frost/secp256k1-zkp
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Eliminate harmless non-constant time operations on secret data.

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There were several places where the code was non-constant time
 for invalid secret inputs.  These are harmless under sane use
 but get in the way of automatic const-time validation.

(Nonce overflow in signing is not addressed, nor is s==0 in
 signing)
This commit is contained in:
Gregory Maxwell
2020-01-11 01:01:05 +00:00
parent 856a01d6ad
commit 34a67c773b
16 changed files with 154 additions and 101 deletions
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4
src/tests.c
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@@ -1822,7 +1822,7 @@ void run_field_misc(void) {
q = x;
secp256k1_fe_cmov(&x, &z, 0);
#ifdef VERIFY
CHECK(!x.normalized && x.magnitude == z.magnitude);
CHECK(x.normalized && x.magnitude == 1);
#endif
secp256k1_fe_cmov(&x, &x, 1);
CHECK(fe_memcmp(&x, &z) != 0);
@@ -1845,7 +1845,7 @@ void run_field_misc(void) {
secp256k1_fe_normalize_var(&q);
secp256k1_fe_cmov(&q, &z, (j&1));
#ifdef VERIFY
CHECK(!q.normalized && q.magnitude == (j+2));
CHECK((q.normalized != (j&1)) && q.magnitude == ((j&1) ? z.magnitude : 1));
#endif
}
secp256k1_fe_normalize_var(&z);