Re: [PATCH v2 1/2] ecc: fix incorrect derivation of compressed points

Hi James,

On 10/10/23 09:25, James Prestwood wrote:
> The logic was inversed here and was performing a subtraction if:
>   - Y was even and type == BIT0
>   - Y was odd and type == BIT1
> 
> This is not correct according to the ANSI spec. IWD relied on this
> API but had matching incorrect logic so things "worked" up until
> a compressed point needed to be parsed from an source that
> explicitly specified the type (e.g. an ASN1 DER in DPP). All other
> uses (PWD/SAE) the point type was only used to force a subtraction
> so since both locations used the incorrect logic the points would
> compute correctly.
> ---
>   ell/ecc.c | 18 +++++++++++++++++-
>   1 file changed, 17 insertions(+), 1 deletion(-)
> 

Both applied, thanks.

Regards,
-Denis