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c-kzg-4844
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Sanity check that trusted setup was loaded in Lagrange form (#309) 

* Sanity check that trusted setup was loaded in Lagrange form

* fixup! Sanity check that trusted setup was loaded in Lagrange form

* Fix some nits

* Fix another nit

---------

Co-authored-by: Justin Traglia <jtraglia@pm.me>
This commit is contained in:
George Kadianakis 2023-06-01 14:58:46 +03:00 committed by GitHub
parent 6c50a43a19
commit f19cee9c3f
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1 changed files with 31 additions and 0 deletions
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31
src/c_kzg_4844.c
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@ -1656,6 +1656,33 @@ void free_trusted_setup(KZGSettings *s) {
c_kzg_free(s->g2_values);
}
/**
* Basic sanity check that the trusted setup was loaded in Lagrange form.
*
* @param[in] s Pointer to the stored trusted setup data
* @param[in] n1 Number of `g1` points in trusted_setup
* @param[in] n2 Number of `g2` points in trusted_setup
*/
static C_KZG_RET is_trusted_setup_in_lagrange_form(
const KZGSettings *s, size_t n1, size_t n2
) {
/* Trusted setup is too small; we can't work with this */
if (n1 < 2 || n2 < 2) {
return C_KZG_BADARGS;
}
/*
* If the following pairing equation checks out:
* e(G1_SETUP[1], G2_SETUP[0]) ?= e(G1_SETUP[0], G2_SETUP[1])
* then the trusted setup was loaded in monomial form.
* If so, error out since we want the trusted setup in Lagrange form.
*/
bool is_monomial_form = pairings_verify(
&s->g1_values[1], &s->g2_values[0], &s->g1_values[0], &s->g2_values[1]
);
return is_monomial_form ? C_KZG_BADARGS : C_KZG_OK;
}
/**
* Load trusted setup into a KZGSettings.
*
@ -1727,6 +1754,10 @@ C_KZG_RET load_trusted_setup(
blst_p2_from_affine(&out->g2_values[i], &g2_affine);
}
/* Make sure the trusted setup was loaded in Lagrange form */
ret = is_trusted_setup_in_lagrange_form(out, n1, n2);
if (ret != C_KZG_OK) goto out_error;
/* Compute roots of unity and permute the G1 trusted setup */
ret = compute_roots_of_unity(out->roots_of_unity, max_scale);
if (ret != C_KZG_OK) goto out_error;