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[202.12.124.144]) by gmr-mx.google.com with ESMTPS id 6a1803df08f44-88652aeb634si1899466d6.8.2025.11.29.01.25.41 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 29 Nov 2025 01:25:41 -0800 (PST) Received-SPF: pass (google.com: domain of pete@petertodd.org designates 202.12.124.144 as permitted sender) client-ip=202.12.124.144; Received: from phl-compute-01.internal (phl-compute-01.internal [10.202.2.41]) by mailfout.stl.internal (Postfix) with ESMTP id 1768F1D00306; Sat, 29 Nov 2025 04:25:41 -0500 (EST) Received: from phl-mailfrontend-01 ([10.202.2.162]) by phl-compute-01.internal (MEProxy); Sat, 29 Nov 2025 04:25:41 -0500 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeeffedrtdeggddvhedvtdelucetufdoteggodetrf dotffvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfurfetoffkrfgpnffqhgenuceu rghilhhouhhtmecufedttdenucenucfjughrpeffhffvvefukfhfgggtuggjsehgtderre dttddvnecuhfhrohhmpefrvghtvghrucfvohguugcuoehpvghtvgesphgvthgvrhhtohgu ugdrohhrgheqnecuggftrfgrthhtvghrnhepledvleelffdtudekudffjefgfeejueehie elfedtgfetudetgeegveeutefhjedtnecuffhomhgrihhnpehpvghtvghrthhouggurdho rhhgnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepph gvthgvsehpvghtvghrthhouggurdhorhhgpdhnsggprhgtphhtthhopeefpdhmohguvgep shhmthhpohhuthdprhgtphhtthhopegvthhhfehrshesghhmrghilhdrtghomhdprhgtph htthhopehlrghishhsvgiirdhfrghirhgvrdgsthgtsehgmhgrihhlrdgtohhmpdhrtghp thhtohepsghithgtohhinhguvghvsehgohhoghhlvghgrhhouhhpshdrtghomh X-ME-Proxy: Feedback-ID: i525146e8:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Sat, 29 Nov 2025 04:25:40 -0500 (EST) Received: by localhost (Postfix, from userid 1000) id 59C249FD56; Sat, 29 Nov 2025 09:25:35 +0000 (UTC) Date: Sat, 29 Nov 2025 09:25:35 +0000 From: Peter Todd To: Ethan Heilman Cc: Lazy Fair , bitcoindev@googlegroups.com Subject: Re: [bitcoindev] A safe way to remove objectionable content from the blockchain Message-ID: References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="yN/NKZ+VTyslAqN5" Content-Disposition: inline In-Reply-To: X-Original-Sender: pete@petertodd.org X-Original-Authentication-Results: gmr-mx.google.com; dkim=pass header.i=@messagingengine.com header.s=fm1 header.b=dTnfpdx+; spf=pass (google.com: domain of pete@petertodd.org designates 202.12.124.144 as permitted sender) smtp.mailfrom=pete@petertodd.org 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 (/) --yN/NKZ+VTyslAqN5 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline On Thu, Nov 20, 2025 at 04:21:33PM -0500, Ethan Heilman wrote: > I'm not convinced your hash function approach fully does what you want it > to, although it does seem doable with some additional constraints. > > There is a solution that does everything you want it and more, ZKPs. > > ZKP (Zero Knowledge Proofs) can prove that some data X hashes to some hash > output Y while keeping the actual value X secret. Thus, everyone can be > convinced that H(X) = Y even if X is deleted and no one knows what the > value X was. > > Even more exciting, ZKPs can prove the correctness and validity of the > entire Bitcoin blockchain. Thus storing old transactions is > no longer needed to convince others that the chain is correct. This would > remove any harmful data. Zerosync in 2017 compressed Bitcoin's blockchain > into a 800 KB proof [0] which is constant size regardless of the number of > transactions or bytes compressed. This approach does not require any > changes to Bitcoin and you could implement a Bitcoin full node today that > supports this. > > We have a solution to solve the problem of harmful data on the blockchain > since 2017. It just requires time, money and motivated people to work on it. Rather than being a solution, the technology behind Zerosync is a potential threat to Bitcoin. The problem is that Bitcoin fundamentally requires proof-of-publication to be decentralized and censorship resistant; a related problem is that HTLCs (and thus Lightning) fundamentally requires proof-of-publication to work at all. For Bitcoin mining to remain decentralized, blocks need to be widely propagated in a form suitable for creating new blocks. ZKP/Zerosync makes it possible to prove that a block hash and all prior blocks follow the protocol rules and were thus valid. However, valid block hashes alone are insufficient to mine on top of because they do not contain the UTXO set data necessary to mine a new block. Why do miners have an incentive to distribute the blocks they find? Ultimately because doing so is necessary for the coins they mined to be valuable. But if full nodes can be convinced of the validity of coins without full block contents --- thus allowing those coins to be sold --- that weakens the incentives to distribute block data in a form that allows other miners to mine. With regard to HTLCs/Lightning, HTLCs rely on a proof-of-publication to be secure: for the HTLC to be redeemed, the redeemer *must* publish the pre-image in the Bitcoin chain, allowing the other party relying on the HTLC to recover the pre-image. Again, ZKP/Zerosync weakens this security, as the validity of the transaction spending the HTLC can be proven without actually making the pre-image available. Rather than presenting ZKP/Zerosync as a solution to the "harmful data" problem, we should in fact be researching ways to defeat ZKP/Zerosync entirely. We need a consensus protocol where the only way to fully validate a block is to actually have the entire block contents. As for "harmful data", that is a challenge to be solved legally/politically. -- https://petertodd.org 'peter'[:-1]@petertodd.org -- 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 email to bitcoindev+unsubscribe@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/aSq8Dya6-lzYB35t%40petertodd.org. --yN/NKZ+VTyslAqN5 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE0RcYcKRzsEwFZ3N5Lly11TVRLzcFAmkqvAUACgkQLly11TVR LzcmbxAAwvKw8/Z/6+q6fz/97Y4Owz3gRTkfBcxJ1Rm3R0qEHsb/DT8N+8XKVYxq bceU36OFo13uQH0gBdZuHzB//5ulT/IS/PcJF8sRoLsD0bgV+PhJ8PlZLWVQE1kW KMRHpptjlUKoXjJTV9hrW4QP8a1uCLEPKl0ZJ6jNEW2r9UUaq1eWZyBV76eoECn2 HIFBtOWIN2kEGwlPKMVoTKjgZpLXdK3rBzByd/6YtQx95Lxc/9lCwAfw+UoBZm1b gyH9YLEkDa2WqkVoTac32ctOrJQPkAv3ejZ9pmCDtgNNmO7ZyPMtpMcVcOF8warV gtAhOuXAQdGVJl4neIS2RiLvM1fjvIueO5LEvbmYtMbgH/+LGoXldvLBUIrkDdOF +Val7v6ciVZ2X7umtsLT00dq+JSHn4MPNHb8m78bEKHjEXzNuQ/DutpWMPWAW4aS u1soCU+BPpe6b3nah4se+DjkRWUHTmV7tXMu6+Vm6fw0mYN79Qakc1/pdnbHtHTP 2wy8nHOrfGAIXUf7jMSRpkOfausM4ZnKdaDquWFCPDovjOHXMsHOXufiPCcK5MRS 32li+vNwyzf+9ZVkcv08DwCHCZZQPpv13Nhvfxw3KW3/mc+SQyu57ilQPK/1nTue vnew1B8snhtXqnXzGvkgbYNSnhHV/l9OZ+XofXBUwGiiqc4vECI= =08v3 -----END PGP SIGNATURE----- --yN/NKZ+VTyslAqN5--