[bitcoin-dev] Multisignature for bip-schnorr

[bitcoin-dev] Multisignature for bip-schnorr

[nakagat]

Hi all,

I wrote a multisignature procedure using bip-schnorr.

If you have time to review and give feedback, I’d really appreciate it.
Thanks in advance!

Multisignature
https://gist.github.com/tnakagawa/0c3bc74a9a44bd26af9b9248dfbe598b

Original
https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#Multisignatures_and_Threshold_Signatures

-- 
nakagawa

Re: [bitcoin-dev] Multisignature for bip-schnorr

[Erik Aronesty]

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It's cool but

- there's a lot of online steps.
- it's not a threshold system

Using a shamir scheme solves this and isn't subject to birthday attacks:

https://medium.com/@simulx/an-m-of-n-bitcoin-multisig-scheme-e7860ab34e7f



On Mon, Aug 13, 2018 at 7:08 AM nakagat via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Hi all,
>
> I wrote a multisignature procedure using bip-schnorr.
>
> If you have time to review and give feedback, I’d really appreciate it.
> Thanks in advance!
>
> Multisignature
> https://gist.github.com/tnakagawa/0c3bc74a9a44bd26af9b9248dfbe598b
>
> Original
>
> https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#Multisignatures_and_Threshold_Signatures
>
> --
> nakagawa
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

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Re: [bitcoin-dev] Multisignature for bip-schnorr

[nakagat]

Hi all,

I wrote t-of-k threshold signature procedure using bip-schnorr.

If you have time to review and give feedback, I’d really appreciate it.
Thanks in advance!

Threshold Signatures
https://gist.github.com/tnakagawa/e6cec9a89f698997dc58a09db541e1eb

Original
https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#Multisignatures_and_Threshold_Signatures

-- 
nakagawa

2018年8月7日(火) 15:35 nakagat <nakagat@gmail.com>:
>
> Hi all,
>
> I wrote a multisignature procedure using bip-schnorr.
>
> If you have time to review and give feedback, I’d really appreciate it.
> Thanks in advance!
>
> Multisignature
> https://gist.github.com/tnakagawa/0c3bc74a9a44bd26af9b9248dfbe598b
>
> Original
> https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#Multisignatures_and_Threshold_Signatures
>
> --
> nakagawa

Re: [bitcoin-dev] Multisignature for bip-schnorr

[Jonas Nick]

Your multisignature writeup appears to be vulnerable to key cancellation
attacks because the aggregated public key is just the sum of public keys (and
there is no proof of knowledge of the individual secret keys). Therefore, in a
multisignature between Alice and an attacker, the attacker can choose their key
to be -alice_key+attacker_key resulting in an aggregated key for which the
attacker can sign alone (without requiring Alice's partial signature). The
Schnorr BIP links to the MuSig paper which describes a secure key aggregation
scheme. See https://eprint.iacr.org/2018/068

On 8/7/18 6:35 AM, nakagat via bitcoin-dev wrote:
> Hi all,
> 
> I wrote a multisignature procedure using bip-schnorr.
> 
> If you have time to review and give feedback, I’d really appreciate it.
> Thanks in advance!
> 
> Multisignature
> https://gist.github.com/tnakagawa/0c3bc74a9a44bd26af9b9248dfbe598b
> 
> Original
> https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#Multisignatures_and_Threshold_Signatures
> 

Re: [bitcoin-dev] Multisignature for bip-schnorr

[nakagat]

Hi Jonas

Thank you for your comment.

I wrote a new text.
https://gist.github.com/tnakagawa/e6cec9a89f698997dc58a09db541e1eb

If you have time, please review this.
2018年9月7日(金) 17:09 Jonas Nick <jonasdnick@gmail.com>:
>
> Your multisignature writeup appears to be vulnerable to key cancellation
> attacks because the aggregated public key is just the sum of public keys (and
> there is no proof of knowledge of the individual secret keys). Therefore, in a
> multisignature between Alice and an attacker, the attacker can choose their key
> to be -alice_key+attacker_key resulting in an aggregated key for which the
> attacker can sign alone (without requiring Alice's partial signature). The
> Schnorr BIP links to the MuSig paper which describes a secure key aggregation
> scheme. See https://eprint.iacr.org/2018/068
>
> On 8/7/18 6:35 AM, nakagat via bitcoin-dev wrote:
> > Hi all,
> >
> > I wrote a multisignature procedure using bip-schnorr.
> >
> > If you have time to review and give feedback, I’d really appreciate it.
> > Thanks in advance!
> >
> > Multisignature
> > https://gist.github.com/tnakagawa/0c3bc74a9a44bd26af9b9248dfbe598b
> >
> > Original
> > https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki#Multisignatures_and_Threshold_Signatures
> >