RFR: 8285493: ECC calculation error

[Weijun Wang]

On Wed, 27 Apr 2022 06:28:27 GMT, Xue-Lei Andrew Fan <xuelei at openjdk.org> wrote:

>> Only numbers from the same modular fields can be involved in arithmetic calculations. Add `assert` to guarantee this.
>> 
>> Also, found one broken case and rewrote it.
>
> 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.

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