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[73.100.212.73]) by smtp.gmail.com with ESMTPSA id af79cd13be357-910bad2dd8esm713748285a.19.2026.05.15.17.58.49 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 May 2026 17:58:50 -0700 (PDT) From: To: "'Bitcoin Development Mailing List'" Cc: "'Fabian'" , "'Anthony Towns'" References: <19616822-8a03-4de1-99be-72d50479208fn@googlegroups.com> <02c201dce227$e808e050$b81aa0f0$@voskuil.org> In-Reply-To: Subject: RE: [bitcoindev] Re: [BIP Draft] P2P UTXO Set Sharing Date: Fri, 15 May 2026 20:58:48 -0400 Message-ID: <002301dce4cf$27bc3040$773490c0$@voskuil.org> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQE9V3UU3txRcB+TPknCl7kBT2x4HgI+SqEvAnGwGX0CLAFOzQILAHoxtwej/RA= Content-Language: en-us X-Original-Sender: eric@voskuil.org X-Original-Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@voskuil.org header.s=google header.b=dohOqu5h; spf=pass (google.com: domain of eric@voskuil.org designates 2607:f8b0:4864:20::736 as permitted sender) smtp.mailfrom=eric@voskuil.org; dara=pass header.i=@googlegroups.com Precedence: list Mailing-list: list bitcoindev@googlegroups.com; contact bitcoindev+owners@googlegroups.com List-ID: X-Google-Group-Id: 786775582512 List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , X-Spam-Score: -0.8 (/) > From: Anthony Towns > On Tue, May 12, 2026 at 11:56:33AM -0400, eric@voskuil.org wrote: > > > AssumeUTXO is a UX improvement for those interested in running a > > > fully validating node. The option to get started in a very limited > > > amount of time [...] > > It's not at all clear to me how this is a UX improvement. Get started d= oing > what? >=20 > Getting started validating blocks and transactions at the current tip; ie > receiving payments. Receiving payments without having validated is an exceedingly unwise scenar= io, and not worthy of protocol support. If you have not fully validated every block in history, you have not valida= ted at all. The validity of a block requires the validity of all prior bloc= ks. There seems to be a common misapprehension that using a trusted utxo store = is something akin to SPV. This is not the case. A node/wallet could certain= ly also implement SPV and use it while downloading/validating, though that = eliminates the use case for trusted utxo state. Using a trusted utxo store for transacting is equivalent to a fully trustin= g wallet. The person is 100% trusting that the state of their node is valid= - having not validated any of it until having validated all of it. Accepti= ng this as a matter of protocol is irresponsible. If you want a reduced (vs. zero) level of security while downloading and va= lidating the chain, I suggest implementing an SPV wallet that transitions t= o a full node wallet after downloading and validating the full chain. > Obtaining the full Bitcoin blockchain currently requires downloading abou= t > 600GB of data. At 250Mbps with perfectly well-behaved peers, that's a bit > under 7 hours. At the consumer level, bandwidth seems to be the bottlenec= k, > with modern PCs being able to validate the blockchain in about that time. Let's look at the trend: May 2016 --------------------------------------------------------------------------- Blockchain size: ~80 GB Median U.S. broadband speed: 39 Mbps Download time: 4 hours 33 minutes 80 =C3=97 8,000 =3D 640,000 Mb 640,000 =C3=B7 39 =E2=89=88 16,410 seconds 16,410 =C3=B7 3,600 =E2=89=88 4.558 hours (4 hours 33 minutes) May 2021 --------------------------------------------------------------------------- Blockchain size: 343.5 GB Median U.S. broadband speed: 100 Mbps Download time: 7 hours and 38 minutes 343.5 =C3=97 8,000 =3D 2,748,000 Mb 2,748,000 =C3=B7 100 =3D 27,480 seconds 27,480 =C3=B7 3,600 =E2=89=88 7.633 hours (7 hours and 38 minutes) May 2026 --------------------------------------------------------------------------- Blockchain size: 739.2 GB Median U.S. broadband speed: 308 Mbps Download time: 5 hours and 20 minutes 739.2 =C3=97 8,000 =3D 5,913,600 Mb 5,913,600 =C3=B7 308 =3D 19,200 seconds 19,200 =C3=B7 3,600 =3D 5.333=E2=80=A6 hours (5 hours and 20 minutes) --------------------------------------------------------------------------- Despite a 4x max block size increase in 2016, download time is *decreasing*= . It only increased in early years because blocks went from empty to ~full (m= edian block ~1MB in 2016), coupled with segwit 4MB limit impact. > AssumeUTXO significantly reduces the download requirement, with the utxo > snapshot at block 935000 being under 9GB. At 100Mbps with perfectly well- > behaved peers, that's about 15m to download. Adding in another 8GB-34GB > of actual block data to download (assuming that the utxo snapshot people = use > will be between 4 and 17 weeks out of date) brings that up to 30 minutes = to > an hour. Downloading an additional 9GB only increases the total download requirement= /time. What has been increasing is the perception of increased block data exceedin= g Moore's Law. This perception has fed the spam debacle. This perception is= rooted in the reality that sequential indexation (even without validation)= does not (cannot) fully take advantage of advancing hardware. This is an i= mplementation issue. Chain growth is linearly bounded. Hardware growth at a given cost is expone= ntial. Even Satoshi reasoned this out. What he didn't do in his prototype w= as provide a scalable implementation - he left that to us. Necessary downlo= ad and validation time/cost is shrinking. Eventually downloading and valida= ting the chain will be as cheap as texting a video clip has become. It wasn= 't long ago that too was unthinkable. On a fast home Internet today, on the same machine I've been developing on = since 2017, the full chain can be downloaded and fully validated in under 5= hours. That's less time than it took almost 10 years ago on the same machi= ne - and my real Internet cost today is about half what it was at that time= . So I reiterate my NACK. This is a very unwise idea, without justification f= or network protocol integration. Best, Eric --=20 You received this message because you are subscribed to the Google Groups "= Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to bitcoindev+unsubscribe@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/= 002301dce4cf%2427bc3040%24773490c0%24%40voskuil.org.