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From: Denis Kenzior <denkenz@gmail.com>
To: James Prestwood <prestwoj@gmail.com>, ell@lists.linux.dev
Subject: Re: [PATCH v2 1/2] ecc: fix incorrect derivation of compressed points
Date: Wed, 11 Oct 2023 09:55:56 -0500	[thread overview]
Message-ID: <bc8f7101-6deb-4016-8244-3ecdd13869aa@gmail.com> (raw)
In-Reply-To: <20231010142506.261152-1-prestwoj@gmail.com>

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


      parent reply	other threads:[~2023-10-11 14:56 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-10 14:25 [PATCH v2 1/2] ecc: fix incorrect derivation of compressed points James Prestwood
2023-10-10 14:25 ` [PATCH v2 2/2] unit: update test-ecc with compressed point bug fix James Prestwood
2023-10-11 15:26   ` Denis Kenzior
2023-10-11 14:55 ` Denis Kenzior [this message]

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