RFR: 8285493: ECC calculation error

[Xue-Lei Andrew Fan]

On Wed, 27 Apr 2022 12:57:20 GMT, Weijun Wang <weijun at openjdk.org> wrote:

>> src/jdk.crypto.ec/share/classes/sun/security/ec/ECDSAOperations.java line 261:
>> 
>>> 259:         IntegerModuloP result = p1.asAffine().getX();
>>> 260:         b2a(result, orderField, temp1);
>>> 261:         return MessageDigest.isEqual(temp1, r);
>> 
>> I did not get the point of this update.  Is it the broken case you mentioned in the PR description?  What's the issue of the original code?
>
> Here, `result`'s modulus is `field`, and `ri`'s is `orderField`. Therefore you cannot simply subtract one from the other. One new `assert` would fail.

Got it.  It looks like a safe update.

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PR: https://git.openjdk.java.net/jdk/pull/8409