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Date: Thu, 13 Feb 2025 18:16:04 +0100
Message-ID: <CAEKnhAGWXg47YDLoWNi1hTRddUsoJmNB3q9fH5==1WSVvm==1g@mail.gmail.com>
Subject: Re: [PHP-DEV] Update OpenSSL Extension to Support KEMs
To: Paragon Initiative Enterprises Security Team <security@paragonie.com>
Cc: PHP Internals <internals@lists.php.net>
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From: bukka@php.net (Jakub Zelenka)

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>
>
> to include PHP functions in the OpenSSL extension that look like this:
>>
>> function openssl_kem_encaps(OpenSSLAsymmetricKey $pk): array;
>>
>
> The name should be more openssl_pkey_encapsulate
>
>

I just did a bit more checking and we should consider having required kem
operation as selected by EVP_PKEY_CTX_set_kem_op . There are currently just
single operations (e.g. RSAVE for RSA and DHKEM for others). OpenSSL chose
not set default which has got some good reasoning described in
https://github.com/openssl/openssl/pull/12750 . I haven't checked out how
it is in the current PQC (whether there are already more operations) but
possibly there might be more in the future. This would make the function
harder to use as one would need to know the operations but setting our own
defaults prove usually not ideal in the long term (it's hard to change
those defaults (BC break) if there are issues with them) so it might be
just better to leave that to user space maybe. Or it might be worth to
check what other implementations do. It should certainly have some
consideration.

Regards

Jakub

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<div dir=3D"ltr"><div class=3D"gmail_quote gmail_quote_container"><blockquo=
te class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px =
solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div class=3D"gma=
il_quote"><div><br></div><blockquote class=3D"gmail_quote" style=3D"margin:=
0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">=
<div dir=3D"ltr"><div><div style=3D"font-family:monospace,monospace">to inc=
lude PHP functions in the OpenSSL extension that look like this:</div><div =
style=3D"font-family:monospace,monospace"><br></div><div style=3D"font-fami=
ly:monospace,monospace">function openssl_kem_encaps(OpenSSLAsymmetricKey $p=
k): array;</div></div></div></blockquote><div><br></div><div>The name shoul=
d be more openssl_pkey_encapsulate</div><div>=C2=A0<br></div></div></div></=
blockquote><div><br></div><div>I just did a bit more checking and we should=
 consider having required kem operation as selected by=C2=A0EVP_PKEY_CTX_se=
t_kem_op . There are currently just single operations (e.g. RSAVE for RSA a=
nd DHKEM for others). OpenSSL chose not set default which has got some good=
 reasoning described in <a href=3D"https://github.com/openssl/openssl/pull/=
12750">https://github.com/openssl/openssl/pull/12750</a> . I haven&#39;t ch=
ecked out how it is in the current PQC (whether there are already more oper=
ations) but possibly there might be more in the future. This would make the=
 function harder to use as one would need to know the operations but settin=
g our own defaults prove usually not ideal in the long term (it&#39;s hard =
to change those defaults (BC break) if there are issues with them) so it mi=
ght be just better to leave that to user space maybe. Or it might be worth =
to check what other implementations do. It should certainly have some consi=
deration.</div><div><br></div><div>Regards</div><div><br></div><div>Jakub</=
div></div></div>

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