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Improved readability for ECC signature max size calculations.

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This commit is contained in:
David Garske
2019-04-15 11:08:08 -07:00
parent bd618970c1
commit 4ee4cb2068
1 changed files with 11 additions and 9 deletions
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20
wolfcrypt/src/ecc.c
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@@ -7088,11 +7088,13 @@ int wc_ecc_sig_size_calc(int sz)
int maxSigSz = 0;
/* calculate based on key bits */
maxSigSz = (sz * 2) + (SIG_HEADER_SZ - 1) + ECC_MAX_PAD_SZ;
/* maximum possible signature header size is 7 bytes plus 2 bytes padding */
maxSigSz = (sz * 2) + SIG_HEADER_SZ + ECC_MAX_PAD_SZ;
/* if total length exceeds 127 then add 1 */
if (maxSigSz >= 127)
maxSigSz += 1;
/* if total length is less than or equal to 128 then subtract 1 */
if (maxSigSz <= 128) {
maxSigSz -= 1;
}
return maxSigSz;
}
@@ -7111,15 +7113,15 @@ int wc_ecc_sig_size(ecc_key* key)
extra byte for r and s, so add 2 */
keySz = key->dp->size;
orderBits = wc_ecc_get_curve_order_bit_count(key->dp);
/* signature header is minimum of 6 */
maxSigSz = (keySz * 2) + (SIG_HEADER_SZ - 1);
/* maximum possible signature header size is 7 bytes */
maxSigSz = (keySz * 2) + SIG_HEADER_SZ;
if ((orderBits % 8) == 0) {
/* MSB can be set, so add 2 */
maxSigSz += ECC_MAX_PAD_SZ;
}
/* if total length exceeds 127 then add 1 */
if (maxSigSz >= 127) {
maxSigSz += 1;
/* if total length is less than or equal to 128 then subtract 1 */
if (maxSigSz <= 128) {
maxSigSz -= 1;
}
return maxSigSz;