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#627: M1631573

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Cameron Kaiser 2020-10-01 13:13:56 -07:00
parent 2373458b58
commit 0abd0fc5d5
1 changed files with 0 additions and 21 deletions
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21
security/nss/lib/freebl/ec.c
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@ -723,27 +723,6 @@ ECDSA_SignDigestWithSeed(ECPrivateKey *key, SECItem *signature,
goto cleanup;
}
/*
** We do not want timing information to leak the length of k,
** so we compute k*G using an equivalent scalar of fixed
** bit-length.
** Fix based on patch for ECDSA timing attack in the paper
** by Billy Bob Brumley and Nicola Tuveri at
** http://eprint.iacr.org/2011/232
**
** How do we convert k to a value of a fixed bit-length?
** k starts off as an integer satisfying 0 <= k < n. Hence,
** n <= k+n < 2n, which means k+n has either the same number
** of bits as n or one more bit than n. If k+n has the same
** number of bits as n, the second addition ensures that the
** final value has exactly one more bit than n. Thus, we
** always end up with a value that exactly one more bit than n.
*/
CHECK_MPI_OK(mp_add(&k, &n, &k));
if (mpl_significant_bits(&k) <= mpl_significant_bits(&n)) {
CHECK_MPI_OK(mp_add(&k, &n, &k));
}
/*
** ANSI X9.62, Section 5.3.2, Step 2
**