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Make pubkey parsing test whether points are in the correct subgroup

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Pieter Wuille
2020-09-07 18:23:52 -07:00
parent 87af00b511
commit 08d7d89299
4 changed files with 38 additions and 0 deletions
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11
src/group.h
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@@ -139,4 +139,15 @@ static void secp256k1_ge_storage_cmov(secp256k1_ge_storage *r, const secp256k1_g
/** Rescale a jacobian point by b which must be non-zero. Constant-time. */
static void secp256k1_gej_rescale(secp256k1_gej *r, const secp256k1_fe *b);
/** Determine if a point (which is assumed to be on the curve) is in the correct (sub)group of the curve.
*
* In normal mode, the used group is secp256k1, which has cofactor=1 meaning that every point on the curve is in the
* group, and this function returns always true.
*
* When compiling in exhaustive test mode, a slightly different curve equation is used, leading to a group with a
* (very) small subgroup, and that subgroup is what is used for all cryptographic operations. In that mode, this
* function checks whether a point that is on the curve is in fact also in that subgroup.
*/
static int secp256k1_ge_is_in_correct_subgroup(const secp256k1_ge* ge);
#endif /* SECP256K1_GROUP_H */