lshift(n2, n2, 2)) goto err;
 	if (!BN_smod(n2, n2, p, ctx)) goto err;					/* L2 = 4 * x * y^2 */
 
 	/* X */
-	if (!BN_lshift1(n0, n2)) goto err; 
+	if (!BN_lshift1(n0, n2)) goto err;
 	if (!BN_mod_sqr(R->X, n1, p, ctx)) goto err;
 	if (!BN_mod_sub(R->X, R->X, n0, p, ctx)) goto err;		/* X = L1^2 - 2 * L2 */
 	
 	/* L3 */
 	if (!BN_mod_sqr(n0, n3, p, ctx)) goto err;
-	if (!BN_lshift(n3, n0, 3)) goto err; 
+	if (!BN_lshift(n3, n0, 3)) goto err;
 	if (!BN_smod(n3, n3, p, ctx)) goto err;					/* L3 = 8 * y^4 */
 	
 	/* Y */
-	if (!BN_mod_sub(n0, n2, R->X, p, ctx)) goto err; 
-	if (!BN_mod_mul(n0, n1, n0, p, ctx)) goto err; 
+	if (!BN_mod_sub(n0, n2, R->X, p, ctx)) goto err;
+	if (!BN_mod_mul(n0, n1, n0, p, ctx)) goto err;
 	if (!BN_mod_sub(R->Y, n0, n3, p, ctx)) goto err;		/* Y = L1 * (L2 - X) - L3 */
 
 
@@ -628,17 +640,18 @@ int ECP_double(EC_POINT *R, EC_POINT *P, EC *E, BN_CTX *ctx)
 	if (!ECP_is_on_ec(R, E, ctx)) return 0;
 #endif
 
-	ctx->tos -= 4;
+	BN_CTX_end(ctx);
 	return 1;
 
 err:
-	ctx->tos -= 4;
+	BN_CTX_end(ctx);
 	return 0;
-}
+	}
+
 
 int ECP_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_CTX *ctx)
 /* R <- P + Q (on E) */
-{
+	{
 	BIGNUM *n0, *n1, *n2, *n3, *n4, *n5, *n6, *p;
 	int Pnorm, Qnorm;
 
@@ -668,45 +681,47 @@ int ECP_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_CTX *ctx)
 	Pnorm = (ECP_is_norm(P));
 	Qnorm = (ECP_is_norm(Q));
 	
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	n2 = ctx->bn[ctx->tos + 2]; 
-	n3 = ctx->bn[ctx->tos + 3]; 
-	n4 = ctx->bn[ctx->tos + 4]; 
-	n5 = ctx->bn[ctx->tos + 5]; 
-	n6 = ctx->bn[ctx->tos + 6]; 
-	ctx->tos += 7;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	n2 = BN_CTX_get(ctx);
+	n3 = BN_CTX_get(ctx);
+	n4 = BN_CTX_get(ctx);
+	n5 = BN_CTX_get(ctx);
+	n6 = BN_CTX_get(ctx);
+	if (n6 == NULL) goto err;
+
 	p = E->p;
 	
 	/* L1; L2 */
 	if (Qnorm)
-	{
+		{
 		if (BN_copy(n1, P->X) == NULL) goto err;         /* L1 = x_p */
 		if (BN_copy(n2, P->Y) == NULL) goto err;         /* L2 = y_p */
-	}
+		}
 	else
-	{
+		{
 		if (!BN_sqr(n0, Q->Z, ctx)) goto err;
 		if (!BN_mod_mul(n1, P->X, n0, p, ctx)) goto err; /* L1 = x_p * z_q^2 */
 
-		if (!BN_mod_mul(n0, n0, Q->Z, p, ctx)) goto err; 
+		if (!BN_mod_mul(n0, n0, Q->Z, p, ctx)) goto err;
 		if (!BN_mod_mul(n2, P->Y, n0, p, ctx)) goto err; /* L2 = y_p * z_q^3 */
-	}
+		}
 
 	/* L3; L4 */
 	if (Pnorm)
-	{
+		{
 		if (BN_copy(n3, Q->X) == NULL) goto err;         /* L3 = x_q */
 		if (BN_copy(n4, Q->Y) == NULL) goto err;         /* L4 = y_q */
-	}
+		}
 	else
-	{
+		{
 		if (!BN_sqr(n0, P->Z, ctx)) goto err;
 		if (!BN_mod_mul(n3, Q->X, n0, p, ctx)) goto err; /* L3 = x_q * z_p^2 */
 
-		if (!BN_mod_mul(n0, n0, P->Z, p, ctx)) goto err; 
+		if (!BN_mod_mul(n0, n0, P->Z, p, ctx)) goto err;
 		if (!BN_mod_mul(n4, Q->Y, n0, p, ctx)) goto err; /* L4 = y_q * z_p^3 */
-	}
+		}
 
 	/* L5; L6 */
 	if (!BN_mod_sub(n5, n1, n3, p, ctx)) goto err;		/* L5 = L1 - L3 */
@@ -714,39 +729,39 @@ int ECP_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_CTX *ctx)
 
 	/* pata */
 	if (BN_is_zero(n5))
-	{
-		if (BN_is_zero(n6))	/* P = Q => P + Q = 2P */
 		{
-			ctx->tos -= 7;
+		if (BN_is_zero(n6))	/* P = Q => P + Q = 2P */
+			{
+			BN_CTX_end(ctx);
 			return ECP_double(R, P, E, ctx);
-		}
+			}
 		else				 /* P = -Q => P + Q = \infty */
-		{ 
-			ctx->tos -= 7;
+			{
+			BN_CTX_end(ctx);
 			if (!BN_zero(R->Z)) return 0;
 			return 1;
+			}
 		}
-	}
 
 	/* L7; L8 */
 	if (!BN_mod_add(n1, n1, n3, p, ctx)) goto err;		/* L7 = L1 + L3 */
 	if (!BN_mod_add(n2, n2, n4, p, ctx)) goto err;		/* L8 = L2 + L4 */
 
 	/* Z */
-	if (Pnorm) 
-	{
+	if (Pnorm)
+		{
 		if (BN_copy(n0, Q->Z) == NULL) goto err;
-	}
+		}
 	else
-	{
+		{
 		if (!BN_mod_mul(n0, P->Z, Q->Z, p, ctx)) goto err;
-	}
+		}
 	if (!BN_mod_mul(R->Z, n0, n5, p, ctx)) goto err;	/* Z = z_p * z_q * L_5 */
 
 	/* X */
 	if (!BN_mod_sqr(n0, n6, p, ctx)) goto err;
 	if (!BN_mod_sqr(n4, n5, p, ctx)) goto err;
-	if (!BN_mod_mul(n3, n1, n4, p, ctx)) goto err; 
+	if (!BN_mod_mul(n3, n1, n4, p, ctx)) goto err;
 	if (!BN_mod_sub(R->X, n0, n3, p, ctx)) goto err;	/* X = L6^2 - L5^2 * L7 */
 	
 	/* L9 */
@@ -754,10 +769,10 @@ int ECP_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_CTX *ctx)
 	if (!BN_mod_sub(n0, n3, n0, p, ctx)) goto err;		/* L9 = L5^2 * L7 - 2X */
 
 	/* Y */
-	if (!BN_mod_mul(n0, n0, n6, p, ctx)) goto err; 
-	if (!BN_mod_mul(n5, n4, n5, p, ctx)) goto err; 
-	if (!BN_mod_mul(n1, n2, n5, p, ctx)) goto err; 
-	if (!BN_mod_sub(n0, n0, n1, p, ctx)) goto err;   
+	if (!BN_mod_mul(n0, n0, n6, p, ctx)) goto err;
+	if (!BN_mod_mul(n5, n4, n5, p, ctx)) goto err;
+	if (!BN_mod_mul(n1, n2, n5, p, ctx)) goto err;
+	if (!BN_mod_sub(n0, n0, n1, p, ctx)) goto err;
 	if (!BN_mod_mul(R->Y, n0, E->h, p, ctx)) goto err;	/* Y = (L6 * L9 - L8 * L5^3) / 2 */
 
 
@@ -766,17 +781,17 @@ int ECP_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_CTX *ctx)
 	if (!ECP_is_on_ec(R, E, ctx)) return 0;
 #endif
 
-	ctx->tos -= 7;
+	BN_CTX_end(ctx);
 	return 1;
 
 err:
-	ctx->tos -= 7;
+	BN_CTX_end(cxt);
 	return 0;
-}
+	}
 
 
 ECP_PRECOMPUTE *ECP_precompute(int r, EC_POINT *P, EC *E, BN_CTX *ctx)
-{
+	{
 	ECP_PRECOMPUTE *ret;
 	EC_POINT *P2;
 	int i, max;
@@ -807,11 +822,11 @@ ECP_PRECOMPUTE *ECP_precompute(int r, EC_POINT *P, EC *E, BN_CTX *ctx)
 
 	/* P_i = P_(i-1) + P2 */
 	for (i = 1; i < max; i++)
-	{
+		{
 		if ((ret->Pi[i] = ECP_new()) == NULL) goto err;
 		
 		if (!ECP_add(ret->Pi[i], P2, ret->Pi[i - 1], E, ctx)) goto err;
-	}
+		}
 
 	ret->r = r;
 	ECP_clear_free(P2);
@@ -822,11 +837,12 @@ err:
 	ECP_clear_free(P2);
 	ECP_clear_free_precompute(ret);
 	return NULL;
-}
+	}
+
 
 int ECP_multiply(EC_POINT *R, BIGNUM *k, ECP_PRECOMPUTE *prec, EC *E, BN_CTX *ctx)
 /* R = [k]P */
-{
+	{
 	int j;
 	int t, nextw, h, r;
 
@@ -845,11 +861,11 @@ int ECP_multiply(EC_POINT *R, BIGNUM *k, ECP_PRECOMPUTE *prec, EC *E, BN_CTX *ct
 	assert(!E->is_in_mont);
 
 	if (BN_is_zero(k))
-	{
+		{
 		if (!BN_zero(R->Z)) return 0;
 		R->is_in_mont = 0;
 		return 1;
-	}
+		}
 
 
 	j = BN_num_bits(k);
@@ -861,59 +877,57 @@ int ECP_multiply(EC_POINT *R, BIGNUM *k, ECP_PRECOMPUTE *prec, EC *E, BN_CTX *ct
 	R->is_in_mont = 0;
 
 	while(j >= 0)
-	{
-		if (!BN_is_bit_set(k, j))
 		{
+		if (!BN_is_bit_set(k, j))
+			{
 			if (!ECP_double(R, R, E, ctx)) return 0;
 			j--;
-		}
+			}
 		else
-		{
+			{
 			nextw = j - r;
 			if (nextw < -1) nextw = -1;
 			t = nextw + 1;			
 			while(!BN_is_bit_set(k, t))
-			{
 				t++;
-			}
 
 			if (!ECP_double(R, R, E, ctx)) return 0;
 
 			j--;
 			if (j < t) h = 0;
-			else 
-			{
+			else
+				{
 				h = 1;
 				for(; j > t; j--)
-				{
+					{
 					h <<= 1;
 					if (BN_is_bit_set(k, j)) h++;
 					if (!ECP_double(R, R, E, ctx)) return 0;
-				}
+					}
 				if (!ECP_double(R, R, E, ctx)) return 0;
 				j--;
-			}
+				}
 
 			if (!ECP_add(R, R, prec->Pi[h], E, ctx)) return 0;
 
 			for (; j > nextw; j--)
-			{
+				{
 				if (!ECP_double(R, R, E, ctx)) return 0;
-			}
+				}
 
+			}
 		}
-	}
-
+	
 	return 1;
-}
+	}
 
 #endif /* SIMPLE */
 
+
 #ifdef MONTGOMERY
 
 int ECP_to_montgomery(EC_POINT *P, BN_MONTGOMERY *mont, BN_CTX *ctx)
-{
-
+	{
 	assert(P != NULL);
 	assert(P->X != NULL && P->Y != NULL && P->Z != NULL);
 
@@ -935,11 +949,11 @@ int ECP_to_montgomery(EC_POINT *P, BN_MONTGOMERY *mont, BN_CTX *ctx)
 
 	P->is_in_mont = 1;
 	return 1;
-}
+	}
 
 
 int ECP_from_montgomery(EC_POINT *P, BN_MONTGOMERY *mont, BN_CTX *ctx)
-{
+	{
 
 	assert(P != NULL);
 	assert(P->X != NULL && P->Y != NULL && P->Z != NULL);
@@ -957,16 +971,17 @@ int ECP_from_montgomery(EC_POINT *P, BN_MONTGOMERY *mont, BN_CTX *ctx)
 
 	P->is_in_mont = 0;
 	return 1;
-}
+	}
+
 
-int ECP_mont_cmp(EC_POINT *P, EC_POINT *Q, BN_MONTGOMERY *mont, BN_CTX *ctx) 
-/* return values: 
+int ECP_mont_cmp(EC_POINT *P, EC_POINT *Q, BN_MONTGOMERY *mont, BN_CTX *ctx)
+/* return values:
 	-2 ... error
-	 0 ... P = Q 
+	 0 ... P = Q
 	-1 ... P = -Q
 	 1 ... else
 */
-{
+	{
 	BIGNUM *n0, *n1, *n2, *n3, *n4, *n5, *p;
 
 	assert(P != NULL);
@@ -991,13 +1006,15 @@ int ECP_mont_cmp(EC_POINT *P, EC_POINT *Q, BN_MONTGOMERY *mont, BN_CTX *ctx)
 	if (ECP_is_infty(P) || ECP_is_infty(Q)) return 1;
 
 	
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	n2 = ctx->bn[ctx->tos + 2]; 
-	n3 = ctx->bn[ctx->tos + 3]; 
-	n4 = ctx->bn[ctx->tos + 4]; 
-	n5 = ctx->bn[ctx->tos + 5]; 
-	ctx->tos += 6;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	n2 = BN_CTX_get(ctx);
+	n3 = BN_CTX_get(ctx);
+	n4 = BN_CTX_get(ctx);
+	n5 = BN_CTX_get(ctx);
+	if (n5 == 0) goto err;
+
 
 	p = mont->p;
 	
@@ -1005,44 +1022,44 @@ int ECP_mont_cmp(EC_POINT *P, EC_POINT *Q, BN_MONTGOMERY *mont, BN_CTX *ctx)
 	if (!BN_mont_mod_mul(n5, Q->Z, Q->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n1, P->X, n5, mont, ctx)) goto err;	/* L1 = x_p * z_q^2 */
 
-	if (!BN_mont_mod_mul(n0, n5, Q->Z, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n0, n5, Q->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n2, P->Y, n0, mont, ctx)) goto err;	/* L2 = y_p * z_q^3 */
 
 	if (!BN_mont_mod_mul(n5, P->Z, P->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n3, Q->X, n5, mont, ctx)) goto err;	/* L3 = x_q * z_p^2 */
 
-	if (!BN_mont_mod_mul(n0, n5, P->Z, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n0, n5, P->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n4, Q->Y, n0, mont, ctx)) goto err;	/* L4 = y_q * z_p^3 */
 
 
 	if (!BN_mod_sub_quick(n0, n1, n3, p)) goto err;			/* L5 = L1 - L3 */
 
 	if (!BN_is_zero(n0))
-	{
-		ctx->tos -= 6;
+		{
+		BN_CTX_end(ctx);
 		return 1;
-	}
+		}
 	
 	if (!BN_mod_sub_quick(n0, n2, n4, p)) goto err;			/* L6 = L2 - L4 */
 
 	if (!BN_is_zero(n0))
-	{
-		ctx->tos -= 6;
+		{
+		BN_CTX_end(ctx);
 		return -1;
-	}
+		}
 
-	ctx->tos -= 6;
+	BN_CTX_end(ctx);
 	return 0;
 
 err:
-	ctx->tos -= 6;
+	BN_CTX_end(ctx);
 	return -2;
-}
+	}
 
 
 int ECP_mont_double(EC_POINT *R, EC_POINT *P, EC *E, BN_MONTGOMERY *mont, BN_CTX *ctx)
 /* R <- 2P (on E) */
-{
+	{
 	BIGNUM *n0, *n1, *n2, *n3, *p;
 
 	assert(P != NULL);
@@ -1059,47 +1076,47 @@ int ECP_mont_double(EC_POINT *R, EC_POINT *P, EC *E, BN_MONTGOMERY *mont, BN_CTX
 	if (!P->is_in_mont)
 		if (!ECP_to_montgomery(P, mont, ctx)) return 0;
 
-	if (!E->is_in_mont) 
+	if (!E->is_in_mont)
 		if (!EC_to_montgomery(E, mont, ctx)) return 0;
 
 	R->is_in_mont = 1;
 
 	if (ECP_is_infty(P))
-	{
+		{
 		if (!BN_zero(R->Z)) return 0;
 		return 1;
-	}
-
+		}
 
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	n2 = ctx->bn[ctx->tos + 2]; 
-	n3 = ctx->bn[ctx->tos + 3]; 
 
-	ctx->tos += 4;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	n2 = BN_CTX_get(ctx);
+	n3 = BN_CTX_get(ctx);
+	if (n3 == 0) goto err;
 
 	p = E->p;
 
 	/* L1 */
 	if (!BN_mont_mod_mul(n0, P->Z, P->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n2, n0, n0, mont, ctx)) goto err;
-	if (!BN_mont_mod_mul(n0, n2, E->A, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n0, n2, E->A, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n1, P->X, P->X, mont, ctx)) goto err;
 	if (!BN_mod_lshift1_quick(n2, n1, p)) goto err;
 	if (!BN_mod_add_quick(n1, n1, n2, p)) goto err;
 	if (!BN_mod_add_quick(n1, n1, n0, p)) goto err;		/* L1 = 3 * x^2 + a * z^4 */
 
 	/* Z */
-	if (!BN_mont_mod_mul(n0, P->Y, P->Z, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n0, P->Y, P->Z, mont, ctx)) goto err;
 	if (!BN_mod_lshift1_quick(R->Z, n0, p)) goto err;		/* Z = 2 * y * z */
 
 	/* L2 */
 	if (!BN_mont_mod_mul(n3, P->Y, P->Y, mont, ctx)) goto err;
-	if (!BN_mont_mod_mul(n2, P->X, n3, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n2, P->X, n3, mont, ctx)) goto err;
 	if (!BN_mod_lshift_quick(n2, n2, 2, p)) goto err;		/* L2 = 4 * x * y^2 */
 
 	/* X */
-	if (!BN_mod_lshift1_quick(n0, n2, p)) goto err; 
+	if (!BN_mod_lshift1_quick(n0, n2, p)) goto err;
 	if (!BN_mont_mod_mul(R->X, n1, n1, mont, ctx)) goto err;
 	if (!BN_mod_sub_quick(R->X, R->X, n0, p)) goto err;	/* X = L1^2 - 2 * L2 */
 	
@@ -1109,22 +1126,22 @@ int ECP_mont_double(EC_POINT *R, EC_POINT *P, EC *E, BN_MONTGOMERY *mont, BN_CTX
 
 	
 	/* Y */
-	if (!BN_mod_sub_quick(n2, n2, R->X, p)) goto err; 
-	if (!BN_mont_mod_mul(n0, n1, n2, mont, ctx)) goto err; 
+	if (!BN_mod_sub_quick(n2, n2, R->X, p)) goto err;
+	if (!BN_mont_mod_mul(n0, n1, n2, mont, ctx)) goto err;
 	if (!BN_mod_sub_quick(R->Y, n0, n3, p)) goto err;		/* Y = L1 * (L2 - X) - L3 */
 
-	ctx->tos -= 4;
+	BN_CTX_end(ctx);
 	return 1;
 
 err:
-	ctx->tos -= 4;
+	BN_CTX_end(ctx);
 	return 0;
-}
+	}
 
 
 int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mont, BN_CTX *ctx)
 /* R <- P + Q (on E) */
-{
+	{
 	BIGNUM *n0, *n1, *n2, *n3, *n4, *n5, *n6, *p;
 
 	assert(P != NULL);
@@ -1148,7 +1165,7 @@ int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mo
 	if (!P->is_in_mont)
 		if (!ECP_to_montgomery(P, mont, ctx)) return 0;
 
-	if (!E->is_in_mont) 
+	if (!E->is_in_mont)
 		if (!EC_to_montgomery(E, mont, ctx)) return 0;
 
 	if (P == Q) return ECP_mont_double(R, P, E, mont, ctx);
@@ -1157,14 +1174,15 @@ int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mo
 	if (ECP_is_infty(Q)) return ECP_copy(R, P);
 	
 
-	n0 = ctx->bn[ctx->tos]; 
-	n1 = ctx->bn[ctx->tos + 1]; 
-	n2 = ctx->bn[ctx->tos + 2]; 
-	n3 = ctx->bn[ctx->tos + 3]; 
-	n4 = ctx->bn[ctx->tos + 4]; 
-	n5 = ctx->bn[ctx->tos + 5]; 
-	n6 = ctx->bn[ctx->tos + 6]; 
-	ctx->tos += 7;
+	BN_CTX_start(ctx);
+	n0 = BN_CTX_get(ctx);
+	n1 = BN_CTX_get(ctx);
+	n2 = BN_CTX_get(ctx);
+	n3 = BN_CTX_get(ctx);
+	n4 = BN_CTX_get(ctx);
+	n5 = BN_CTX_get(ctx);
+	n6 = BN_CTX_get(ctx);
+	if (n6 == NULL) goto err;
 
 
 	p = E->p;
@@ -1175,7 +1193,7 @@ int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mo
 	if (!BN_mont_mod_mul(n6, Q->Z, Q->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n1, P->X, n6, mont, ctx)) goto err;	/* L1 = x_p * z_q^2 */
 
-	if (!BN_mont_mod_mul(n0, n6, Q->Z, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n0, n6, Q->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n2, P->Y, n0, mont, ctx)) goto err;	/* L2 = y_p * z_q^3 */
 
 
@@ -1183,7 +1201,7 @@ int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mo
 	if (!BN_mont_mod_mul(n6, P->Z, P->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n3, Q->X, n6, mont, ctx)) goto err;	/* L3 = x_q * z_p^2 */
 
-	if (!BN_mont_mod_mul(n0, n6, P->Z, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n0, n6, P->Z, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n4, Q->Y, n0, mont, ctx)) goto err;	/* L4 = y_q * z_p^3 */
 
 
@@ -1194,19 +1212,19 @@ int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mo
 
 	/* pata */
 	if (BN_is_zero(n5))
-	{
-		if (BN_is_zero(n6))  /* P = Q => P + Q = 2P */
 		{
-			ctx->tos -= 7;
+		if (BN_is_zero(n6))  /* P = Q => P + Q = 2P */
+			{
+			BN_CTX_end(ctx);
 			return ECP_mont_double(R, P, E, mont, ctx);
-		}
+			}
 		else				 /* P = -Q => P + Q = \infty */
-		{ 
-			ctx->tos -= 7;
+			{
+			BN_CTX_end(ctx);
 			if (!BN_zero(R->Z)) return 0;
 			return 1;
+			}
 		}
-	}
 
 	/* L7; L8 */
 	if (!BN_mod_add_quick(n1, n1, n3, p)) goto err;			/* L7 = L1 + L3 */
@@ -1221,7 +1239,7 @@ int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mo
 	/* X */
 	if (!BN_mont_mod_mul(n0, n6, n6, mont, ctx)) goto err;
 	if (!BN_mont_mod_mul(n4, n5, n5, mont, ctx)) goto err;
-	if (!BN_mont_mod_mul(n3, n1, n4, mont, ctx)) goto err; 
+	if (!BN_mont_mod_mul(n3, n1, n4, mont, ctx)) goto err;
 	if (!BN_mod_sub_quick(R->X, n0, n3, p)) goto err;			/* X = L6^2 - L5^2 * L7 */
 
 	
@@ -1231,24 +1249,24 @@ int ECP_mont_add(EC_POINT *R, EC_POINT *P, EC_POINT *Q, EC *E, BN_MONTGOMERY *mo
 
 
 	/* Y */
-	if (!BN_mont_mod_mul(n0, n3, n6, mont, ctx)) goto err; 
-	if (!BN_mont_mod_mul(n6, n4, n5, mont, ctx)) goto err; 
-	if (!BN_mont_mod_mul(n1, n2, n6, mont, ctx)) goto err; 
-	if (!BN_mod_sub_quick(n0, n0, n1, p)) goto err;   
+	if (!BN_mont_mod_mul(n0, n3, n6, mont, ctx)) goto err;
+	if (!BN_mont_mod_mul(n6, n4, n5, mont, ctx)) goto err;
+	if (!BN_mont_mod_mul(n1, n2, n6, mont, ctx)) goto err;
+	if (!BN_mod_sub_quick(n0, n0, n1, p)) goto err;
 	if (!BN_mont_mod_mul(R->Y, n0, E->h, mont, ctx)) goto err;	/* Y = (L6 * L9 - L8 * L5^3) / 2 */
 
 
-	ctx->tos -= 7;
+	BN_CTX_end(ctx);
 	return 1;
 
 err:
-	ctx->tos -= 7;
+	BN_CTX_end(ctx);
 	return 0;
-}
+	}
 
 
 ECP_PRECOMPUTE *ECP_mont_precompute(int r, EC_POINT *P, EC *E, BN_MONTGOMERY *mont, BN_CTX *ctx)
-{
+	{
 	ECP_PRECOMPUTE *ret;
 	EC_POINT *P2;
 	int i, max;
@@ -1262,7 +1280,7 @@ ECP_PRECOMPUTE *ECP_mont_precompute(int r, EC_POINT *P, EC *E, BN_MONTGOMERY *mo
 	if (!P->is_in_mont)
 		if (!ECP_to_montgomery(P, mont, ctx)) return 0;
 
-	if (!E->is_in_mont) 
+	if (!E->is_in_mont)
 		if (!EC_to_montgomery(E, mont, ctx)) return 0;
 
 	ret=(ECP_PRECOMPUTE *)malloc(sizeof(ECP_PRECOMPUTE));
@@ -1287,10 +1305,10 @@ ECP_PRECOMPUTE *ECP_mont_precompute(int r, EC_POINT *P, EC *E, BN_MONTGOMERY *mo
 
 	/* P_i = P_(i-1) + P2 */
 	for (i = 1; i < max; i++)
-	{
+		{
 		if ((ret->Pi[i] = ECP_new()) == NULL) goto err;
 		if (!ECP_mont_add(ret->Pi[i], P2, ret->Pi[i - 1], E, mont, ctx)) goto err;
-	}
+		}
 
 	ret->r = r;
 	ECP_clear_free(P2);
@@ -1301,11 +1319,12 @@ err:
 	ECP_clear_free(P2);
 	ECP_clear_free_precompute(ret);
 	return NULL;
-}
+	}
+
 
 int ECP_mont_multiply(EC_POINT *R, BIGNUM *k, ECP_PRECOMPUTE *prec, EC *E, BN_MONTGOMERY *mont, BN_CTX *ctx)
 /* R = [k]P   P = prec->Pi[0]*/
-{
+	{
 	int j;
 	int t, nextw, h, r;
 
@@ -1324,16 +1343,16 @@ int ECP_mont_multiply(EC_POINT *R, BIGNUM *k, ECP_PRECOMPUTE *prec, EC *E, BN_MO
 	assert(mont != NULL);
 	assert(mont->p != NULL);
 
-	if (!E->is_in_mont) 
+	if (!E->is_in_mont)
 		if (!EC_to_montgomery(E, mont, ctx)) return 0;
 
 
 	if (BN_is_zero(k))
-	{
+		{
 		if (!BN_zero(R->Z)) return 0;
 		R->is_in_mont = 1;
 		return 1;
-	}
+		}
 
 	j = BN_num_bits(k);
 	j--;
@@ -1344,56 +1363,54 @@ int ECP_mont_multiply(EC_POINT *R, BIGNUM *k, ECP_PRECOMPUTE *prec, EC *E, BN_MO
 	R->is_in_mont = 1;
 
 	while(j >= 0)
-	{
-		if (!BN_is_bit_set(k, j))
 		{
+		if (!BN_is_bit_set(k, j))
+			{
 			if (!ECP_mont_double(R, R, E, mont, ctx)) return 0;
 			j--;
-		}
+			}
 		else
-		{
+			{
 			nextw = j - r;
 			if (nextw < -1) nextw = -1;
 			t = nextw + 1;			
 			while(!BN_is_bit_set(k, t))
-			{
 				t++;
-			}
 
 			if (!ECP_mont_double(R, R, E, mont, ctx)) return 0;
 
 			j--;
 			if (j < t) h = 0;
-			else 
-			{
+			else
+				{
 				h = 1;
 				for(; j > t; j--)
-				{
+					{
 					h <<= 1;
 					if (BN_is_bit_set(k, j)) h++;
 					if (!ECP_mont_double(R, R, E, mont, ctx)) return 0;
-				}
+					}
 				if (!ECP_mont_double(R, R, E, mont, ctx)) return 0;
 				j--;
-			}
+				}
 
 			if (!ECP_mont_add(R, R, prec->Pi[h], E, mont, ctx)) return 0;
 
 			for (; j > nextw; j--)
-			{
+				{
 				if (!ECP_mont_double(R, R, E, mont, ctx)) return 0;
-			}
+				}
 
+			}
 		}
-	}
 
 	return 1;
-}
+	}
 
 
 int ECP_mont_multiply2(EC_POINT *R, BIGNUM *k, EC_POINT *P, EC *E, BN_MONTGOMERY *mont, BN_CTX *ctx)
 /* R = [k]P */
-{
+	{
 	int j, hj, kj;
 	BIGNUM *h;
 	EC_POINT *mP;
@@ -1415,19 +1432,19 @@ int ECP_mont_multiply2(EC_POINT *R, BIGNUM *k, EC_POINT *P, EC *E, BN_MONTGOMERY
 	assert(mont != NULL);
 	assert(mont->p != NULL);
 
-	if (!E->is_in_mont) 
+	if (!E->is_in_mont)
 		if (!EC_to_montgomery(E, mont, ctx)) return 0;
 
-	if (!P->is_in_mont) 
+	if (!P->is_in_mont)
 		if (!ECP_to_montgomery(P, mont, ctx)) return 0;
 
 
 	if (BN_is_zero(k))
-	{
+		{
 		if (!BN_zero(R->Z)) return 0;
 		R->is_in_mont = 1;
 		return 1;
-	}
+		}
 
 	if ((h = BN_dup(k)) == NULL) return 0;
 	
@@ -1438,7 +1455,7 @@ int ECP_mont_multiply2(EC_POINT *R, BIGNUM *k, EC_POINT *P, EC *E, BN_MONTGOMERY
 	if ((mP = ECP_mont_minus(P, mont)) == NULL) goto err;
 
 	for(j = BN_num_bits(h) - 2; j > 0; j--)
-	{
+		{
 		if (!ECP_mont_double(R, R, E, mont, ctx)) goto err;
 		kj = BN_is_bit_set(k, j);
 		hj = BN_is_bit_set(h, j);
@@ -1446,7 +1463,7 @@ int ECP_mont_multiply2(EC_POINT *R, BIGNUM *k, EC_POINT *P, EC *E, BN_MONTGOMERY
 			if (!ECP_mont_add(R, R, P, E, mont, ctx)) goto err;
 		if (hj == 0 && kj == 1)
 			if (!ECP_mont_add(R, R, mP, E, mont, ctx)) goto err;
-	}
+		}
 
 	if (h != NULL) BN_free(h);
 	if (mP != NULL) ECP_clear_free(mP);
@@ -1456,6 +1473,6 @@ err:
 	if (h != NULL) BN_free(h);
 	if (mP != NULL) ECP_clear_free(mP);
 	return 0;
-}
+	}
 
 #endif /* MONTGOMERY */