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From: Lloyd Fournier <lloyd.fourn@gmail.com>
Date: Sun, 22 Mar 2020 16:51:59 +1100
Message-ID: <CAH5Bsr2A7BepO9qYdL=Vzeajm1ZpoyH7-6AjLjcNDA8k5Qq0fA@mail.gmail.com>
To: Pieter Wuille <pieter.wuille@gmail.com>, 
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] BIP 340 updates: even pubkeys,
	more secure nonce generation
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* To protect against differential power analysis, a different way of
> mixing in this randomness is used (masking the private key completely
> with randomness before continuing, rather than hashing them together,
> which is known in the literature to be vulnerable to DPA in some
> scenarios).
>

I think citation for this would improve the spec.

I haven't studied these attacks but it seems to me that every hardware
wallet would be vulnerable to them while doing key derivation. If the
attacker can get side channel information from hashes in nonce derivation
then they can surely get side channel information from hashes in HD key
derivation. It should actually be easier since the master seed is hashed
for anything the hardware device needs to do including signing.

is this the case?

LL

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left:1px solid rgb(204,204,204);padding-left:1ex">* To protect against diff=
erential power analysis, a different way of<br>
mixing in this randomness is used (masking the private key completely<br>
with randomness before continuing, rather than hashing them together,<br>
which is known in the literature to be vulnerable to DPA in some<br>
scenarios).<br></blockquote><div><br></div><div>I think citation for this w=
ould improve the spec.</div><div><br></div><div>I haven&#39;t studied these=
 attacks but it seems to me that every hardware wallet would=C2=A0be vulner=
able to them while doing key derivation. If the attacker can get side chann=
el information from hashes in nonce derivation then they can surely get sid=
e channel information from hashes in HD key derivation. It should actually =
be easier since the master seed is hashed for anything the hardware device =
needs to do including signing.</div><div><br></div><div>is this the case?</=
div><div><br></div><div>LL</div></div></div>

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