add missing group element invariant checks
The group element checks `secp256k1_{ge,gej}_verify` have first been
implemented and added in commit f20266722ac93ca66d1beb0d2f2d2469b95aafea
(PR #1299). This commit adds additional verification calls in group
functions, to match the ones that were originally proposed in commit
09dbba561fdb9d57a2cc9842ce041d9ba29a6189 of WIP-PR #1032 (which is
obviously not rebased on #1299 yet).
Also, for easier review, all functions handling group elements are
structured in the following wasy for easier review (idea suggested by
Tim Ruffing):
- on entry, verify all input ge, gej (and fe)
- empty line
- actual function body
- empty line
- on exit, verify all output ge, gej
Co-authored-by: Peter Dettman <peter.dettman@gmail.com>
Co-authored-by: Tim Ruffing <crypto@timruffing.de>
This commit is contained in:
Sebastian Falbesoner
parent
c545fdc374
commit
690b0fc05a
102
src/group_impl.h
102
src/group_impl.h
@ -99,11 +99,13 @@ static void secp256k1_ge_set_gej_zinv(secp256k1_ge *r, const secp256k1_gej *a, c
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secp256k1_gej_verify(a);
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secp256k1_fe_verify(zi);
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VERIFY_CHECK(!a->infinity);
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secp256k1_fe_sqr(&zi2, zi);
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secp256k1_fe_mul(&zi3, &zi2, zi);
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secp256k1_fe_mul(&r->x, &a->x, &zi2);
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secp256k1_fe_mul(&r->y, &a->y, &zi3);
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r->infinity = a->infinity;
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secp256k1_ge_verify(r);
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}
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@ -114,39 +116,47 @@ static void secp256k1_ge_set_ge_zinv(secp256k1_ge *r, const secp256k1_ge *a, con
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secp256k1_ge_verify(a);
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secp256k1_fe_verify(zi);
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VERIFY_CHECK(!a->infinity);
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secp256k1_fe_sqr(&zi2, zi);
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secp256k1_fe_mul(&zi3, &zi2, zi);
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secp256k1_fe_mul(&r->x, &a->x, &zi2);
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secp256k1_fe_mul(&r->y, &a->y, &zi3);
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r->infinity = a->infinity;
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secp256k1_ge_verify(r);
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}
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static void secp256k1_ge_set_xy(secp256k1_ge *r, const secp256k1_fe *x, const secp256k1_fe *y) {
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secp256k1_fe_verify(x);
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secp256k1_fe_verify(y);
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r->infinity = 0;
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r->x = *x;
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r->y = *y;
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secp256k1_ge_verify(r);
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}
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static int secp256k1_ge_is_infinity(const secp256k1_ge *a) {
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secp256k1_ge_verify(a);
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return a->infinity;
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}
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static void secp256k1_ge_neg(secp256k1_ge *r, const secp256k1_ge *a) {
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secp256k1_ge_verify(a);
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*r = *a;
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secp256k1_fe_normalize_weak(&r->y);
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secp256k1_fe_negate(&r->y, &r->y, 1);
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secp256k1_ge_verify(r);
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}
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static void secp256k1_ge_set_gej(secp256k1_ge *r, secp256k1_gej *a) {
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secp256k1_fe z2, z3;
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secp256k1_gej_verify(a);
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r->infinity = a->infinity;
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secp256k1_fe_inv(&a->z, &a->z);
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secp256k1_fe_sqr(&z2, &a->z);
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@ -156,12 +166,15 @@ static void secp256k1_ge_set_gej(secp256k1_ge *r, secp256k1_gej *a) {
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secp256k1_fe_set_int(&a->z, 1);
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r->x = a->x;
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r->y = a->y;
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secp256k1_gej_verify(a);
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secp256k1_ge_verify(r);
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}
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static void secp256k1_ge_set_gej_var(secp256k1_ge *r, secp256k1_gej *a) {
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secp256k1_fe z2, z3;
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secp256k1_gej_verify(a);
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if (secp256k1_gej_is_infinity(a)) {
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secp256k1_ge_set_infinity(r);
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return;
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@ -174,6 +187,8 @@ static void secp256k1_ge_set_gej_var(secp256k1_ge *r, secp256k1_gej *a) {
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secp256k1_fe_mul(&a->y, &a->y, &z3);
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secp256k1_fe_set_int(&a->z, 1);
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secp256k1_ge_set_xy(r, &a->x, &a->y);
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secp256k1_gej_verify(a);
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secp256k1_ge_verify(r);
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}
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@ -181,9 +196,13 @@ static void secp256k1_ge_set_all_gej_var(secp256k1_ge *r, const secp256k1_gej *a
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secp256k1_fe u;
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size_t i;
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size_t last_i = SIZE_MAX;
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#ifdef VERIFY
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for (i = 0; i < len; i++) {
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secp256k1_gej_verify(&a[i]);
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}
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#endif
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for (i = 0; i < len; i++) {
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if (a[i].infinity) {
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secp256k1_ge_set_infinity(&r[i]);
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} else {
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@ -217,36 +236,46 @@ static void secp256k1_ge_set_all_gej_var(secp256k1_ge *r, const secp256k1_gej *a
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if (!a[i].infinity) {
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secp256k1_ge_set_gej_zinv(&r[i], &a[i], &r[i].x);
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}
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}
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#ifdef VERIFY
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for (i = 0; i < len; i++) {
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secp256k1_ge_verify(&r[i]);
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}
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#endif
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}
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static void secp256k1_ge_table_set_globalz(size_t len, secp256k1_ge *a, const secp256k1_fe *zr) {
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size_t i = len - 1;
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size_t i;
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secp256k1_fe zs;
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if (len > 0) {
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/* Verify inputs a[len-1] and zr[len-1]. */
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#ifdef VERIFY
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for (i = 0; i < len; i++) {
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secp256k1_ge_verify(&a[i]);
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secp256k1_fe_verify(&zr[i]);
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}
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#endif
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if (len > 0) {
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i = len - 1;
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/* Ensure all y values are in weak normal form for fast negation of points */
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secp256k1_fe_normalize_weak(&a[i].y);
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zs = zr[i];
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/* Work our way backwards, using the z-ratios to scale the x/y values. */
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while (i > 0) {
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/* Verify all inputs a[i] and zr[i]. */
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secp256k1_fe_verify(&zr[i]);
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secp256k1_ge_verify(&a[i]);
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if (i != len - 1) {
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secp256k1_fe_mul(&zs, &zs, &zr[i]);
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}
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i--;
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secp256k1_ge_set_ge_zinv(&a[i], &a[i], &zs);
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/* Verify the output a[i]. */
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secp256k1_ge_verify(&a[i]);
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}
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}
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#ifdef VERIFY
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for (i = 0; i < len; i++) {
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secp256k1_ge_verify(&a[i]);
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}
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#endif
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}
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static void secp256k1_gej_set_infinity(secp256k1_gej *r) {
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@ -254,6 +283,7 @@ static void secp256k1_gej_set_infinity(secp256k1_gej *r) {
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secp256k1_fe_clear(&r->x);
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secp256k1_fe_clear(&r->y);
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secp256k1_fe_clear(&r->z);
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secp256k1_gej_verify(r);
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}
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@ -261,6 +291,7 @@ static void secp256k1_ge_set_infinity(secp256k1_ge *r) {
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r->infinity = 1;
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secp256k1_fe_clear(&r->x);
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secp256k1_fe_clear(&r->y);
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secp256k1_ge_verify(r);
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}
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@ -269,18 +300,23 @@ static void secp256k1_gej_clear(secp256k1_gej *r) {
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secp256k1_fe_clear(&r->x);
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secp256k1_fe_clear(&r->y);
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secp256k1_fe_clear(&r->z);
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secp256k1_gej_verify(r);
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}
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static void secp256k1_ge_clear(secp256k1_ge *r) {
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r->infinity = 0;
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secp256k1_fe_clear(&r->x);
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secp256k1_fe_clear(&r->y);
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secp256k1_ge_verify(r);
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}
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static int secp256k1_ge_set_xo_var(secp256k1_ge *r, const secp256k1_fe *x, int odd) {
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secp256k1_fe x2, x3;
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int ret;
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secp256k1_fe_verify(x);
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r->x = *x;
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secp256k1_fe_sqr(&x2, x);
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secp256k1_fe_mul(&x3, x, &x2);
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@ -291,16 +327,19 @@ static int secp256k1_ge_set_xo_var(secp256k1_ge *r, const secp256k1_fe *x, int o
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if (secp256k1_fe_is_odd(&r->y) != odd) {
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secp256k1_fe_negate(&r->y, &r->y, 1);
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}
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secp256k1_ge_verify(r);
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return ret;
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}
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static void secp256k1_gej_set_ge(secp256k1_gej *r, const secp256k1_ge *a) {
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secp256k1_ge_verify(a);
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r->infinity = a->infinity;
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r->x = a->x;
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r->y = a->y;
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secp256k1_fe_set_int(&r->z, 1);
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secp256k1_gej_verify(r);
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}
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@ -308,6 +347,7 @@ static int secp256k1_gej_eq_var(const secp256k1_gej *a, const secp256k1_gej *b)
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secp256k1_gej tmp;
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secp256k1_gej_verify(b);
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secp256k1_gej_verify(a);
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secp256k1_gej_neg(&tmp, a);
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secp256k1_gej_add_var(&tmp, &tmp, b, NULL);
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return secp256k1_gej_is_infinity(&tmp);
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@ -315,11 +355,10 @@ static int secp256k1_gej_eq_var(const secp256k1_gej *a, const secp256k1_gej *b)
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static int secp256k1_gej_eq_x_var(const secp256k1_fe *x, const secp256k1_gej *a) {
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secp256k1_fe r;
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#ifdef VERIFY
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secp256k1_fe_verify(x);
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VERIFY_CHECK(a->x.magnitude <= 31);
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secp256k1_gej_verify(a);
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#ifdef VERIFY
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VERIFY_CHECK(a->x.magnitude <= 31);
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VERIFY_CHECK(!a->infinity);
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#endif
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@ -329,23 +368,27 @@ static int secp256k1_gej_eq_x_var(const secp256k1_fe *x, const secp256k1_gej *a)
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static void secp256k1_gej_neg(secp256k1_gej *r, const secp256k1_gej *a) {
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secp256k1_gej_verify(a);
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r->infinity = a->infinity;
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r->x = a->x;
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r->y = a->y;
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r->z = a->z;
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secp256k1_fe_normalize_weak(&r->y);
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secp256k1_fe_negate(&r->y, &r->y, 1);
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secp256k1_gej_verify(r);
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}
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static int secp256k1_gej_is_infinity(const secp256k1_gej *a) {
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secp256k1_gej_verify(a);
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return a->infinity;
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}
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static int secp256k1_ge_is_valid_var(const secp256k1_ge *a) {
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secp256k1_fe y2, x3;
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secp256k1_ge_verify(a);
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if (a->infinity) {
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return 0;
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}
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@ -359,8 +402,8 @@ static int secp256k1_ge_is_valid_var(const secp256k1_ge *a) {
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static SECP256K1_INLINE void secp256k1_gej_double(secp256k1_gej *r, const secp256k1_gej *a) {
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/* Operations: 3 mul, 4 sqr, 8 add/half/mul_int/negate */
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secp256k1_fe l, s, t;
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secp256k1_gej_verify(a);
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r->infinity = a->infinity;
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/* Formula used:
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@ -387,10 +430,13 @@ static SECP256K1_INLINE void secp256k1_gej_double(secp256k1_gej *r, const secp25
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secp256k1_fe_mul(&r->y, &t, &l); /* Y3 = L*(X3 + T) (1) */
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secp256k1_fe_add(&r->y, &s); /* Y3 = L*(X3 + T) + S^2 (2) */
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secp256k1_fe_negate(&r->y, &r->y, 2); /* Y3 = -(L*(X3 + T) + S^2) (3) */
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secp256k1_gej_verify(r);
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}
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static void secp256k1_gej_double_var(secp256k1_gej *r, const secp256k1_gej *a, secp256k1_fe *rzr) {
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secp256k1_gej_verify(a);
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/** For secp256k1, 2Q is infinity if and only if Q is infinity. This is because if 2Q = infinity,
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* Q must equal -Q, or that Q.y == -(Q.y), or Q.y is 0. For a point on y^2 = x^3 + 7 to have
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* y=0, x^3 must be -7 mod p. However, -7 has no cube root mod p.
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@ -401,7 +447,6 @@ static void secp256k1_gej_double_var(secp256k1_gej *r, const secp256k1_gej *a, s
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* the infinity flag even though the point doubles to infinity, and the result
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* point will be gibberish (z = 0 but infinity = 0).
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*/
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secp256k1_gej_verify(a);
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if (a->infinity) {
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secp256k1_gej_set_infinity(r);
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if (rzr != NULL) {
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@ -416,15 +461,16 @@ static void secp256k1_gej_double_var(secp256k1_gej *r, const secp256k1_gej *a, s
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}
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secp256k1_gej_double(r, a);
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secp256k1_gej_verify(r);
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}
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static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_gej *b, secp256k1_fe *rzr) {
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/* 12 mul, 4 sqr, 11 add/negate/normalizes_to_zero (ignoring special cases) */
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secp256k1_fe z22, z12, u1, u2, s1, s2, h, i, h2, h3, t;
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secp256k1_gej_verify(a);
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secp256k1_gej_verify(b);
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if (a->infinity) {
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VERIFY_CHECK(rzr == NULL);
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*r = *b;
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@ -479,6 +525,7 @@ static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, cons
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secp256k1_fe_mul(&r->y, &t, &i);
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secp256k1_fe_mul(&h3, &h3, &s1);
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secp256k1_fe_add(&r->y, &h3);
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secp256k1_gej_verify(r);
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}
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@ -487,6 +534,7 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
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secp256k1_fe z12, u1, u2, s1, s2, h, i, h2, h3, t;
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secp256k1_gej_verify(a);
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secp256k1_ge_verify(b);
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if (a->infinity) {
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VERIFY_CHECK(rzr == NULL);
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secp256k1_gej_set_ge(r, b);
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@ -539,6 +587,7 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
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secp256k1_fe_mul(&r->y, &t, &i);
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secp256k1_fe_mul(&h3, &h3, &s1);
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secp256k1_fe_add(&r->y, &h3);
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secp256k1_gej_verify(r);
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if (rzr != NULL) secp256k1_fe_verify(rzr);
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}
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@ -546,9 +595,10 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
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static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_ge *b, const secp256k1_fe *bzinv) {
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/* 9 mul, 3 sqr, 13 add/negate/normalize_weak/normalizes_to_zero (ignoring special cases) */
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secp256k1_fe az, z12, u1, u2, s1, s2, h, i, h2, h3, t;
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secp256k1_gej_verify(a);
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secp256k1_ge_verify(b);
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secp256k1_fe_verify(bzinv);
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if (a->infinity) {
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secp256k1_fe bzinv2, bzinv3;
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r->infinity = b->infinity;
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@ -557,6 +607,7 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
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secp256k1_fe_mul(&r->x, &b->x, &bzinv2);
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secp256k1_fe_mul(&r->y, &b->y, &bzinv3);
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secp256k1_fe_set_int(&r->z, 1);
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secp256k1_gej_verify(r);
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return;
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}
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if (b->infinity) {
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@ -607,6 +658,7 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
|
||||
secp256k1_fe_mul(&r->y, &t, &i);
|
||||
secp256k1_fe_mul(&h3, &h3, &s1);
|
||||
secp256k1_fe_add(&r->y, &h3);
|
||||
|
||||
secp256k1_gej_verify(r);
|
||||
}
|
||||
|
||||
@ -743,6 +795,7 @@ static void secp256k1_gej_add_ge(secp256k1_gej *r, const secp256k1_gej *a, const
|
||||
* We have degenerate = false, r->z = (y1 + y2) * Z.
|
||||
* Then r->infinity = ((y1 + y2)Z == 0) = (y1 == -y2) = false. */
|
||||
r->infinity = secp256k1_fe_normalizes_to_zero(&r->z);
|
||||
|
||||
secp256k1_gej_verify(r);
|
||||
}
|
||||
|
||||
@ -754,11 +807,13 @@ static void secp256k1_gej_rescale(secp256k1_gej *r, const secp256k1_fe *s) {
|
||||
#ifdef VERIFY
|
||||
VERIFY_CHECK(!secp256k1_fe_normalizes_to_zero_var(s));
|
||||
#endif
|
||||
|
||||
secp256k1_fe_sqr(&zz, s);
|
||||
secp256k1_fe_mul(&r->x, &r->x, &zz); /* r->x *= s^2 */
|
||||
secp256k1_fe_mul(&r->y, &r->y, &zz);
|
||||
secp256k1_fe_mul(&r->y, &r->y, s); /* r->y *= s^3 */
|
||||
secp256k1_fe_mul(&r->z, &r->z, s); /* r->z *= s */
|
||||
|
||||
secp256k1_gej_verify(r);
|
||||
}
|
||||
|
||||
@ -766,6 +821,7 @@ static void secp256k1_ge_to_storage(secp256k1_ge_storage *r, const secp256k1_ge
|
||||
secp256k1_fe x, y;
|
||||
secp256k1_ge_verify(a);
|
||||
VERIFY_CHECK(!a->infinity);
|
||||
|
||||
x = a->x;
|
||||
secp256k1_fe_normalize(&x);
|
||||
y = a->y;
|
||||
@ -778,17 +834,19 @@ static void secp256k1_ge_from_storage(secp256k1_ge *r, const secp256k1_ge_storag
|
||||
secp256k1_fe_from_storage(&r->x, &a->x);
|
||||
secp256k1_fe_from_storage(&r->y, &a->y);
|
||||
r->infinity = 0;
|
||||
|
||||
secp256k1_ge_verify(r);
|
||||
}
|
||||
|
||||
static SECP256K1_INLINE void secp256k1_gej_cmov(secp256k1_gej *r, const secp256k1_gej *a, int flag) {
|
||||
secp256k1_gej_verify(r);
|
||||
secp256k1_gej_verify(a);
|
||||
|
||||
secp256k1_fe_cmov(&r->x, &a->x, flag);
|
||||
secp256k1_fe_cmov(&r->y, &a->y, flag);
|
||||
secp256k1_fe_cmov(&r->z, &a->z, flag);
|
||||
|
||||
r->infinity ^= (r->infinity ^ a->infinity) & flag;
|
||||
|
||||
secp256k1_gej_verify(r);
|
||||
}
|
||||
|
||||
@ -798,9 +856,11 @@ static SECP256K1_INLINE void secp256k1_ge_storage_cmov(secp256k1_ge_storage *r,
|
||||
}
|
||||
|
||||
static void secp256k1_ge_mul_lambda(secp256k1_ge *r, const secp256k1_ge *a) {
|
||||
*r = *a;
|
||||
secp256k1_ge_verify(a);
|
||||
|
||||
*r = *a;
|
||||
secp256k1_fe_mul(&r->x, &r->x, &secp256k1_const_beta);
|
||||
|
||||
secp256k1_ge_verify(r);
|
||||
}
|
||||
|
||||
@ -808,8 +868,8 @@ static int secp256k1_ge_is_in_correct_subgroup(const secp256k1_ge* ge) {
|
||||
#ifdef EXHAUSTIVE_TEST_ORDER
|
||||
secp256k1_gej out;
|
||||
int i;
|
||||
|
||||
secp256k1_ge_verify(ge);
|
||||
|
||||
/* A very simple EC multiplication ladder that avoids a dependency on ecmult. */
|
||||
secp256k1_gej_set_infinity(&out);
|
||||
for (i = 0; i < 32; ++i) {
|
||||
@ -820,6 +880,8 @@ static int secp256k1_ge_is_in_correct_subgroup(const secp256k1_ge* ge) {
|
||||
}
|
||||
return secp256k1_gej_is_infinity(&out);
|
||||
#else
|
||||
secp256k1_ge_verify(ge);
|
||||
|
||||
(void)ge;
|
||||
/* The real secp256k1 group has cofactor 1, so the subgroup is the entire curve. */
|
||||
return 1;
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user