linux-kernel - Re: [PATCH 0/7] crypto: add eddsa support for x509(Internet mail)

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Date:   Mon, 17 May 2021 14:21:06 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     herberthbli(李弘博) 
        <herberthbli@...cent.com>
Cc:     Hongbo Li <herbert.tencent@...il.com>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "tianjia.zhang@...ux.alibaba.com" <tianjia.zhang@...ux.alibaba.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/7] crypto: add eddsa support for x509(Internet mail)

On Thu, May 13, 2021 at 02:44:07PM +0000, herberthbli(李弘博) wrote:
> 在 2021/5/13 3:12, Eric Biggers 写道:
> 
> On Wed, May 12, 2021 at 10:04:07PM +0800, Hongbo Li wrote:
> 
> 
> From: Hongbo Li <herberthbli@...cent.com><mailto:herberthbli@...cent.com>
> 
> This series of patches add support for x509 cert signed by eddsa,
> which is described in RFC8032 [1], currently ed25519 only.
> 
> 
> 
> It would be helpful to explain how this is related to the kernel's existing
> Curve25519 support.
> 
> - Eric
> 
> 
> Curve25519 is an elliptic curve used for key agreement(ECDH). It is a Montgomery curve.
> 
> Edwards25519 is a twisted Edwards curve and birationally equivalent to Curve25519, the
> birational maps are described in rfc7748 section 4.1.
> https://datatracker.ietf.org/doc/html/rfc7748#section-4.1
> 
> 
> Ed25519 is a Digital Signature Algorithm over Edwards25519.
> 

Sure, but what does that mean in terms of code.  Can you reuse any of the code,
and if not why not?  I *think* the answer is no, but this is a common point of
confusion, so it would be helpful to properly explain this...

- Eric