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Re: [CFRG] EdDSA converting to x25519 - not

John Mattsson <john.mattsson@ericsson.com> Sat, 01 April 2023 00:41 UTC

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From: John Mattsson <john.mattsson@ericsson.com>
To: James Muir <muir.james.a@gmail.com>, "cfrg@irtf.org" <cfrg@irtf.org>
Thread-Topic: [CFRG] EdDSA converting to x25519 - not
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Date: Sat, 01 Apr 2023 00:41:35 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/cfrg/6Qy4z24Qx_v8tk0MPD2suf_OhAI>
Subject: Re: [CFRG] EdDSA converting to x25519 - not
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Hi,

Group OSCORE does exactly this (as an option)
https://datatracker.ietf.org/doc/draft-ietf-core-oscore-groupcomm/

For the setting in Group OSCORE it has been proven that this is secure.
https://eprint.iacr.org/2021/509

Cheers,
John

From: CFRG <cfrg-bounces@irtf.org> on behalf of James Muir <muir.james.a@gmail.com>
Date: Saturday, 1 April 2023 at 04:33
To: cfrg@irtf.org <cfrg@irtf.org>
Subject: Re: [CFRG] EdDSA converting to x25519 - not
On 2023-03-30 09:57, Robert Moskowitz wrote:
> So I DID have it right my first 2 readings.  There are library calls to
> do this conversion.

Rene Struik has authored a very good document that includes discussions
of maps between related curves, in greater detail than RFC 7748:

   https://datatracker.ietf.org/doc/draft-ietf-lwig-curve-representations/

In Appendix E, the curves edwards25519 and curve25519 are discussed.

-James M

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