Re: [Cfrg] Curve25519 lacks private/public homomorphism?

Dmitry Khovratovich <khovratovich@gmail.com> Tue, 05 February 2019 21:18 UTC

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From: Dmitry Khovratovich <khovratovich@gmail.com>
Date: Tue, 5 Feb 2019 22:18:02 +0100
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To: Tony Arcieri <bascule@gmail.com>
Cc: Dan Brown <danibrown@blackberry.com>, cfrg@irtf.org
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Subject: Re: [Cfrg] Curve25519 lacks private/public homomorphism?
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>
> Using addition instead of multiplication is the BIP32 method, and it has
> the same problems. See the Ed25519-BIP32 key recovery attack here:
>
> https://forum.web3.foundation/t/key-recovery-attack-on-bip32-ed25519/44
>

This is not an attack on Ed25519-BIP32, as it violates the protocol
description in having the hierarchy of 2^30 levels instead of permitted
2^20. In such a way a secret key publication can be called an "attack".



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> Tony Arcieri
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