From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 651E2C013E for ; Wed, 4 Mar 2020 23:29:21 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 612E720387 for ; Wed, 4 Mar 2020 23:29:21 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JrNLu5iDniWv for ; Wed, 4 Mar 2020 23:29:19 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-40130.protonmail.ch (mail-40130.protonmail.ch [185.70.40.130]) by silver.osuosl.org (Postfix) with ESMTPS id 4B245200E5 for ; Wed, 4 Mar 2020 23:29:19 +0000 (UTC) Date: Wed, 04 Mar 2020 23:29:09 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=default; t=1583364556; bh=7VuNZcPzm9AeLJtUJsTswfGuczefb9BbpPO/zXCXTRI=; h=Date:To:From:Reply-To:Subject:In-Reply-To:References:Feedback-ID: From; b=bT/lJ2AWqawvu9a6f27lnsXAzVIoUtkHNca+TrFvSnpCnLjuF42fuldYSYTbpXREv q6VW1bHVMBcU5r41U34wrJniuRnPwVFrKNKmiH8IQcl/bTLSrPglmfqaXDctzvf/s9 WN34vKXswaCkQ4mglroElmXFr8Wh02il+ROwkums= To: Lloyd Fournier , Bitcoin Protocol Discussion From: ZmnSCPxj Reply-To: ZmnSCPxj Message-ID: In-Reply-To: References: Feedback-ID: el4j0RWPRERue64lIQeq9Y2FP-mdB86tFqjmrJyEPR9VAtMovPEo9tvgA0CrTsSHJeeyPXqnoAu6DN-R04uJUg==:Ext:ProtonMail MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [bitcoin-dev] Hash function requirements for Taproot X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Mar 2020 23:29:21 -0000 Good morning LL, Thank you very much for this work, it seems quite interesting. > 5. You can completely circumvent this result by using coin-tossing rather= than MuSig for the key generation protocol. In most cases this doesn't eve= n add any extra rounds of communication since you are doing 3-round coin to= ssing to choose the R values for the signatures that spend from the joint o= utput anyway. You can just toss your public keys in parallel. I am uncertain what you mean here by "coin-tossing". >From the comparison to MuSig, I imagine it is an interactive key generation= protocol like this: * Everybody generates fresh keypairs. * Everybody sends the hash of their pubkey to everyone else. * After receiving a hash of pubkey from everyone else, everybody sends thei= r pubkey to everyone else. * They add all their pubkeys to generate the aggregate key (and if using Ta= proot, use it as the internal key). Is that correct? In any case, the comparison to MuSig signing appears to imply interactive k= ey generation. The advantage of MuSig is that it requires no interactivity for key generat= ion of n-of-n (I am told it requires interactivity to generate k-of-n). However, it can generally be pointed out that, before you put anything into= an n-of-n, you would damn well sure want to have *some* assurance that you= can get it out later. So in general you would need coordination and interaction anyway to arrange= getting into an n-of-n in the first place. On the other hand, it would be best to have at least some minimum of privac= y by always interacting over Tor and having a Tor .onion address, which has= absolutely horrid latency because human beings cry when peeling onions. So in general reducing the latency by reducing communication rounds is bett= er in general. Counter to this, assuming you use an n-of-n in an offchain protocol of some= sort, the number of communication rounds to generate the aggregate key may= be dwarfed by the total number of communication rounds to create signature= s to update the offchain protocol. Counter counter to this is that one plan for reducing communications rounds= for creating signatures during offchain operation is to (haha) use a Tapro= ot with an n-of-n internal key and a tapscript that has n `OP_CHECKSIG` ope= rations, so that for normal operation you just toss individual signatures a= t each other but at termination of the offchain protocol you can do the hea= vy MuSig-style signing with the n-of-n aggregate key. Regards, ZmnSCPxj