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SP int math; submod fix

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Fix for sp_submod() to reduce by modulus when a or b are equal to
modulus as well as when greater.
This commit is contained in:
Sean Parkinson
2022-06-30 08:53:25 +10:00
parent f2acaa8ee9
commit 0159f17692
1 changed files with 6 additions and 8 deletions
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14
wolfcrypt/src/sp_int.c
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@ -6494,13 +6494,13 @@ int sp_submod(sp_int* a, sp_int* b, sp_int* m, sp_int* r)
ALLOC_SP_INT_ARRAY(t, used, 2, err, NULL); ALLOC_SP_INT_ARRAY(t, used, 2, err, NULL);
if (err == MP_OKAY) { if (err == MP_OKAY) {
if (_sp_cmp(a, m) == MP_GT) { if (_sp_cmp(a, m) != MP_LT) {
err = sp_mod(a, m, t[0]); err = sp_mod(a, m, t[0]);
a = t[0]; a = t[0];
} }
} }
if (err == MP_OKAY) { if (err == MP_OKAY) {
if (_sp_cmp(b, m) == MP_GT) { if (_sp_cmp(b, m) != MP_LT) {
err = sp_mod(b, m, t[1]); err = sp_mod(b, m, t[1]);
b = t[1]; b = t[1];
} }
@ -6508,14 +6508,12 @@ int sp_submod(sp_int* a, sp_int* b, sp_int* m, sp_int* r)
if (err == MP_OKAY) { if (err == MP_OKAY) {
if (_sp_cmp(a, b) == MP_LT) { if (_sp_cmp(a, b) == MP_LT) {
err = sp_add(a, m, t[0]); err = sp_add(a, m, t[0]);
if (err == MP_OKAY) { a = t[0];
err = sp_sub(t[0], b, r);
}
}
else {
err = sp_sub(a, b, r);
} }
} }
if (err == MP_OKAY) {
err = sp_sub(a, b, r);
}
#if 0 #if 0
if (err == MP_OKAY) { if (err == MP_OKAY) {