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From: Arik Sosman <me@arik.io>
In-Reply-To: <CAJowKg+DHsJR4eeHbYgwe79C-U9WZ1-iUyxNLxw9EfD6mQQLBw@mail.gmail.com>
Date: Fri, 19 Mar 2021 19:08:39 -0700
Reply-To: linuxfoundation@arik.io
Message-Id: <23C3AD3A-DB4B-4E0B-9280-2F102CA43703@arik.io>
References: <125859088-3f93e6aca40d5c3244243540270cdb84@pmq7v.m5r2.onet>
 <CAJowKg+DHsJR4eeHbYgwe79C-U9WZ1-iUyxNLxw9EfD6mQQLBw@mail.gmail.com>
To: Erik Aronesty <erik@q32.com>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] An alternative to BIP 32?
Precedence: list


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Hi Erik,

Would sha256-hmac(nonce, publicKeyPoint) still be a suitable/safe =
alternative without relying on sha3? That should at the very least =
eliminate length extension attacks.

Best,
Arik

> On Mar 19, 2021, at 6:32 PM, Erik Aronesty via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>=20
> use sha3-256.  sha256 suffers from certain attacks (length extension,
> for example) that could make your scheme vulnerable to leaking info,
> depending on how you concatenate things, etc.  better to choose
> something where padding doesn't matter.
>=20
> On Fri, Mar 19, 2021 at 7:28 PM vjudeu via bitcoin-dev
> <bitcoin-dev@lists.linuxfoundation.org> wrote:
>>=20
>> I recently found some interesting and simple HD wallet design here: =
https://bitcointalk.org/index.php?topic=3D5321992.0
>> Could anyone see any flaws in such design or is it safe enough to =
implement it and use in practice?
>> If I understand it correctly, it is just pure ECDSA and SHA-256, =
nothing else:
>>=20
>> masterPublicKey =3D masterPrivateKey * G
>> masterChildPublicKey =3D masterPublicKey + ( SHA-256( masterPublicKey =
|| nonce ) mod n ) * G
>> masterChildPrivateKey =3D masterPrivateKey + ( SHA-256( =
masterPublicKey || nonce ) mod n )
>>=20
>> Also, it has some nice properties, like all keys starting with 02 =
prefix and allows potentially unlimited custom derivation path by using =
256-bit nonce.
>> _______________________________________________
>> bitcoin-dev mailing list
>> bitcoin-dev@lists.linuxfoundation.org
>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev


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